About to buy new Batteries - not sure if my set up is correct to start with

obbaobba Registered Users Posts: 14
Hi all,
I started with a small solar shed light setup and now it's bigger, much to my wifes dismay. All DIY and this is my first post asking for professional help, due to the cost involved in buying new batteries. All my work has been from what i have read from the net - and i've been told many conflicting stories.

Info overload here i'm afraid :) Just feel i have to say it in one go and try not to miss something obvious to you guys.

So as i stand my original 12xTrojan T105's (6 Banks of 12v), have all died within 4 years and i've got some 2nd hand ones dying now.

We have a 1000W PSW Inverter to the house. 12v into 240v.
We have 2 x 240v feeds, that power normal lights, and every device that is on 24/7 (Alarm clocks, phone/power adaptors for charging etc, fax machine, two Laptops, PC modem/routers etc, One beer bar fridge, other things like photo frames, 4 STB's, security recorder and 4 cameras.
We have a Plasmatronics 60Amp reg and also run 3 x 12volt feeds into the house to power native 12v CFL (12W) lights installed in all the bedrooms, hallway, kitchen, dining rooms etc
And a battery back of 12 T105's - in series and parallel to provide a 12volt system.
I am using very thick cables to connect all the associated terminals etc.

One website, can't recall now, said that the charging and inv MUST be on the same poles!! I was told to have them diagonally opposite.


In the past the house has ran for about 3 days on its battery supply (stuff as described above). I don't know if that's laughable or good.

I have a volt meter in the house and i see the batts goto 14.5v right at the end of the day (on a good sunny day). The batteries seem to struggle at the 13.5v mark for ages (middle of the day), then climb upwards. Then at night (7pm), it will settle down down to 12.5v and sort of hang around that. At about 11pm it might be down to 12.3v, then the 12v lights in the house are turned off for beddibyes.
In the morning it is about 12.2v.
But lately (and as now and when things were going bad), the voltage would down to 11.5v in the mornings and then the 12v feed into the house would shut off and then soon after the inverter would start screaming (low v's).


On a good summer day 25c i have seen 450Amps go into the batteries (The highest ever 500). Normal days 300Amps, low/cloudy days 120Amps.


I admit to making stupid mistakes with my orig T105's. Used a 20amp controller with 4 panels at the start (yes, stupid!), I used car chargers to charge them when they were low. I forgot to top them up with water (could see the plates).
Now i have many more BP80watt panels! ;) and a 60Amp reg.
For external Boosting on very bad days i use a regulated 40amp power supply set at 14.4volts.
And one by they started failing - the charge never seemed to hold as it used to! The battery voltage in the morning was getting lower and lower! Then i found that some batteries were very warm!
Then it clicked that a lot of solar input was going to them and through the night the other batteries were draining into them!!!


So now after learning the hard way, i am ready to purchase some more batteries. But i have concerns if the 'final' set up is actually correct and if it is correct to look after the batteries for the long term.

I'm not sure if i need 12 x 6vs or just go with 12vs. Gel or Wet?
I guess my most important question is do i have enough amperage input to look after the batteries. Should i use less batteries but get full charge, so it will last longer than having 3/4charge in more batteries?


I include a very basic picture of my setup. Leads from Reg 2-3mtrs. Leads to INV 2mtrs. Bridging cable for batt series approx 20cm, bridging for batt parallel approx 25cm - so the battery bank is tightly packed with about 10mm air gap.

http://i202.photobucket.com/albums/aa36/obba41/SolarBatterySetup.jpg


I get some terminals with the green corrosion 'fungus' growth on some terminals - why do i get that even if they have been cleaned?
I use terminal cleaner and started to use a terminal protector (put's a brown gunge covering on).
I use Two Megapulses and have used them to 'stop sulphation'. These are wired across to 6 banks each.

Sorry for the long post. I found this forum by looking up 6v vs 12v setups and it's clear that this site has a lot of people who know a lot more than i do ;)

Regards,
Alan.
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Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Welcome to the forum Alan,
    obba wrote: »
    Hi all,
    I started with a small solar shed light setup and now it's bigger, much to my wifes dismay.

    You cannot win this one... Keep spouse happy. First rule of Wind Sun Forum... Second is don't talk about Wind Sun Forum.
    All DIY and this is my first post asking for professional help, due to the cost involved in buying new batteries. All my work has been from what i have read from the net - and i've been told many conflicting stories.

    Sometimes, honest disagreements--Other times not looking at the big picture and getting lost in the details... I always like to start with big picture, then push down into questions.

    Info overload here i'm afraid :) Just feel i have to say it in one go and try not to miss something obvious to you guys.
    So as i stand my original 12xTrojan T105's (6 Banks of 12v), have all died within 4 years and i've got some 2nd hand ones dying now.
    From your link below, you are wiring them correctly--But, possibly are falling in the the trap of a massively parallel battery bank... Besides lots of electrical connections and cells to check for water levels--It can be difficult to get batteries to share current properly

    Batteries have very low internal resistance--And any slight change in resistance (dirty connection, slowly rotting wire wire, failing cell in battery) will direct current away from those strings.

    And, believe it or not, the "good connection" (low resistance, everything work well) many times will end up handling 2x or more of a strings "share" of the current--Which can over heat wiring/connections and/or cause a parallel string to cycle more than the rest, and wear out sooner.

    Also--Failures in parallel strings are hard to find. You have an open cell/or open wiring connection that is not passing its share of current--With 5 other strings, how do you know that? Eventually the batteries in that string will self discharge and sulfate.

    Or, you have a shorted cell, which then causes excessive charging current to flow in a string--Overcharging the rest of the cells and possibly discharging the rest of the bank...

    There are other issues too, but my personal recommendation is to go with no more than 2-3 parallels strings of batteries. Pick larger batteries instead (instead of a 220 AH 6 volt battery, get a 660 AH 2 volt one instead (single 2 volt cell). Now, instead of three strings of 220 AH batteries, you have one string of 660 AH cells. And the "cell/6 volt" batteries are still the same weight (move around by one person).

    Also, with parallel strings, you should have a fuse/breaker per string--So that short in one string (dropped tool) does not get fed "unlimited" current from the other 5 strings. (adding fuses/breaker per string adds cost and failure points too).

    So, big picture time--What is your Watt*Hours (or Amp*Hours * voltage) needs per day? I like to size the battery bank based on real power needs (no bigger/smaller bank than needed). In the olden days, people would add massive amounts of batteries, when the problem was not enough solar panels to sustain daily power usage/battery recharging (in olden days, solar panels where $5-$10+ per watt, today $2 per watt or less is very common).
    We have a 1000W PSW Inverter to the house. 12v into 240v.
    We have 2 x 240v feeds, that power normal lights, and every device that is on 24/7 (Alarm clocks, phone/power adaptors for charging etc, fax machine, two Laptops, PC modem/routers etc, One beer bar fridge, other things like photo frames, 4 STB's, security recorder and 4 cameras.
    We have a Plasmatronics 60Amp reg and also run 3 x 12volt feeds into the house to power native 12v CFL (12W) lights installed in all the bedrooms, hallway, kitchen, dining rooms etc

    That is a very reasonable sized inverter... With a bank that size, seeing 2kW or larger 12 volt inverters is not uncommon (and a problem--Too large of inverter draws lots of current).

    You do have a choice, if your peak loads/surge current is low, but you have many hours of "on time", you can stay at 12 volts with your inverter--Or look at a 24 or 48 volt inverter... A 24 volt inverter would cut you from 6 to 3 parallel strings with the same batteries--just a rewire job--And cut the cable diameter/awg by 1/2...

    Also, solar charge controllers are typically rated at, for example, 60 amps of output current--That is 60 amps at 12 volts, 24 volts, or 48 volts...

    A 60 amp controller can "manage" a 2x larger array at 24 volts or 4x larger (wattage) array at 48 volts--So you have a potential cost savings/simplifiying with a higher voltage battery bank (regarding solar charge controller).

    Big picture thing again--Like to size bank WH, inverter wattage, and array wattage first, without looking at battery bank voltage... Then when we know the power needed, make the 12/24/48 volt choice.

    You may be stuck at 12 volts with your DC pumps... But there are some nice 24 VDC pumps too... And 48 opens you up to much larger well pumps (Grundfos and others).
    And a battery back of 12 T105's - in series and parallel to provide a 12volt system.
    I am using very thick cables to connect all the associated terminals etc.

    Yea--The bane of a 12 volt system, heavy cables to carry current, and heavier yet to get down to ~0.5 volt maximum drop so inverter does not shut down when battery bank gets a little discharged and/or a heavy starting or surge load.
    One website, can't recall now, said that the charging and inv MUST be on the same poles!! I was told to have them diagonally opposite.

    From looking at your link/drawing--You are fine with what you are doing... It does not matter in your case--There are two "correct points" to attach your inverter and charge controller. You might get slightly less voltage drop if both inverter and charge controller are attached to the same bus points--But I think we are talking very small "benefits" here--I would not change it assuming all is working well.
    In the past the house has ran for about 3 days on its battery supply (stuff as described above). I don't know if that's laughable or good.

    Nominal recommendations around here... 1-3 days of battery usage (no-sun), and 50% maximum discharge (for longer battery life). Nominally, 2 days of no-sun and 50% maximum discharge seems to work well (4 days from full charge to dead).

    I don't know if you are taking the bank "dead" (discharging below 50% often reduces battery life). Discharging below 20% state of charge can kill one or more battery cells (the weakest sell will go to zero volts and then begin to reverse charge--most battery chemistries will be destroyed with reverse charging).

    So, if your bank was in good shape -- It may run 4 days to "dead" which is right in the "sweet spot" of our design rules of thumb.
    I have a volt meter in the house and i see the batts goto 14.5v right at the end of the day (on a good sunny day). The batteries seem to struggle at the 13.5v mark for ages (middle of the day), then climb upwards.

    Ideally, you want to see the batteries rise from 12.xx to 14.5 volts (bulk charging, from xx% to 80-90% state of charge) then hold at 14.5 volts for 2-4 hours (rough numbers--80-90% state of charge to near 100% state of charge).... So, if I had to guess, it sounds like you are charging to 80-90% state of charge... 80 is not full charge. Over 90% is full charge. And your bank is not reaching full charge.
    Then at night (7pm), it will settle down down to 12.5v and sort of hang around that. At about 11pm it might be down to 12.3v, then the 12v lights in the house are turned off for beddibyes.
    In the morning it is about 12.2v.

    That all sounds normal. If the bank was "fully charged", the resting voltage would probably be higher.
    But lately (and as now and when things were going bad), the voltage would down to 11.5v in the mornings and then the 12v feed into the house would shut off and then soon after the inverter would start screaming (low v's).

    Sound like sulfating batteries... You can knock years off a battery life by chronic under charging.
    On a good summer day 25c i have seen 450Amps go into the batteries (The highest ever 500). Normal days 300Amps, low/cloudy days 120Amps.

    Sounds like you have a battery monitor? And those are Amp*Hours?
    I admit to making stupid mistakes with my orig T105's. Used a 20amp controller with 4 panels at the start (yes, stupid!), I used car chargers to charge them when they were low. I forgot to top them up with water (could see the plates).
    Now i have many more BP80watt panels! ;) and a 60Amp reg.
    For external Boosting on very bad days i use a regulated 40amp power supply set at 14.4volts.
    And one by they started failing - the charge never seemed to hold as it used to! The battery voltage in the morning was getting lower and lower! Then i found that some batteries were very warm!
    Then it clicked that a lot of solar input was going to them and through the night the other batteries were draining into them!!!
    '

    I have to go now--But I would suggest you get a DC Current Clamp Meter (here is a $60 one that is "good enough" for debugging solar power systems). You can measure the charging/discharging current in each battery string (check for sharing). Open cells will not carry current. Shorted cells may actually show a "-" current flow (charging string) while the rest of the bank is being discharged.
    So now after learning the hard way, i am ready to purchase some more batteries. But i have concerns if the 'final' set up is actually correct and if it is correct to look after the batteries for the long term.

    I'm not sure if i need 12 x 6vs or just go with 12vs. Gel or Wet?
    I guess my most important question is do i have enough amperage input to look after the batteries. Should i use less batteries but get full charge, so it will last longer than having 3/4charge in more batteries?

    I include a very basic picture of my setup. Leads from Reg 2-3mtrs. Leads to INV 2mtrs. Bridging cable for batt series approx 20cm, bridging for batt parallel approx 25cm - so the battery bank is tightly packed with about 10mm air gap.

    http://i202.photobucket.com/albums/aa36/obba41/SolarBatterySetup.jpg

    I get some terminals with the green corrosion 'fungus' growth on some terminals - why do i get that even if they have been cleaned?
    I use terminal cleaner and started to use a terminal protector (put's a brown gunge covering on).
    I use Two Megapulses and have used them to 'stop sulphation'. These are wired across to 6 banks each.

    Sorry for the long post. I found this forum by looking up 6v vs 12v setups and it's clear that this site has a lot of people who know a lot more than i do ;)

    Regards,
    Alan.

    Don't buy any more batteries/hardware until we have more discussions... Type later.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    There's almost no chance that six parallel strings of batteries will share current evenly even if they are wired properly. The batteries themselves will present enough difference in resistance to cause problems.

    You've got 225 Amps hours * 6 = 1350 Amp hours at 12 Volts or over 16 kW hours of power. That is large. If you really need that much stored power, increase your system Voltage to 48 (about 340 Amp hours: one string of eight L16's).

    Wiring: six parallel battery strings should be connected with equal length wires to bus bars, and the inverter and charge controller should go on the same point (common connection point). The "diagonal wiring" is basically for two parallel strings, where you connect up the (+) from one string and the (-) from the other. It keeps the wire lengths (and thus resistance) even.

    Charging: as it is your battery bank needs 135 Amps of charge current. That's two MPPT controllers and about 2100 Watts of array. 60 Amps from the array or 40 Amps from a charger would barely be felt by that battery bank. I bet you saw 450 Watts going to the batteries, not Amps.

    I'd say your next move is to re-evaluate your loads, and then redesign your system. It is way out of balance.
  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Hi Alan,

    I will try this again at home--Borrowed another PC and wiped out my 1/2 done reply (hate control key hits on these new keyboards).

    First, a bunch of reading:

    Deep Cycle Battery FAQ
    www.batteryfaq.org
    All About Inverters
    Choosing an inverter for water pumping
    All About Charge Controllers
    Read this page about power tracking controllers

    Also, if you do not have a Battery Monitor--I highly recommend them. Also, if you have AGM/Sealed batteries, a Battery Monitor (Victron is another good brand) is almost mandatory (since you cannot monitor specific gravity with a hydrometer).
    obba wrote: »
    So now after learning the hard way, i am ready to purchase some more batteries. But i have concerns if the 'final' set up is actually correct and if it is correct to look after the batteries for the long term.

    I don't know anything about your current solar charge controller (but I am not in the business, so that does not mean much).
    I'm not sure if i need 12 x 6vs or just go with 12vs. Gel or Wet?
    I guess my most important question is do i have enough amperage input to look after the batteries. Should i use less batteries but get full charge, so it will last longer than having 3/4charge in more batteries?

    GEL batteries are typically not a good choice for Off Grid solar power... Their maximum charge rate is around C/20 (5%) rate of charge. We like 5% to 13% rule of thumb for rates of charge--with around 10% being nicely balanced. Over 5% charging can cause permanent gas bubbles to form between the plates--In the GEL. Which "ruins" the battery. They are great for UPS systems, just not here.

    AGM are just about the "perfect" Lead Acid battery--Except they cost 2x as much and don't (usually) last as many years in service. AGMs are "clean", don't outgas (except during failures and at end of life). The can supply tremendous surge current and can take quick recharging (although, as always, there are suggested limitations--devil in the details).

    Standard good quality lead acid batteries can last 6-10 years. Forklift batteries can last 15-20+ years (although, should have a couple percent more charging because forklift batteries are a bit less efficient/more self discharge near end of life, and use more distilled water).

    Forklift batteries are available in huge AH ratings (12 volt start at ~500 AH with Crown and go up from there). So it is "easy" to make single string battery banks. But you need a forklift/pallet jack/crane to move batteries (and a smooth concrete surface).

    In general, again a balance system design between load, battery bank, solar panels, and backup genset. Design battery bank for "nominal" loads, healthy solar charge capacity, and plan on using genset during bad weather/unusually heavy loads (when guests visit and want to use hair driers).
    I include a very basic picture of my setup. Leads from Reg 2-3mtrs. Leads to INV 2mtrs. Bridging cable for batt series approx 20cm, bridging for batt parallel approx 25cm - so the battery bank is tightly packed with about 10mm air gap.

    http://i202.photobucket.com/albums/aa36/obba41/SolarBatterySetup.jpg

    Nothing "bad" there--Except I would avoid the large numbers of parallel battery strings for many reasons. A new bank designed with one string would be great--Two or Three strings if no other choice.
    I get some terminals with the green corrosion 'fungus' growth on some terminals - why do i get that even if they have been cleaned?
    I use terminal cleaner and started to use a terminal protector (put's a brown gunge covering on).

    Acid fumes--Typically from charging near full and/or equalization (near 100% full/during equalization, battery bank will generate hydrogen/oxygen gas and "vent" electrolyte mist.

    Keep clean and neutralized (baking soda and water, don't get into cells). And some sort of anti-corrosion grease is a good start.

    There are special caps which "filter out" the acid mist a bit better (and are supposed to reduce water use somewhat): Water Miser Battery Caps (see if they fit your next batteries--And another reason to not have a lot of parallel batteries--use more caps).
    I use Two Megapulses and have used them to 'stop sulphation'. These are wired across to 6 banks each.

    At least one person here found that their (Outback) charge controllers were "confused" by the electrical interference caused by Desulfators and their pulsing. Dramatically reduced the energy harvest by the MPPT Charge Controller.

    It is not really clear if Desulfators work, or just do not hurt. But--for sure--If the battery bank is not "charged correctly", it will not stop or fix sulfation.

    So, a little bit more. As always--the above is personal opinion and guesstimates about your setup. Please feel free to question or point in different directions for solutions that better address your needs/system.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Hi again,
    Time difference here as i'm in Aus and i started the orig post early on the Sat morning.
    Firstly, thank you to everyone for your replies.
    Lots of good advice and some points mentioned is what i was thinking about as my problem.

    So i'll try and break down the replies as they came in...
    BB. wrote: »
    Welcome to the forum Alan,
    From your link below, you are wiring them correctly--But, possibly are falling in the the trap of a massively parallel battery bank... Besides lots of electrical connections and cells to check for water levels--It can be difficult to get batteries to share current properly
    -Bill
    Yes, i see that now.
    BB. wrote: »
    And, believe it or not, the "good connection" (low resistance, everything work well) many times will end up handling 2x or more of a strings "share" of the current--Which can over heat wiring/connections and/or cause a parallel string to cycle more than the rest, and ware out sooner.
    Also--Failures in parallel strings are hard to find. You have an open cell/or open wiring connection that is not passing its share of current--With 5 other strings, how do you know that? Eventually the batteries in that string will self discharge and sulfate.
    Or, you have a shorted cell, which then causes excessive charging current to flow in a string--Overcharging the rest of the cells and possibly discharging the rest of the bank...
    -Bill
    This is what is happening. I'm finding a batt that is warm and when seperated and left to sit is only 4.x volts. Hence has been draining the others...
    BB. wrote: »
    And your bank is not reaching full charge.
    -Bill
    Yes i think so.
    BB. wrote: »
    Sound like sulfating batteries... You can knock years off a battery life by chronic under charging.
    -Bill
    I think is is happening.

    This is the Battery Controller / Regulator. http://www.solaronline.com.au/plasmatronics-pl60-solar-regulator.html

    I am getting 60Amps per hour at peak times of the day.

    I have a clamp meter so i will do some monitoring, i never thought of doing that. But the testing is a moot point now as i am now down to 4 banks with some 2nd hand batteries.

    There's almost no chance that six parallel strings of batteries will share current evenly even if they are wired properly. The batteries themselves will present enough difference in resistance to cause problems.
    I didn't realise that.
    You've got 225 Amps hours * 6 = 1350 Amp hours at 12 Volts or over 16 kW hours of power. That is large.
    Didn't 'work' that out. But i don't think we need that sort of size of backup. We are pretty good for sun here (Gold Coast, Australia). It's a funny thing 'down under' here.

    In the Winter (Apr-Sept), the sun is low and less hours and colder temps, but MANY sunny days. In the Summer (Oct to Mar = Rainy season!), we get more cloud, warmer temps, but when the sun is out we get MASSIVE solar input!! the http://www.solaronline.com.au/plasmatronics-pl60-solar-regulator.html buzzes (cycling to prevent overload i was told), and i have measured 70amp/hr going in. - UV, good for panels, no good for cancer ;)

    increase your system Voltage to 48 (about 340 Amp hours: one string of eight L16's).
    I don't understand that.
    I am thinking as i mention below of going to 24volts - PENDING - If we can keep the 12v feeds into the house.


    Charging: as it is your battery bank needs 135 Amps of charge current. That's two MPPT controllers and about 2100 Watts of array. 60 Amps from the array or 40 Amps from a charger would barely be felt by that battery bank.
    I think this is where my main problem is: The Controller only delivers 60amps / hour. And the 300Amps average per day i mentioned, is the total for the day that it has passed through to the batteries.
    I'd say your next move is to re-evaluate your loads, and then redesign your system.
    Yeah, that's why i'm here. I thought i had done it all correctly as best i could. But i'm seeing how i have to little amps going in for the battery bank - and - too many cables!


    BB. wrote: »
    GEL batteries, AGM, Standard good quality lead acid batteries...
    -Bill
    From what i have read the Trojan T105's seem to be the defacto standard in high quality solar battery designs (Cost/Life.Cycling). However, i don't think i need as many as i will explain later on.

    BB. wrote: »
    Except I would avoid the large numbers of parallel battery strings for many reasons. A new bank designed with one string would be great--Two or Three strings if no other choice.
    -Bill
    How could i make it ONE string? Or cut down the Strings with my current design?
    BB. wrote: »
    Acid fumes--Typically from charging near full and/or equalization (near 100% full/during equalization, battery bank will generate hydrogen/oxygen gas and "vent" electrolyte mist.
    -Bill
    I hear the batteries in the middle of the day bubbling and a soft kick will create more bubbling. As i stated the cables are short and the batts have about one inch gaps. At least i know that it's not (Green fungus), due to bad cleaning etc.
    BB. wrote: »
    It is not really clear if Desulfators work, or just do not hurt. But--for sure--If the battery bank is not "charged correctly", it will not stop or fix sulfation
    -Bill
    I am led to believe that sulphation only occurs when there is no charge going to the lead plates. So i bought them to 'prevent sulphation' to the batts through the night time....


    OK, here is where i am at after reading all your helpful comments:

    1) I have a large multi string battery setup = Not recommended.
    2) I don't have enough AMPS through the day to charge my current battery bank = Not recommended.

    We don't need a massive back up. We live in an urban area and it all started as a back shed light setup and grew from there... Much to the missus's dismay.

    The only time she was happy about it, was when the street had a blackout when we were having a BBQ with visitors and the house stayed lit and the music and a TV were still running - after most of the normal kids tv's shut off - she smiled and said "Oh, didn't i mentioned we have solar backup...". That was my moment of glory ;)


    Options:
    Seriously! Money is an issue. It's been trouble and now at a head.

    It's clear i have to reduce either the cabling, or reduce the qty of batts by going 12v batts instead 6v batts.

    1) I either lower the number of batteries to cater for the 300amps (avg), per day.

    2) I goto a 24volt invertor and still reduce the qty of batts and cabling - which - might be even better to go 12v batts and not the 6v batts....

    Which ever way i go, i have to REALLY CONVINCE HER that it 'isn't going to happen again'.

    I can source (via a friend), T105's for AUS $200ea.

    A 24v invertor http://www.ebay.com.au/itm/MAX-4000-WATT-2000W-24-VOLT-240-VOLT-REAL-PURE-SINE-WAVE-POWER-INVERTER-/280918562042?pt=AU_Car_Parts_Accessories&hash=item41680d14fa

    However, at the time writing this, i don't know if the Plasmatronics PL60 still allows the 12v feeds out, if the input from the panels is 24V. I'm dead if the 12volt lighting in the house is not usable anymore and don't dare mention 24 to 12 convertors.... please...


    When Cariboocoot is saying my current battery bank is 16 kW hours of power: Is that what the batts can give out in a normal duty cycle per day (assuming correct solar input), and last for 6-7 years?

    I think i would be happy to have 10 kW hours as a back up.

    So if a light globe is 100W and on for 10hours is that 1kW usage andif we have a 10 kW battery bank the light can stay on for 100 hours with no recharging - that formula goes with that?

    If i went to 12volt Trojan batteries and to keep the strings down and have 10kW, staying with our current 12/240 invertor. What model of Trojan would you guys advise?

    Or if i went to a 24volt Invertor (Would need to change the solar panels wiring), should i then stay at the 6v T105's for the kW (but that's lots of cabling isn't it!!)?

    OK. Have to go.

    Once again thanks for the advice and i look forward to reading the followups in the morning.

    Alan.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Here's a thread about battery system Voltages and their equivalent power: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
    I suggested 48 Volt system if you really need all that stored power. You probably don't. You probably don't need 10kW hours worth either. Most off-grid systems are under 5kW hours. I use less than 3kW hours daily.

    The loads is the first thing to get a handle on. That determines what everything else should be. Trying to do it otherwise ... gets you into a mess.
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    Here's a thread about battery system Voltages and their equivalent power: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power
    I suggested 48 Volt system if you really need all that stored power. You probably don't. You probably don't need 10kW hours worth either.
    .
    I think you are correct. I'm looking at 24V at the moment. Just need to check that the PL60 still has the 12volt feed out.
    Most off-grid systems are under 5kW hours. I use less than 3kW hours daily.
    Ok.

    The loads is the first thing to get a handle on. That determines what everything else should be. Trying to do it otherwise ... gets you into a mess.
    I've found some energy meters that show how many watts are being called on. Installed them yesterday. I'll reset them both and see what the totals are over a week.


    With my dying batteries, i noticed that they died from the bottom upwards (as per my drawing). Why would they do that?

    I'm down to 4 banks now (all second hand), from my original 6 banks of brand new T105's .


    Also i managed to measure the AMPS with a Clamp Meter - and you and everyone is corret, again! The amps on the side cables (Parallel cables), were showing different currents as i checked up and down each bank - With a 50Amp charge showing on the PL6, i was measuring 36A, 15A, 10A, 22A and so on, all fluctuating. The series cables also showed different.
    Clearly (if i'm right), an unbalanced system!

    How are your batteries cabled up?
    I saw this system somewhere, what do you think? I can't work out where the feed to the Inverter would go though...
    http://i202.photobucket.com/albums/aa36/obba41/DiffSolarCabling.jpg


    Say i want to go 5kW Hours, 24V, what type of batteries would you go for 6v or 12v?

    EDIT: I'm reading that link BTW ;) Where can see in a drawing those different wiring setups mentioned?

    Many thanks.
    Alan.
  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    obba wrote: »
    With my dying batteries, i noticed that they died from the bottom upwards (as per my drawing). Why would they do that?
    From an engineering point of view--It could be random chance or it could be one side of the bank gets hotter than the other (sunlight, poor ventilation, etc.).
    Also i managed to measure the AMPS with a Clamp Meter - and you and everyone is correct, again! The amps on the side cables (Parallel cables), were showing different currents as i checked up and down each bank - With a 50Amp charge showing on the PL6, i was measuring 36A, 15A, 10A, 22A and so on, all fluctuating. The series cables also showed different.
    Clearly (if i'm right), an unbalanced system!

    There are lots of possible reasons for string current imbalance...
    • Poor electrical connection(s)--clean and re-torque hardware.
    • Bad wiring (corrosion inside cable).
    • Different wiring (longer cable adds more resistance)
    • Battery Cell issues (shorted/undercharged cell draw more current by keeping cell voltage "low". High resitance cells--bad/sulfated/not enough water/etc.--Raise cell voltage and reduce current
    • Even battery temperature differences can affect current flow... Hot batteries charge at a lower voltage--So batteries that are hot because they are already carrying more current during charging/discharging, will run a slightly lower voltage and pull more current.

    All of the above are reasons why lots of parallel connected strings of lead acid batteries are difficult to manage properly for long life/optimum performance. In many cases, one "fault" (whatever it is), causes one string to fail to load/charge correctly--it stops "sharing" the work, and the rest now are cycling deeper than you expected.... And the one faulted string may fail early from under charging (open cell/connection) or over charge (shorted cell/running hot).

    One engineering solution is to actually add resistance to each string (several foot longer cable/adding a fuse or breaker per string, etc.). The battery may have 0.010 ohms of resistance... And if your cables are less than 0.010 ohms, then the batteries will "direct" current flow.

    If you make the cable resistance per string 0.020 ohms--Then they act like "ballast" resistors and the (hopefully) stable resistance of the cables will force sharing even when the batteries are less than ideally matched.
    How are your batteries cabled up?
    I saw this system somewhere, what do you think? I can't work out where the feed to the Inverter would go though...
    http://i202.photobucket.com/albums/aa36/obba41/DiffSolarCabling.jpg

    That is a perfectly OK method of connection too. Again, each string should have its own fuse/breaker to reduce the chance of a short being fed current from the rest of the parallel connections.
    Say i want to go 5kW Hours, 24V, what type of batteries should i be looking at 6v's or 12v's.

    My first suggestion is to define what your bank needs to "look like"... So, using standard rules of thumbs of 1-3 days of "no sun" and 50% maximum discharge (pick 2 days for this example as "nominal" balanced bank design) and 85% efficient inverters:
    • 5,000 WH per day * 1/0.85 inverter eff * 1/24 volt bank * 2 days no sun * 1/0.50 max discharge = 980 AH battery bank

    The batteries I would pick, ideal would be 980 AH cells... And a question for you--Can you use a forklift/crane to move a heavy 12 or 24 volt battery around, or should you get 4 volt or 2 volt cells instead.

    Just some examples from this hemisphere:


    So, it is possible to design a battery bank with only one series string of batteries in very high AH ratings...

    But, at 980 AH @ 24 volts--That makes a 10% rate of charge to be ~98 Amps... You would need 2x Solar charge controller to manage that large of an array... If 48 volts, then the nominal charging current would be 1/2 or ~49 volts--Only one Solar Charge controller needed.

    Anyway, a different way of answering your questions... Comments?

    -Bill

    Here is one website that discusses the details of paralleling battery banks--But you already know 2 of the 3 common methods:

    http://www.smartgauge.co.uk/batt_con.html
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 32,008 admin
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    I should also add, use your digital volt meter set to 2 volt or 200 mV full scale and measure voltage drops at all of the connections--It is a quick way of finding "open/poor" connections (note that voltage drop testing only gives usable readings when there is "high" charging or discharging current flowing. With no current flow, you have no voltage drop).

    Also, measure the voltage across each cell/battery... You may find some high/low readings that need to be investigated. (Resting voltage shows approximate state of charge--Use a hydrometer to measure actual state of charge for each cell and see what is happening).

    And you may see variations in current as the "balance" each other out--Looking for long term averages--not second by second which will drive you nuts.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    obba wrote: »
    .
    I've found some energy meters that show how many watts are being called on. Installed them yesterday. I'll reset them both and see what the totals are over a week.

    Good. This information is vital!
    With my dying batteries, i noticed that they died from the bottom upwards (as per my drawing). Why would they do that?

    The random chance of varying resistance causing a "ladder" effect in which the "bottom" batteries got the most current drawn and the least replaced.
    Also i managed to measure the AMPS with a Clamp Meter - and you and everyone is corret, again! The amps on the side cables (Parallel cables), were showing different currents as i checked up and down each bank - With a 50Amp charge showing on the PL6, i was measuring 36A, 15A, 10A, 22A and so on, all fluctuating. The series cables also showed different.
    Clearly (if i'm right), an unbalanced system!

    This is pretty much what we'd expect. It's why several parallel batteries is so much trouble.
    How are your batteries cabled up?

    Easy: I only have one string. :D

    [QUOTE}I saw this system somewhere, what do you think? I can't work out where the feed to the Inverter would go though...
    http://i202.photobucket.com/albums/aa36/obba41/DiffSolarCabling.jpg[/QUOTE]

    Smart Gauge battery wiring diagrams: http://www.smartgauge.co.uk/batt_con.html
    Method #1 is always the wrong way to do it.
    Method #2 works best with only two parallel strings.
    Method #3 is the plan for more than two parallel strings.
    Method #4 is too confusing for most people to deal with. :p

    Say i want to go 5kW Hours, 24V, what type of batteries would you go for 6v or 12v?

    Usually you can get higher Amp hour capacity with lower Voltage batteries. Since it is best to store power at higher Voltage with as few parallel connections as possible, you usually buy 6 Volt high Amp hour batteries and put them in series to get the right Voltage for the system. 5kW hours is roughly 210 Amp hours on 24 Volts; a minimum of 420 Amp hour battery bank (50% DOD). Ordinary golf cart type batteries (220 Amp hour) can supply this as two parallel strings of four. If you want lower DOD you should consider bigger batteries like the L16's or even forklift batteries (monolithic monsters, but they have got power). Peruse NAWS deep cycle battery offerings to get some idea of what's available: http://www.solar-electric.com/batteries.html
    EDIT: I'm reading that link BTW ;) Where can see in a drawing those different wiring setups mentioned?

    What? You want pictures too? :p
    I don't even have my "real" computer so I'm stumbling around as it is. How do people put up with Windows? :confused:
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Ok.
    Firstly, once again, i would like to thank everyone for your advise and guidence.

    I'm not going to post the quotes of the replies - as i'm getting confused.
    So i'll be saying where i am at now with my conclusions...

    Note: It's a money game. And as in other things in life, the more you spend the better it is... We just don't have the money at this time, and probably we don't have the income to go further - BB quoted a (single), forklift 12v battery at $2,500... We can't do that sort of stuff.

    Funny thing is that the link provided by Cariboocoot about the wiring string setup is the one that i remembered seeing.. ;) Just couldn't remember where i had seen it. The missus is getting sick of my on line browsing :(

    Back to basics: I'm sticking with 12v.
    Why? Just not comfortable with having 24v in the shed. Have some 12v lights in there and it's good for me to play around with car stuff and the thousands of things that run off 12v. Plus it means a new inverter $500+.
    All the panels on the roof are wired up. My missus hates me going back on the. I've forgotten the amount of times i've said "last time..."



    I've done some calculations on my usage. Two energy meters (I have 2 x 240volt feeds into the house), across two days.

    80W for 24hours = 1920W per day.
    200W for approx 6 hours = 1200W per day.
    100W for approx 6 hours = 600W per day.


    The PL60 has a 12volt output. I have 3x 12v feeds into the house, that power 12v CFL lights. I cannot measure this of course via the power meters. Yes it has a 12v Amp total but i have had to take an average of when these lights are used over time, not on a daily basis.

    12V only: 10qty x 13W CFL's X 6 hours = 720W - i have no idea if Watts @ 240v is the same as Watts @ 12volts.


    I'm look at halfing my capacity and cutting down on cable connections by getting 6 QTy of these batteries. And the PL60 Reg should be ok to handle this correctly.

    Batts 105 amp hours x 6qty = 630 Amp hours: @ 12volts = 7.56kW hours of power. (Is that right?)


    So is the house using ;

    1920W
    1200W
    600W
    720W (12volt)

    Total per day 4.440kW ?

    Is this 'amperage' ok for the reply from BB ok for what i am doing...;
    BB. wrote: »
    So, using standard rules of thumbs of 1-3 days of "no sun" and 50% maximum discharge (pick 2 days for this example as "nominal" balanced bank design) and 85% efficient inverters:
    •5,000 WH per day * 1/0.85 inverter eff * 1/24 volt bank * 2 days no sun * 1/0.50 max discharge = 980 AH battery bank
    -Bill
    Or does the 24v vs 12v amps/PH etc make me an idiot?


    The new batteries i am looking at are 6 qty Trojan 12volts rated to 105Amps

    Model 27TMX
    Minutes:
    175 @ 25Amps
    45 @ 75Amps

    Amp-Hours:
    85 @ 5 Hr Rate
    105 @ 20 Hr Rate


    With the cabling 'method', i'm going to go with method #2 as the Smartgauge site.

    But as he says at the end, "Where do the charging cables go..."? And the answer is as they say 'The Bleed'in obvious'.
    I'm concerned as to how the Inverter is going to handle the 'incoming current' off the panels as they are connected to same incoming voltage/current off the battery bank - before - the incoming current has had chance to charge the batteries. Isn't the incoming voltage and current different to the voltage and current off 'a' battery bank?


    As for resistance in the joining cables: I got out my super duper multi meter and measured on some spare 15cm to 25cm cables crimp to crimp 0.2Ohms and when sticking the probes into fresh copper (snicked out a bit of the insulation close to the ends), i was getting 1.7Ohms. Is that bad?


    Ok. Got to go: 7:00pm here. Getting the 'calling....'. ;)

    Regards,
    Alan.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    "Batts 105 amp hours x 6qty = 630 Amp hours: @ 12volts = 7.56kW hours of power. (Is that right?)"

    That's the total power, not the usable power. At 50% DOD you have 315 Amp hours * 12 Volts or 3780 Watt hours DC. The AC will be less because you have to feed the inverter and allow for conversion inefficiency.

    You will have trouble with six 12 Volt batteries in parallel. Really, four is the limit. It starts to get crazy trying to keep them even above that. If I were you I'd get some higher Amp hour 6 Volt batteries and make strings of two. The problem is that with your desired daily power requirement you're looking at approximately 800 Amp hours @ 12 VDC. That is a lot of big, expensive batteries. If you up the system Voltage to 24 it drops to 400 Amp hours, and that can be supplied with two parallel strings of four 'golf cart' type batteries (220 Amp hours @ 6 Volts).

    "I'm concerned as to how the Inverter is going to handle the 'incoming current' off the panels as they are connected to same incoming voltage/current off the battery bank - before - the incoming current has had chance to charge the batteries. Isn't the incoming voltage and current different to the voltage and current off 'a' battery bank?"

    This is not an issue. Trust me. Electricity takes the path of least resistance, but not the "first fork in the road" it comes to.

    Funny, but my missus is always telling me to get back up on the roof - and finish it. :p
  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    obba wrote: »
    Hi all,
    All DIY and this is my first post asking for professional help, due to the cost involved in buying new batteries. All my work has been from what i have read from the net - and i've been told many conflicting stories.

    Info overload here i'm afraid :) Just feel i have to say it in one go and try not to miss something obvious to you guys.

    So as i stand my original 12xTrojan T105's (6 Banks of 12v), have all died within 4 years and i've got some 2nd hand ones dying now.

    Alan.

    Look at the difference in specification between the Trojan T105 and the Trojan T105RE. The latter is a true deep-cycle battery (with more lead and a different plate geometry) and will handle many more discharge cycles, for a modest increase in price.
    SMA SB 3000, old BP panels.
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Thank you for that info.

    The suppliers i was talking to do a T105+ so will have to check if that's an RE.

    Another supplier had ordered the RE's but when the stock was due to arrive, they were told that there wasn't enough demand and that (their supplier), was only going to supply the normal 105's.
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Hi all,
    Did some more research. If we go 24volt;

    The PL60 will give out 12v, 24v (or 36v, 48v), on the DC load outlets depending on the battery bank voltage. I have 3 feeds off this into the house that every room in the house has native 12v lights. Obviously these can be changed (and may have to do be the fittings), to 24v.

    I can purchase a 24v to 12v 20A output convertor (Can't locate a 30A output one), approx $100 and a few more bus connections.
    A new 24v to 240v convertor will also be needed $500+

    I spoke to someone yesterday who has a PL60 and has 8 T105's at 24v and i have a feeling (from his talkings he is an old guy and i couldn't make out a lot of what he was saying), he has wired his 8 batts up like Method 4 as in http://www.smartgauge.co.uk/batt_con.html but on 8 batteries.

    He mentioned two strings (somewhere!), and i admit i'm still having trouble knowing what 'a' string is. Is method 4 two strings or one string?

    As i'm also looking at 8 (at 24v) and 6qty (at 12v), T105's i have to try and adapt Method 4 to 8 batts;
    """Even with 8 batteries it is possible to get reasonable balancing by placing the main "take off" feeds from somewhere down the chain instead of from the end batteries. Remember, count the number of links each battery needs to run through to reach the final loads and get these as equal as possible."""

    So what do you all think of that. I'll need help to know how to wire up 8 batts (24v), as in method 4.

    As a last resort if we stayed at 12v (and 8 T105's), I'd need help with cabling up method 4 as well.


    The missus is really not happy with purchasing any modifications to 24v.
    I can't fault her logic as we have everything in place and only need to get 6 or 8 batts as we had to many before (12qty), and if they are cabled differently so as to be more equalised. Just the cost in extra cable, crimp lugs etc is going to be in the $ hundreds.

    Is anyone able to draw up a suitable cable pattern for 6 qty T105's at 12v? and 8 qty T105's at 24v.

    I think the PL60 can charge 6 T105's at 12v (3 x 225Ah) and so will provide 4050 Watt hours at 50% DOD -- Am i right in that?


    Many thanks and we do really appreciate your time and advice.
    Regards,
    Alan.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    There's only one way to wire eight T105's for 24 Volt: two parallel strings of four.

    A 'string' in this context is two or more batteries in series (positive to negative) to increase the Voltage. In this case:

    (-) BATT (+)---(-) BATT (+)---(-) BATT (+)---(-) BATT (+)

    The string then essentially becomes one '24 Volt' battery. Connect the end negatives and end positives of two such strings for the parallel connection. Do not make connections between the individual batteries in the two strings, as this creates alternate current pathways and defeats the whole purpose.

    You can expand on this drawing by adding one more string to get three parallel strings of two T105's in series for 12 volts.

    Attachment not found.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Forgot the math:

    three strings of 225 Amp hours = 675 Amp hours @ 12 Volts. 50% DOD is 337.5 Amp hours * 12 Volts is indeed 4050 Watt hours DC. You will lose some of that potential to running the inverter and converting to AC. Also not a good idea to go below that, but if that's your maximum DOD it's good.

    Recharging should be about 67 Amps, which is not much of a problem. Most controllers only handle 60 Amps. So at maximum current (and the deeper the discharge the more likely you are to see that) you'll have a charge rate of about 8%.

    In terms of panels this should require approximately: 60 Amps * 12 Volts = 720 Watts / 0.77 = 935 Watts.
    Note that an array that size will only produce about 2.4 kW hours AC on a good day. That's a bit more than half what the batteries can supply.

    Some of your loads are DC, which may make the system a bit more efficient. On the whole I'd say it has potential, but not quite the balance it should have.
    Get the "fudge factors"* to work in your favour and you'll be all right.

    *Got to list those somewhere some day:
    1). Round loads up; always assume you'll use more than you calculated for.
    2). Round battery Amp hours available down for supplying loads; they will lose capacity over time.
    3). Keep charge current potential high, as loads will draw while charging reducing the net rate.
    4). Round array size up, as not every day is sunny and the ones that are usually are also hot (lowers panel output).
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    24 V to 12 V DC-DC converter, up to 70 amps.

    http://www.victronenergy.com/dc-dc-converters/orion-dc-dc-converters-12v-24v-48v-96v/
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Ok.
    24volt it is!
    The missus has given in... But! If "You keep running into problems again and it doesn't work as they say - it's not their money - then no more faffing around with this, ok!".
    So that's where i am now.

    Thanks to Blackcherry04 and his link. I can source in QLD that brand 24vDC to 21vDC 40Amp for approx $180.

    Cariboocoot, i can't thank you enough. I hope you have the persiverance to stay with me till it's done ;)

    On the house roof (northish), i have four banks of panels and four cables coming in to the back shed that get joined on two buses (NEG and POS). So it isn't going to be hard to wire them to 24volts. However, i have some panls facing Westish, this allows a nice spread after mid day and into the night.

    On HIGH UV Sunny day i have seen the PL60 read over 70amps - and then you can hear is 'buzzing', as it regulates the amps back to 60. So i set up another 20amp reg that i can manualy switch the West facing bank over, assuming that they were generating the extra 10amp input.

    Question 1) If i go 24v will i see 30amps on the PL60? (As i see 60amps on 12volts). Therefore, i don't have to switch anything over with the West bank of panels.

    Question 2) If i go 24v x 8 T105's, will the PL60 charge them ok?


    As for cabling, i found this; http://www.ebay.com.au/itm/251105080355?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
    The seller has a range of different lengths - 4 Gauge - and different lenghts in the kits he sells.

    Question 3) Will these pre-made cables be thick enough and ok to equalise the batterys?
    I don't mind buying various 'kits', to get the cables pre-made.

    What about this 24-240v invertor ? http://www.ebay.com.au/itm/320605904293?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
    The seller has a fair range and 100% Feedback.

    One of my convincing arguments going to a 24v 2000W PSW invertor was the ability to maybe run two fridges (when we tried that on 1000W), both fridges cut in about the same time! Dropped out. Of course the startup current is the main issue.


    Whew! Ok. have to go.
    Look forward to your replies....

    Regards,
    Alan.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    obba wrote: »
    Cariboocoot, i can't thank you enough. I hope you have the persiverance to stay with me till it's done ;)

    This would be the third system in Australia I've helped with. :D
    On the house roof (northish), i have four banks of panels and four cables coming in to the back shed that get joined on two buses (NEG and POS). So it isn't going to be hard to wire them to 24volts. However, i have some panls facing Westish, this allows a nice spread after mid day and into the night.

    I'm not familiar with your controller. Just note that if it is of the MPPT type it won't give the best output with panels facing in different directions.
    On HIGH UV Sunny day i have seen the PL60 read over 70amps - and then you can hear is 'buzzing', as it regulates the amps back to 60. So i set up another 20amp reg that i can manualy switch the West facing bank over, assuming that they were generating the extra 10amp input.

    Question 1) If i go 24v will i see 30amps on the PL60? (As i see 60amps on 12volts). Therefore, i don't have to switch anything over with the West bank of panels.

    Approximately, yes; as you increase the system Voltage you decrease the Amperage for the same amount of power in Watts. That 70 Amp peak would show up as about 35, perhaps a bit more (more efficient conversion on 24 Volts, less loss in wiring).
    Question 2) If i go 24v x 8 T105's, will the PL60 charge them ok?

    Eight T105's is 450 Amp hours. 30 to 35 Amps peak Voltage would be 6% to 7% charge rate. This is a bit low, especially with loads drawing while charging. However, the system may produce more peak current than you expect due to the increased efficiency. If the batteries are not deeply discharged it will help.

    As for cabling, i found this; http://www.ebay.com.au/itm/251105080355?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
    The seller has a range of different lengths - 4 Gauge - and different lenghts in the kits he sells.

    Don't buy any wire until you've planned the whole thing out. You need to know how much current is expected. 4 AWG is good for up to 100 Amps tops. Best below, say, 75 continuous. At that current 24 Volts will deliver 1800 Watts. 2 AWG will give you a big advantage over 4 AWG.
    Question 3) Will these pre-made cables be thick enough and ok to equalise the batterys?
    I don't mind buying various 'kits', to get the cables pre-made.

    Equalizing does not require high current. It is higher than normal charging Voltage, done when the batteries are fully charged. Wire gauge is not an issue here.
    What about this 24-240v invertor ? http://www.ebay.com.au/itm/320605904293?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
    The seller has a fair range and 100% Feedback.

    It has no built-in charger. Judging by the case size/design I'd say there is no way it can handle its rated output for very long. These "no name" inverters tend towards disappointment in my experience. That said, I have no actual experience with the particular product in question.
    One of my convincing arguments going to a 24v 2000W PSW invertor was the ability to maybe run two fridges (when we tried that on 1000W), both fridges cut in about the same time! Dropped out. Of course the startup current is the main issue.

    Here is where the cheap inverter will fail you. I did not see any info on how long it could sustain that 2X peak power output. This looks similar to the small Samlex/Cotek inverters, and their surge rating is so ridiculously short as to be non-existent.

    If you're making the investment for the long-term, go for quality equipment. It too is not always perfect but the odds are in its favour, and companies like Morningstar, Exceltech, Outback, MidNite, et cetera have excellent customer service (not Xantrex/Schneider, however). How good is the service from a brand that doesn't have a name?
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Hi Cariboocoot,

    Great advice there.

    I didn't think about having to charge/boost it with a 24v charger - incorporated with the invertor.
    Will check some out today if i get time.

    Those premade buggy cables look good for equalising, but i wont buy anything unitl i get the system up and running.

    I'll do some hunting for a invertor / booster.

    Cheers,
    Alan.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    It occurs to me we may be talking at cross purposes here.

    "Equalization" is a charging process where battery Voltage is raised above normal to bring the specific gravity of cells in line with one another; equal. Wire gauge does not matter here; if it's large enough to handle the high current of the Bulk stage it will be fine for the rest.

    I think you may be thinking of the benefit of pre-made cables of the same length being used to connect batteries so that the current is shared equally between two (or more) parallel connections. In this case it is essential that all parallel cables be the same gauge and length; equal.

    I hope that clears that up. :D
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    It occurs to me we may be talking at cross purposes here.

    "Equalization" is a charging process where battery Voltage is raised above normal to bring the specific gravity of cells in line with one another; equal. Wire gauge does not matter here; if it's large enough to handle the high current of the Bulk stage it will be fine for the rest.

    Yeah that's ok. I understand the difference. That little much i know.... ;)

    I think you may be thinking of the benefit of pre-made cables of the same length being used to connect batteries so that the current is shared equally between two (or more) parallel connections. In this case it is essential that all parallel cables be the same gauge and length; equal.

    I hope that clears that up. :D

    I was thinking of using my existing 'thick' cables and using those others to 'equalise' the 'rest'.


    As for the Controller and Charger with some of the brands you have mentioned is now a big problem with the price. There isn't any way we can afford those sorts of prices. Of course i am guilty - as the question of the guy bying a Rolls Royce: If you have to ask how much,, etc.

    Just thinking about the 12v to 24v conversion and how the panels are wired up on the roof. Will do anotherbasic diagram as to what i mean...

    Have a good night guys..

    Cheers.
    Alan.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    there is another way to supply your 12 v loads, if they are low enough, and that is to get a reasonably priced 12V pwm charge controller and have it charge 1 -12 v battery, that may keep SWMBO happy in the switch over to all 24v...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Hi all,
    Been away for a bit. And we have saved some money to go ahead with the 24volt setup.

    I have ordered 8 T105's RE's.

    And i just wanted to know how i have to change the cabling system to get 24v into the PL60 regulator.

    This is the roof setup:
    http://i202.photobucket.com/albums/aa36/obba41/Currentsystem_zps207a3b65.jpg

    There are 5 panels (in a bank), and wired to be give out 12v.
    There are 4 banks (sending 4 feeds of 12volts to the regulator).
    There is approx a 4-6mtr run to the edge of the roof. And then a further 7-8mtr run to the Regulator. These runs are one continuous cable.

    So a real stupid question, but i have to ask:
    As a bank of panels is giving out 12v, is it ok to make two (out of the four feeds), to join two of them in series (giving 24volts) at the input of the bus bars?

    So in effect i will make the 4 feeds join into two 24v feeds at the bus bars [Nice easy way as to not have change any cabling across the roof].

    Or this will negate the 24v (less cable thickness advantage), run from the solar banks?

    If so, what about (at the 4-6mtr), joining the 4 x 12volt banks into 2 feeds of 24v at the roof level [Will require a cable box enclosure] and then the remaining 7-8mtr run is all 24volts...?


    Thanks...
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    the simplest way to describe this is to hook the negative of panel #1 to the positive of panel 2 and the pos of panel 1 and the neg of anel 2 to the buss bar. Hope this makes sense. try drawing it out.
    In this way the voltage will be 12 + 12 = 24 from 2 panels.

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    You are now going with a 24 Volt system, correct?
    You will need an array capable of at least 35 Vmp. Having the panels wired as 12 Volts won't even nudge the battery, much less charge it.

    Normally you get panels and they have polarized MC4 connectors on them. Plug two together and you get a series string of two panels that produces 24 Volts nominal.
    Put four in series by this manner and you get a nominal 48 Volt string. Parallel five such strings together and feed it to an MPPT type charge controller. There's your twenty panels used. The output will be fine for charging a 24 Volt system.

    And did anyone mention the need for fuses/breakers on each string?
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    westbranch wrote: »
    the simplest way to describe this is to hook the negative of panel #1 to the positive of panel 2 and the pos of panel 1 and the neg of anel 2 to the buss bar. Hope this makes sense. try drawing it out.
    In this way the voltage will be 12 + 12 = 24 from 2 panels.

    hth

    Thank you for that advise! Very simple and i get it straight away.

    Cheers,
    Alan.
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    You are now going with a 24 Volt system, correct?
    You will need an array capable of at least 35 Vmp. Having the panels wired as 12 Volts won't even nudge the battery, much less charge it.

    * Hi Cariboocoot (glad to see your still here), yes starting to go 24v.

    * With this "array capable of 35vmp and the panesl wired as 12volts.." What is this 35vmp?


    Normally you get panels and they have polarized MC4 connectors on them. Plug two together and you get a series string of two panels that produces 24 Volts nominal.
    Put four in series by this manner and you get a nominal 48 Volt string. Parallel five such strings together and feed it to an MPPT type charge controller. There's your twenty panels used. The output will be fine for charging a 24 Volt system.

    * The 'big panels' i have are 5 a piece, not 5 'big panels' by 4 individual solar panels...
    * We don't have the money to buy a MPPT type charge controller. I have read about the MPPT controllers and whilst they can 'distribute' the panel(s), * maximum input to the batteries etc, it IMO and in our case, is not cost effective.

    And did anyone mention the need for fuses/breakers on each string?

    * Yes, i will be looking at that. At the moment, I have a fuse/breaker on the input - after the bus bars - to the PL60 and then the same after the PL60.
    * So i will once i get the wiring to 24volts, have a fuse/breaker on the 'new' two feeds.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: About to buy new Batteries - not sure if my set up is correct to start with
    obba wrote: »
    * Yes, i will be looking at that. At the moment, I have a fuse/breaker on the input - after the bus bars - to the PL60 and then the same after the PL60.
    * So i will once i get the wiring to 24volts, have a fuse/breaker on the 'new' two feeds.

    Two feeds? According to my calculations you will have five feeds to the combiner and that means five fuses or breakers; one on each string.
    You must not combine strings and then connect to circuit protection. It will not be safe for the reasons we use circuit protection there.
  • obbaobba Registered Users Posts: 14
    Re: About to buy new Batteries - not sure if my set up is correct to start with

    Batteries have arrived and i have put them in (12volt) for now, until we organise the 24v Inverter.

    What are your views on these MegaPulses?

    http://www.megapulse.net/testimonials.html


    I have got two Megapulses MKIII's

    I was going to attach them to the battery banks, One Megapulse to 4 batteries the second megapulse to the second 4.

    Snake oil, or they do work?
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