New to this site

Jeff G. · November 2009

Hi Everyone,
I have lurked for about a month and this looks like a wonderful site. I am new here and pretty new to solar as well. My off grid system currently consists of 4 Mitsubishi 185 watt 24v solar panels, 24 marathon mv6 batteries 6 strings of 4 at 190amp hours per string, magnum ms4024AE inverter prebuilt midnight solar e panel, morningstar 60amp ts-60 charge controller. A Watsun/array technologies tracker mounted on a monopole. I with a couple of friends installed this system in August of 2008 (at that time I had 6 older 50 watt 12v panels (probably putting out about 40 watts each). The system was flawless until sept 2009 when we used the system very hard for 4 days dragging the battery bank to 22v causing it to shut down (the system was set to shut down if 22v was reached). I then let it recharge for 2 weeks but it never really came all the way back and the high voltage in the system was about 24.5 volts. I since changed the panels and my battery bank voltage after recharging has edged up to 25.5volts. In the first year it would normally hit about 27v.
I know that I got into this without any training and little knowledge so you all may see all kinds of errors in my setup. I think I may have beat up the batteries and now they are not working as well as before. I am planning a system shutdown, disconnect all batteries and test for weak batteries. I am also getting the morningstar charger meter so that I can get some additional data. I recently purchased 24 170amphr at 12v battery corp new batteries (133lbs each) and 18 norstar 100amphr at 12v that are not in use. I am planning a second bank charging off my old panels setup in a fixed panel. I will have to figure out how to post photos here.
Thanks, Jeff G.

BB. · November 2009

Re: New to this site

Sounds like there is something wrong in your charging circuit (wiring, connection, controller, etc.). A second problem could be a shorted cell in a battery dragging down the whole string.

So--tools. Get a decent DVM. Measure voltages at various points in your system and record them. For example, your PV panel Inputs should be Vbatt+1-2 volts or so (if the controller is working hard to charge your battery bank). If Vpanel input is high--then the controller is not pulling the current for some reason.

I like to take a DVM and set it down to 2 volt or even 200 mVolt scale and measure voltage drops across lengths of wire and connections. For example, if you have 2' of wire to each battery string--check the voltage drop on each wire under load and/or when charging. If the batteries are sharing current, then each wire's voltage drop should be similar. If one wire has near zero voltage drop while the others show drop--then that string may have a bad connection/or open cell. If you show one string with a large voltage drop, and the others with smaller drops (during charging), then that bank may have a shorted cell--etc....

For flooded cell batteries, using an accurate hydrometer once in a while (or when having problems) can isolate if the problem affects all batteries, or just one string. or even just one battery.

For long term use--I would highly recommend a Battery Monitor of some sort. Running an battery bank without one is almost like running your car without a gas gauge.... Can be done, but mistakes will happen. A battery monitor can pay for itself with the first battery bank that did not die an early death.

Normally, even if the batteries are going bad (unless there is the rare shorted cell)--you would not see low battery charging voltage as a symptom of bad batteries. I would guess this is a symptom of a bad charging circuit (somewhere). Even old batteries will go up to peak charging voltage pretty quickly (faster than newer/good batteries).

In the end, get the batteries charged >75% state of charge (at least to 90% using a generator if you have too; so they don't don't sulfate/die sooner) and look at the major sections of your system for obvious faults.

If you can justify the money, a DC current clamp meter would be helpful too (although--I would probably spend the limited funds on a Battery Monitor first, as my choice).

-Bill

Jeff G. · November 2009

Re: New to this site

Hi Bill
Thanks for your thoughtful response. Is a DVM a DC volt meter?
I don't think it is bad wiring as it was working fine until the fateful day unless we burned out a wire somehow. It certainly could be a bad battery or string.
I will invest in a battery monitor, I noticed that the Xantrex can take 2 battery inputs which may make sense for me as I expect to have 2 battery banks soon or maybe 2 seperate meters would be better. I followed your link, do you recommend a manufacturer of the battery monitor?
My batteries are AGM sealed so I can't check them with a hydrometer.
I can borrow a DC clamp meter for other testing.

Being a mechanical not a electrical guy I will have to walk slow, my good friend who was my electronics guru passed suddenly this year at a very young age. I miss him in many ways he was my sons godfather, my hunting and scuba partner and heck my electronics guy and close family friend, ahhh but life goes on. I appreciate your help.
Jeff

BB. · November 2009

Re: New to this site

Jeff,

DVM=Digital Volt Meter
DMM=Digital Mutli-Meter (really what I should have typed)

Just get a decent digital multi-meter (AC/DC volts, AC/DC 10 amp full scale, ohms). Will do pretty much everything you need of a basic meter.

A clamp on DC amp meter/current clamp is a bit of an issue... Typically, they are not cheap, and usually not that accurate (especially around zero to a couple of DC amps--they tend to drift from zero).

Here is a website with basic instructions on how to use a DMM.

I am sorry about your friend (and for his family)--Life (and death) is rarely fair.

Regarding Battery Monitors; AGM's almost requires a Battery Monitor so you know what is happening with them--I have not used any of them, but the Trimetric is a good starting point. The Xantrex models include a programmable output that you can use as an alarm or to turn off your inverter when you hit 50% (program to your needs) battery state of charge (other brands/models may have outputs too). If your spouse, kids, friends, etc. will be using your off-grid system, a Battery Monitor makes it much easier to explain what to do (50%/alarm, turn off loads and/or start genset until batteries are >80% charge).

The other reason I like them is they really quickly and clearly tell you when something is going wrong (such as batteries not charging or too much usage for poor weather conditions).

There are others here that can add their experiences too.

For me--I am probably more of a mechanical guy at heart--I still like the water analogies when describing electrical issues (pressure=volts; flow=amps, restriction=resistance/ohms; momentum/water hammer=inductance; switches=valves; etc.).

-Bill

niel · November 2009

Re: New to this site

hi and welcome jeff,
i think the problem may be deficit charging of the batteries as the pvs will be about 1.85% on charge rate to those 6 strings of 190ah batteries. you need about triple that % to properly reach a good charge as a 5% rate should be your minimum goal. the batteries may indeed be damaged now and new ones will go the same route if not properly charged.

Jeff G. · November 2009

Re: New to this site

Hi Bill and Niel,
Thanks so much for the help. I have a lot to learn,
Bill I have a good DVM and am now planning a battery monitor purchase.
Niel does what you have said mean that my 4 185 watt panels are not enough to charge my 6 strings of 24v 190 amh batteries? I only use my camp about every 3 weeks for a couple of days and then the batteries are charged for about 3 weeks without draw on the system. If this is true what is the formula?
Boy do I have a lot to learn
Jeff
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icarus · November 2009

Re: New to this site

Jeff

I suggest that you look here:http://www.batteryfaq.org/ and here: http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

Most people starting out destroy a battery or two before they really get the hang of it. The other thing that happens is that most people overestimate the amount of solar gain they actually get into the batteries, they overestimate the state of charge, they under estimate the loads they put on their batteries and underestimate how far down they routinely draw the battery down. Hence,, a battery monitor is a must. Not perfect, but a pretty good "gas gauge" to see where you are at any point in time. I really like the Bogart Tri-metric. The fancier Bogart is well though of as well.

Good luck, welcome to the forum. It looks like you have the start of a nice system Read all you can, and use the resources here. There are some very smart folks who have forgotten more about this stuff than most of us will ever know, meaning that we don't have to be constantly re-inventing the wheel.

Tony

peterako · November 2009

Re: New to this site

Hi there i see a problem you have 6 strings of 4 battery's (6 V 190 AH), That means that you have a battery bank from 24V 1140 AH ( not 190AH ).
Your solar panels 4 X 185 W 24 V That means 4 x 185 = max.740 W. That is to low to really charge the battery bank plus your tracker and inverter are using energy even if you are not there.

Use a generator and a charger to charge the battery bank minimum 60 A.
Do this fast because your battery's are low and this is costing there life time.
If you do not have a charger rent a truck 24V 100A charger plus generator soon.

Second problem 6 strings parallel is not a good system to balance a battery bank, i personal always say not more then two battery's parallel.

I do not see fusses on the photos i always install on every battery bank a fuse. if one battery is going bad the high current can burn down the place the same counts if a small animal starts tasting your cables.

.

Greetings from Greece8)

BB. · November 2009

Re: New to this site

Running the numbers for New York, NY. For 1kW of solar panels (minimum supported by website) using the PV Watt Website, and a derating of 0.52 (end to end solar panel - 120 VAC efficiency) and assuming a 2 axis tracker:

"Station Identification"
"City:","New_York_Ciy"
"State:","New_York"
"Lat (deg N):", 40.78
"Long (deg W):", 73.97
"Elev (m): ", 57
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: 2-Axis Tracking"
"Array Tilt:","N/A"
"Array Azimuth:","N/A"

"Energy Specifications"
"Cost of Electricity:","14.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 3.84, 64, 9.28
2, 5.08, 76, 11.02
3, 5.65, 90, 13.05
4, 6.71, 101, 14.64
5, 7.05, 107, 15.52
6, 7.80, 111, 16.09
7, 7.71, 111, 16.09
8, 7.19, 105, 15.22
9, 6.29, 90, 13.05
10, 5.33, 82, 11.89
11, 3.32, 50, 7.25
12, 3.36, 54, 7.83
"Year", 5.78, 1041, 150.94

Say, you want to run from solar 9 months of the year and use a genset for backup 3 months of the year...

That would make February at 76 kWhrs per month per 1kW of solar panels the "break point even point"...

4x185 watts of panels = 740 watts of solar panels

Your system, in February, would generate:

76 kWhrs/month/1kW panels * 1 month/30 days * 0.740 kW of solar/1kW panels = 1.875 kWhrs per day of useful 120VAC power

Or 1,875 Watt*Hours per day estimated power available for February...

You can run the same calculation for November using 50 kWhrs per Month to see how they should perform now.

If you have a kill-a-watt meter handy--you can measure/estimate your daily loads.

For charging, normally, the recommendation is about 5-13% of the 20 Hour discharge rate (less than that, the batteries may not be charged well, or even completely--more than that batteries may run hot and/or be a waste of solar panels; depending on battery type).

6 strings * 190 AH * 24 volts * 0.05 min charge = 1,368 watts minimum of solar panels...

AGM's themselves probably work better below 5% rate of charge than flooded cells (lower losses, less self discharge than typical flooded cell batteries).

Normally, we don't recommend that you discharge batteries below 50% State of Charge -- so for your system, the useful storage would be:

6 strings * 190 AH * 24 volts * 0.50 max discharge = 13,680 Watt*Hours

And, roughly in November, that would take 11+ days of non-use (in November) to recharge 50% to 100% state of charge.

Normally, it is recommended that flooded cell lead acid batteries do not remain below 75% state of charge for any length of time (like a day or so maximum) as the batteries start to sulfate.

However, at least one brand of AGM's claim they don't sulfate like standard flooded cell batteries do--So, you probably need to do some research on your brand of battery (or call the factory rep.) and see what their recommendations are for storage below ~75% State of Charge.

-Bill

Dave Angelini · November 2009

Re: New to this site

With most of the previous advice I would have Wattsun build you a new frame for different and more panels. If you are offgrid in New York (yeek thats hard to do) I would try and get close to the full 125 sq. ft. on your AZ125. Your just going to keep eating batteries. Make sure your keeping them above 40F in winter and below 85F in summer. Good Luck!

niel · November 2009

Re: New to this site

from jeffg,
"Niel does what you have said mean that my 4 185 watt panels are not enough to charge my 6 strings of 24v 190 amh batteries? I only use my camp about every 3 weeks for a couple of days and then the batteries are charged for about 3 weeks without draw on the system. If this is true what is the formula?
Boy do I have a lot to learn
Jeff"

that's correct that the batteries aren't quite getting charged up. for long term situations where there is more time to build a charge to the batteries we would not recommend being below about 3% for the charge rate and you will have to be sure that at that rate that the power used has been able to be replaced in addition to losses and efficiency factors taking away some of the power to the batteries. a 3% rate of charge on the surface represents 100/3=33.33hrs of full sun before losses and efficiencies are also accounted for.
6 x 190ah = 1140ah total as was pointed out and 3% would be 34.2a with 5% being 57a.
now i am a bit confused that you would say you have 4 185w pvs when i see 6 pvs in the pic.

i am sorry to say that i also just realized that those pvs are not true 24v pvs as the voltage is not high enough to charge 24v batteries with an output vmp rated at 24.4v. this does explain why the voltage never got very high on the batteries. the batteries may be ruined as they have not been properly brought up to a full charge since you got them. new batteries will also not be properly charged unless the voltage can go high enough to properly charge them. if you elect to go with the same pvs then they would need to be 2 in series to reach the proper voltage. you would need many more of these pvs to reach the proper voltage and current needed for that big of a battery bank. those mitsubishi pvs in series presents a problem as the controller you have is not an mppt down-converting type and much of the power will be lost in the translation. i am sorry to say that you have thrown a lot of good money away by not having the proper pvs and the proper quantity of them for the system to work.
to get a working system again if you have the will and $ to do it may take a bit of digging and kicking things back and forth. the batteries you have may not be totaled, but they may have some life left to give with a reduced capacity. get a good charge into them and take voltage readings. the question is now how you will get them recharged to determine their condition? you may need to charge up a few batteries at a time either with the pvs rearranged in series to allow for the 24v batteries or take the batteries down to 12v and use the pvs as they sit now. some can be hauled away to get a utility powered charge into them.
note that my general calculations that i was running for charge percentages that i had made an assumption with a voc of 35v that is typical of 24v pvs to obtain a current. obviously this is not the case with those pvs and i wish you had asked us for advice before you had bought anything.

Jeff G. · November 2009

Re: New to this site

Wow everyone thanks so much for all the responses. It is going to take me a while to digest all this info and make sense of it. I am certainly struggling with the various % of charge numbers etc. I will post some specific questions to this as soon as I figure it all out.

Niel in sept 08 my original 6 50watt 12v panels were installed. In Oct 09 I replaced those with 4 185 watt 24v panels that are now powering my system.

Thanks, Jeff

BB. · November 2009

Re: New to this site

Niel's update to his last post sounds like it nails the issue... Your panel are not "24 volt panels" designed to charge a 24 volt battery bank... But true Vmp=24 volts which is not designed to charge a 24 volt battery bank:

If I have the correct ones:

Mitsubishi PV-MF185UD4

Pmax @ STC 185 W
Pmax @ PTC 164 W
Vmp at Pmax 24.4 V
Imp at Pmax 7.58 A
Voc @ STC 30.6 V
Voltage change -106 mV/C

Basically, to fully charge your battery bank the panels need to be at least Vbatt-max+1-2 volt or around Vmp>=26+ volts on a hot day (these ratings are for "standard temperature" which overestimates that actual Vmp/Pmp ratings of the panels).

On a hot, windless days, the Vmp of your panels approaches 19.5 volts under full load... Well under the ~25 volts need to charge a room temperature AGM battery bank.

Your two optimal choices are to 1) buy a new solar charge MPPT based controller and put the panels in series (two in series, then put the two strings in parallel)... Or 2) replace with a set of "12 volt" or "24 volt" panels to use with your existing charge controller.

You can use the Xantrex XW String Sizing Tool website to look up panels and see how to set them up (series/parallel) on a standard MPPT type 60 amp charge controller.

-Bill

westbranch · November 2009

Re: New to this site

Jeff, I'm not any type of expert here but from personal experience, and what Neil, BB and the others have stated:

1 get a gen/ charger and 'boost' those batteries ASAP

2 get a true MPPT Charge controller like an MX 60 ( now discontinued) that down grades the incoming PV V's to batt bank Voltage
3 reconfigure your PVs to a 48 V configuration
4 get a good battery Monitor or 2 with temp sensor (preferably on that will 'hold' data for a 2 - 3 week period that you can retrieve when you are on site)...
5 go to the battery manuf. site and locate the Absorb and EQ settings for your batteries and set the float V at v EQ for one of your away periods ... yes there is an EQ Voltage for most AGMs and it is usually the top end of the Absorb range, but you will probably have to wade through the manual to find it in the fine print.. this is to try to recover the batts and should be lowered later. Mine can be EQ'd for 12 or 24 hrs but I only get a few hours of Float in the winter max, if at all, so I dont worry about over EQing... you may be the same if in upper NY or ?

when you come back be prepared to record the input / output to your bank, get it into a CPU and plot it in Excel or ?? so you can look at the graphs and the visual may quickly lead you to an answer...

and then reread this string

PS We have a similar issue in progress... slowly resolving

HTH8)

Eric

Jeff G. · November 2009

Re: New to this site

Thanks everyone once again, West Branch thanks for some eaiser to follow instructions, I will begin trying to fix some of the wrongs but it will take a few weeks or more. As to changing to 48 volts, I don't think that will work with my inverter but I will check.
Thanks again
Jeff

niel · November 2009

Re: New to this site

jeffg,
you have enough facing you without changing the inverter too. yes, by all means get those batteries fully charged asap somehow.
before charging you should number the batteries and with either a dvm or a dmm measure the at rest (greater than 3hrs without a load or a charge source to it) voltage of each battery and mark it down. please report this to us.

Bigwooo · November 2009

Re: New to this site

peterako wrote: »

I do not see fuses on the photos i always install on every battery bank a fuse. if one battery is going bad the high current can burn down the place the same counts if a small animal starts tasting your cables.

Not to get too far off track, but I have a question about fuse placement. I have breakers between my batteries and the charge controllers, and between the batteries and the inverters. Are you referring to something in addition to this?

peterako · November 2009

Re: New to this site

It is a system that i use, that does not mean that it is used in other parts of the world.
I always install fusses on the supplier, meaning charger and battery and that based on its rating.
Special for battery's a fuse on a inverter is not protecting the cable to the inverter. And special when there are parallel battery's. if one cell is shorting it will great a problem. If you drop a tool ( yes it happens ) or some body is connecting wrong a new piece of equipment ( yes also that happens ) the only bad thing after the short flash is a burnt fuse.

Breakers are good to separate and work safe or check battery's, but a fuse must be on the battery terminal.

I have seen a local station from the power company after that a worker drop t a tool on the battery's. the short wash before the fuse ( safety rule only stated that the breaker must be open ) Burnt copper and acid wash in every corner.

seeing a photo as before i aware from to good meaning by the installer. but fire life safety plus damaged equipment logic is telling me install fuses on the battery terminal.

Greetings from Greece8)

nigtomdaw · November 2009

Re: New to this site

Just to help you on the battery monitor front as you have a Magnum Inverter and the magnum LCD remote control you would be best advised to go for this and save some money

http://www.magnumenergy.com/BMK.htm

I checked our host store who is a Magnum dealer but he doesnt list it, Im sure he can get you one but it will be the best intergrated solution and cheapesssssssst once you have rectified your panel configeration, even a battery monitor cant solve that it will just confirm as previous posts and Neils discovery of not enought pressure (volts) to pump in to your batteries

HTH Nigel

nigtomdaw · November 2009

Re: New to this site

Also another superquick easy emergency fix is to wire two sets of two panels in series and then in parallel to your charge controller, which from your picture is a tristar which according to the specs here is

http://www.morningstarcorp.com/en/support/library/TriStar%20Datasheet%20English.pdf

The Tri Star has a max PV in voltage of 125v and your panels VOC voltage open circuit (ie max voltage they can produce ) is 30.6 v so 2 in series will max out at 61.2v. Thus they will not damage the controller. But leave the controller set to 24v do not change to 48 volt

This will give you the pressure (voltage) to flow power into your batteries albut at half the flow (current) but better than no charge (flow) at the mo:p

This is a halfway house emergency solution to it before a MPPT charge controller like the FM60 or XW60 or the new Tristar MPPT.

Jeff G. · November 2009

Re: New to this site

Thanks again , I ordered an expensive monitor and they are out of stock, I will call them tomorrow and cancel and try the magnum monitor.
Jeff

Jeff G. · December 2009

Re: New to this site

hi guys,
Thanks again for all your help. I have not fixed things yet but have all the new parts needed except a few mor Battery cables to install a shunt for the batt monitor and a couple of breakers between the batt and inverter and batt and charge controller. I have the new Outback MPPT controller and temp sensor. Some good news is it seems the battery bank has slowly regained some life the voltage has been up a few volts to 28 and change when I arrived this weekend this is the reading without letting them rest for a few hours. I have learned a little more about the batteries and % charge numbers.
Jeff

Jeff G. · January 2010

Re: New to this site,

Hi Guys
Thanks again for all your help. I have finally completed the changes and up grades (last week). I installed an Outback 60amp MPPT charge controller, the appropriate circuit breakers between batt and controller and controller and inverter. Intalled a battery monitor, temp sensors. I put my 24v panels in series to be 48 plus volts.
I believe my batts will never quite be the same as they were but they seem to be adequite to get the job done, when I arrived this weekend I was happy to see that the string was up to 28.1v (it had not wanted to go above 25.5v) and worked well and even recharged decently on a cloudy snowy day.
I still need to learn what all the data I now get means. I did reset the low voltage disconnect to 23.8v so as not to run the string down to far and further damage the batteries.
I do have a couple of new questions and problems with a seperate solar powered alarm. It decided to die about 4 weeks ago. After a very bad storm with strong winds the alarm went off. I am not sure if things falling off the walls set of the motion sensor or if the voltage dropped so low that it went off. It is a 12v powered alarm not hooked to a monitoring station. When I reset everything the batts would not charge so I changed out a batt and it still did not charge. I then changed the charge controller with my no longer used morningstar but it still did not charge. The pv incoming voltage reads 26v but I don't get a reading coming out of the charge controller on either the Morningstar or my older trace 40.
My new questions are can a panel read 26v (this is an older single panel that should put out between 26 to 28 volt) and not put out amps or watts in other words voltage looks correct but it does not supply enough current to charge the batts. Is there a way to bench test my charge controllers?
My temp fix was to turn the alarm system to AC and leave a 13 watt light bulb on to keep the inverter running. I have to think it is not in my best interest to keep the inverter constantly running.
Thanks, jeff
Still lost but not as far away now.

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