Batteries - Massive Parallel and Series Issue- 3 questions

I have 12 strings of 4 batteries each (all Deka 9c12's ~~220ah). there is a mixture of ages (12 - 2 years old, 24 - 1 year old, 12 6 months old)

How do I detect a bad battery ??? System does not have the "Staying Power" it used to 2 years ago.
What is the best way to equalize them all ??
How do I replace / charge a battery/batteries into the battery farm ?
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    I don't recognize the model number. Are these flooded cells or sealed/AGM?
    Flooded cells is easy; just take specific gravity readings of all cells. It won't tell you the capacity, but it will indicate differences in SOC which hints at differences in capacity.

    Sealed batteries are more difficult to judge. The best you can hope for (failing the ability to do an actual load test) is to fully charge each one individually and let it sit over night and see how the resting Voltage holds. This is far less than perfect testing. But if you have some that won't charge up to full Voltage or that fall off considerably overnight you know those aren't up to snuff.

    You really should not have twelve parallel strings of batteries, never mind of different ages. Time to re-evaluate loads, re-configure the battery bank, sell the old off as scrap, and get a few capable of meeting the needs with less than four parallel strings. It will perform better all-around.
  • pvoffgrid
    pvoffgrid Solar Expert Posts: 48 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    Hi,

    I am a new guy here also but here are my answers.

    How do I detect a bad battery??? System does not have the "Staying Power" it used to 2 years ago. Get a meter and check the voltage across the terminals. The ideal way is to disconnect each battery from each other so you have individual batteries to check. And, check them after they have sat for a few hours. However, given there are so many to check you can check them while all still connected but it is not a true/best/most accurate method, as compared to disconnecting.

    What is the best way to equalize them all?? I have a Kohler 11RMY generator that has an equalize setting on it which means the generator will run the voltage on the batteries up high, to your setting, let it drop slightly, and keep it there for a few hours. So, you will need a generator to equalize them as this all I have ever known.

    How do I replace / charge battery/batteries into the battery farm? I am shutting my entire system down: turning the inverters off 1st and then turning off the breakers on the main PV panel (4 switches: 2 smaller ones on the side, 2 big ones on the front). I then disconnect the battery I am changing and put the new one in, reconnecting it, and then turn everything back on in the opposite order I turned them off.

    I am curious to see other replies to see if I am doing this correctly myself, but...this is how I am doing it now and it seems to work, although there is another issue with my system...I think.

    48v Off-Grid

    Modules: 5.395 kW:

    (16) Kyocera KC130TM

    (12) Kyocera KD-210GX-LPU

    (3) Kyocera KU265-6MCA 

    Batteries:

    (24) Trojan Solar SPRE 02 1255 

    Racks:

    (2) Zomework trackers (KC130TM modules, 8 per tracker, landscape position) - facing due south

    (1) Unirac ground mounted fixed rack (all KD210 modules, landscape position) - facing slightly southwest

    (1) Unirac roof mounted fixed rack (all KU265 modules, landscape postion) - facing due south

    Inverters:

    (2) Trace SW5548

    Charge Controllers:

    (1) Outback MX60 - for (16) KC130 modules 

    (1) Flexmax60 - for (12) KD210 modules

    (1) Flexmax60 - for (3) KU265 modules

    Generator:

    (1) Kohler 14RESA propane

  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    These are all FLA batteries used with floor scrubbers, about ~100 lbs each. How do I get them all to a full state, if some are bad ??
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    First, make sure you have a "balanced" wiring for the battery bank (equal length current paths for all wiring paths). The Smart Gauge website has a good article.

    Regarding understanding your battery bank, here are a couple of good Battery FAQs:

    Battery FAQ
    www.batteryfaq.org

    Next, a good digital meter (suggest a DMM+DC Current Clamp Meter like this one for ~$60 is "good enough" for our needs here) and a hydrometer. The steps I would go through:
    1. Measure and log the temperature corrected specific gravity for each cell. Never let plates be exposed, do not over fill cells, you should need to refill a cell about every 2 months or so--Filling too often may indicate over charging, going 6-12 months without filling may indicate under charging (different battery types can have different water requirements too).
    2. Inspect wiring, clean connections and add anti-corrosion grease, re-torque bolts, etc.
    3. Use the Digital meter to measure the voltage of each cell or each battery). You are looking for differences and absolute value
    4. Use a DC Current Clamp meter to measure the current through each parallel string during both heavy charging/discharging--You want current balanced between all strings.

    So, with all of the above information, you want:
    • Battery to cycle between 50% and 90% state of charge during normal operation, never below 20% state of charge, and recharge >90% state of charge once or twice a week (at least). 100% state of charge (+equalization if needed) around once per month (this is subject to lots of debate here--seems to depend on brand/model of batteries--typically a bigger issue with larger industrial type batteries).
    • The hydrometer will give you the "exact" state of charge for each cell. If there is a large variation between cells (on the order of 0.015 to 0.030 or or greater, try equalization to bring cells back together--If you still have very low cells, they may be sulphated and ready for replacement).
    • The voltage measurements will show you high voltage/low voltage cells... May indicate open or shorted cells. Open cell can drop a string out of the bank, and a shorted cell can discharge the whole bank (while overcharging the one string it is in).
    • Current Clamp measurements will show how effective each string is. If you see over a 2:1 between high and low string currents (i.e., 20 amps in one string,
    • 10 amps in another), you probably have some issues to look at (bad electrical connections, open/shorted cell, etc.). Do the measurements both under heavy charging and under heavy loads.

    A battery bank that is slowly going bad may indicate "deficit charging" (and low water usage would also help to confirm under charging)--Using more Amp*Hours from the battery bank than you are returning via charging. A larger solar array may be helpful here. Also, a Battery Monitor will make day to day operation much easier (and for spouse/kids/guests easier to understand how to take care of the battery bank without using a hydrometer or guessing with a volt meter).

    If the battery bank is being heavily cycled, and you have sufficient solar resources, then you might try raising the Absorb Set Point (perhaps a 1/2 volt at a time) and/or increase the Absorb timer (from 2 hours to 4-6 hours), and/or reduce the Absorb termination current (if present in your charge controller).

    Personally, I am not a fan of a massively paralleled battery bank. It makes maintenance more work (lots of cells/connections to inspect) and difficult to ensure proper current sharing between parallel strings. Also, each parallel battery connection should have its own fuse/breaker per string (for electrical safety)--And it gets expensive to do large numbers of circuit protection devices.

    At 2,640 Amp*Hour battery bank, your "ideal charging current" is in the range of 132 amps to 264 amps to 343 amps (5/10/13% rate of charge). Those are pretty heavy currents and a very large battery bank. Do you have enough solar array and backup battery charging power (genset/mains/etc.) to keep them well charged?

    My two cents worth of suggestions... I would look at a 48 volt battery bank (yea, new inverter, possibly new backup AC battery charger) to reduce charging current and the number of parallel battery strings. And I would look at larger AH rated batteries / cells. My personal suggestion is to aim for a 1 string battery bank with 2-3 strings maximum.

    Questions?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    Disconnect and inspect.
    Tedious work ahead.
    Take the caps off the cells, use a hydrometer to check the specific gravity in every one.
    Try to match up batteries in a string so that all in that string have similar SG.
    Charge one string at a time fully. Equalize to get the SG per cell as close as possible.

    And again know in advance that twelve parallel strings is not going to work well or for long. There's no way around that, as the resistance per string is inevitably different and will vary more with SOC making it impossible for all batteries to share current equally when charging and discharging.
  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    I also have an Infared temp meter that reads battery temp, will that be usefull ??
  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    All battery cables are 4/0 cable, the common bus (+ and -) is a 3/4 solid copper grounding rod (about 12 feet long). The copper grounding rods have two 4/0 cables (on both the + and -) to the battery disconnect.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    It can be a quick way to find hot spots when the battery bank is subjected to heavy current (look for over heated wires/connection points).

    Overall, if the battery gets too hot (over ~110-120F), you would need to cut the charging voltage/current until the battery bank cools down.

    I think the DC Current Clamp DMM + Hydrometers are your two most important tools here.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    Hi rt,

    IMHO, your battery configuration is just plain NUTS!

    With 48 batteries and 288 cells to check, water and read SGs, it would be a full time job to to it correctly. Then there are the string balance issues, then there are the issues of temperrature variations across these strings, not to mention even getting access to all of the batteries to do meaningful measurements. What FUN!

    Assume that these batts are all on a single system ... The 5548s have about 300 A charge capability total, although the genset is a little bit light in capability, but perhaps the Hydro can make up for any of this.

    Peraonally, would try to run a single string of batteries. Two max for me, as any more strings is just too difficult to manage without making it a full-time job.

    As others have stated, charge the bank as well as you can. Disconnect one or two strings from the rest of the bank. You can leave the series connections intact as long as they have no other connections to another string. Let them rest overnight. Measure the resting V, and ideally SG of each batt/cell. Select the best of these, repeat until you have the best and worst separated. You can try charging and EQing some of the best of the worst as a separate string, rinse and repeat.

    It will be good to keep a log of the status of each battery.

    Is'nt this FUN?

    Opinions differ, but your system may be a case-study in many multiple strings, and the advantages/disadvantages of multi-multi strings.
    Wish you the best possible luck! Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    Thanks to All !!!
    So I got some work to do
    1. charge each string to 58vdc individually
    2. engage all strings together
    3. do massive discharge, and check amperage load on each string
    4. do massive charge and check amperage load on each string
    5. after identification of weak strings, then do battery by battery analysis
  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    do you have a hydrometer? you need to start with their SG s and look for the bad cells. I'm surprised they lasted this long with that many strings. You probably need to replace most if not all with 2V cells x 24 for 48v.

    Add: quick way to start finding weak cells is with a volt meter. Number each battery, then record its voltage before starting to charge, WRITE the voltage down!... then you will know what you started with and if the charge actually did something...
     
    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
  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    You've already been told that massively parallel battery banks don't work.
    To understand a little more about why that is, read: http://forum.solar-electric.com/showthread.php?14674

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    rtribble wrote: »
    Thanks to All !!!
    So I got some work to do
    1. charge each string to 58vdc individually
    2. engage all strings together
    3. do massive discharge, and check amperage load on each string
    4. do massive charge and check amperage load on each string
    5. after identification of weak strings, then do battery by battery analysis

    Is it even prudent to continue talking about this ? If one string is half a volt different and you connect it up
    to the rest of the battery array, the sparks are going to fly ! I think you need to be checking each battery (not strings, or banks, but individual batteries) with a decent smart charger, and load tester, and if it passes, then add it to the array, but what I hear you describe sounds like a nightmare.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    mike95490 wrote: »
    what I hear you describe sounds like a nightmare.
    Have to agree. An unworkable nightmare and a bottomless pit for the inflow of money, unless major changes are made on almost every level.
    As it presently stands, this is a case study on how NOT to build an off grid electrical system.
    So sad to see this happening, as very soon another apparently misinformed and uncomprehending user of solar electricity will wrongly come to the conclusion that solar power is both unworkable and a horrible waste of money. :cry:
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    rtribble wrote: »
    1. charge each string to 58vdc individually

    Are you sure that's the right voltage for those batteries, and that you haven't sulfated them? They are the same battery as the Interstate U1850S/U1850HC for floor scrubbers (both brands are made by Johnson Controls and they are the identical same battery) and the recommended absorb voltage is 2.58VPC. I have never seen a charger for that style battery yet that absorbs at only 2.4VPC. If you have been absorbing those at 58.0V, yes indeed, the "zip" is going to be gone from them.
    --
    Chris
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    I am not sure these are the best battery choice for RE to start with. With the amp hrs of storage vs the cost there is no way that you'd ever come out on them. I looked at them once and concluded they were just not viable @ $184.00 even at Sams Club.
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    I am not sure these are the best battery choice for RE to start with. With the amp hrs of storage vs the cost there is no way that you'd ever come out on them. I looked at them once and concluded they were just not viable @ $184.00 even at Sams Club.

    Actually, they're pretty good because they are a six cell 12V type. 228ah @ 12V is a 2.7 kWh battery. The typical 1380ah 2V cell is also a 2.7 kWh battery, so there's no difference in energy storage capacity. The infamous Sam's Club golf cart battery is 232ah @ 6V, or about 1.39 kWh.

    We have six parallel strings of 4 x Rolls T12-250's for our bank with absolutely zero problems with balance issues between the strings. So IMHO the dreaded parallel configuration of batteries is over-rated. Large parallel banks have been used for for years in marine house power and heavy equipment applications with way less problems than series strings. In mission critical applications like marine, the parallel strings provide redundancy in the event of a failed battery, where a single failed battery in a series string knocks the whole string offline, and that is why series configurations of battery banks in yachts and such are avoided like the plague. A typical 50 foot yacht has a 36V battery bank that puts most RE banks to shame for capacity and size. And having the radar, radios, HVAC, lighting and all the navigation equipment go dead because of one bad house power battery is simply not acceptable in the marine world. So it's all a matter of perspective.
    --
    Chris
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    ChrisOlson wrote: »
    Actually, they're pretty good because they are a six cell 12V type. 228ah @ 12V is a 2.7 kWh battery. The typical 1380ah 2V cell is also a 2.7 kWh battery, so there's no difference in energy storage capacity. The infamous Sam's Club golf cart battery is 232ah @ 6V, or about 1.39 kWh.

    We have six parallel strings of 4 x Rolls T12-250's for our bank with absolutely zero problems with balance issues between the strings. So IMHO the dreaded parallel configuration of batteries is over-rated. Large parallel banks have been used for for years in marine house power and heavy equipment applications with way less problems than series strings. In mission critical applications like marine, the parallel strings provide redundancy in the event of a failed battery, where a single failed battery in a series string knocks the whole string offline, and that is why series configurations of battery banks in yachts and such are avoided like the plague. A typical 50 foot yacht has a 36V battery bank that puts most RE banks to shame for capacity and size. And having the radar, radios, HVAC, lighting and all the navigation equipment go dead because of one bad house power battery is simply not acceptable in the marine world. So it's all a matter of perspective.
    --
    Chris
    We must be talking about a different battery, the ones I saw were 155 amps, 20 hr rate @ 12 V. If they are 228 amps, then thats different.

    http://www.samsclub.com/sams/duracell-golf-car-battery-group-size-gc12v/prod3870120.ip?navAction=push#spec
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    We must be talking about a different battery, the ones I saw were 155 amps, 20 hr rate @ 12 V.

    http://www.samsclub.com/sams/duracell-golf-car-battery-group-size-gc12v/prod3870120.ip?navAction=push#spec

    Not even close to the same battery. The Deka 9C12/Interstate U1850HC are 228 ah @ 12V. They are a tall-case like our Rolls T12-250's, and are designed for repeated deep cycling to 20% SOC on floor scrubbers and floor sweepers. That Sam's Club battery is a light duty Golf Cart format Group GC12. The dry weight of the Interstate U1850HC's are are 117 lbs and 144 lbs full of electrolyte. So they are basically double the size and weight of a GC12, they hold roughly 3 gallons of electrolyte, and they have over 3" of electrolyte capacity above the plates.

    The 9C12/U1850 is one heavy duty battery, easily on par with the Rolls T12-250, but at a cheaper price and less warranty.
    --
    Chris
  • Blackcherry04
    Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    ChrisOlson wrote: »
    Not even close to the same battery. The Deka 9C12/Interstate U1850HC are 228 ah @ 12V. They are a tall-case like our Rolls T12-250's, and are designed for repeated deep cycling to 20% SOC on floor scrubbers and floor sweepers. That Sam's Club battery is a light duty Golf Cart format Group GC12. The dry weight of the Interstate U1850HC's are are 117 lbs and 144 lbs full of electrolyte. So they are basically double the size and weight of a GC12, they hold roughly 3 gallons of electrolyte, and they have over 3" of electrolyte capacity above the plates.

    The 9C12/U1850 is one heavy duty battery, easily on par with the Rolls T12-250, but at a cheaper price and less warranty.
    --
    Chris
    Oop's , My bad , I see it now. I looked for that battery and didn't find it till you pointed it out. Thats a whole different deal.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    The problem of current sharing between parallel battery strings is not a matter of opinion or point of view, it is a matter of physics. Comparing systems with redundant parallel batteries to ones where the goal is to make them all work as a whole is not equitable. It is not a problem that shows up quickly or as a sudden death situation, but rather as greater diminishing of capacity over time with inequities between the strings increasing as usage continues. Ultimately it does shorten the lifespan of the bank, but over years not days. When planning an RE system long-term value should be a goal. It is unlikely the marine applications cited use their batteries in the same way or for the same time as an off-grid solar set-up.

    The fact that Chris has six banks in parallel working well shows two things: 1). he's paid careful attention to the wiring and 2). they haven't been in place very long.

    The unfortunate truth is most people have difficulty with keeping one string of batteries up to snuff, never mind more.

    As always, everyone is free to ignore my advice. It's your money you are spending, not mine. ;)
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    The fact that Chris has six banks in parallel working well shows two things: 1). he's paid careful attention to the wiring and 2). they haven't been in place very long.

    Our bank is two years old this month. There are some other advantages with parallel strings - load capacity and charging amps. If the bank is loaded or being charged at 120 amps, as an example, the amp load on each battery is a small portion of what it is on a series string. As an example, if we had twenty four 2V cells being discharged or charged at 120 amps, every battery in the string has to deliver or accept 120 amps. With six parallel strings, each string (and every cell in the string) is being discharged or charged at 20 amps instead of 120 amps.

    There's a big difference in the capacity of your bank when you discharge at the 20 amp rate during heavy loading on the bank vs the 120 amp rate, no matter what type of battery it is. So if you run your inverter at continuous high loading, parallel strings are necessary to prevent severe voltage sag - you're discharging each battery (and cell) at a more reasonable rate.

    Same applies to charging, as to discharge.

    So basically, anybody that has a high capacity system is going to have multiple parallel strings. It's a necessity due to the limitations of series connected batteries.
    --
    Chris
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    rtribble wrote: »
    I have 12 strings of 4 batteries each (all Deka 9c12's ~~220ah). there is a mixture of ages (12 - 2 years old, 24 - 1 year old, 12 6 months old)

    Just to beat this poor dead horse;

    This battery array is HUGE, and has all of the most common issues that come with multi-multi strings -- far too many parallel strings of differing ages. It is very difficult to manage the parallel connections, and any meaningful maintenance is out of the question. A bank like this requires careful monitoring, which is essentially impossible with 288 cells to monitor SGs, and fill ... can anyone imagine just how often one would like to take the day or so required each month to do this??

    Some people can keep parallel strings of batts tamed, BUT, I have just not seen systems where more than two strings are doing well after about two years of off-grid use.

    Marine use of house banks is different than the typical Solar based off gird use, and IMHO, Floor Scrubber batteries need a hot high-current recharge from a typical cycle of 20% SOC or lower, which also differs from the typical Solar applilcation.

    For large banks in Solar-based off grid applications, there is a lot to be said for 2V batteries, or at least batteries with easily removeable 2V cells. With a good inverter, this could accommodate the situation where a single cell goes bad -- running on N-1 cells until a replacement becomes available.

    These are just my opinions. Every system designer has a different cut on things. Chris, you have abilities that most of the off grid folks that I know, simply are lacking. What you can keep running is not typical of what we see in our local area.

    Not to pick the nit too finely. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    I would term it more as attempt to avoid over 2-3 parallel strings--rather than say it won't work. Because, it does for many people (and industries).

    Massively parallel banks just have a lot of maintenance/debugging/costs and other issues that make parallel strings a lot less desirable for somebody that does not want to add battery tech to their resume.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    Vic wrote: »
    These are just my opinions. Every system designer has a different cut on things. Chris, you have abilities that most of the off grid folks that I know, simply are lacking. What you can keep running is not typical of what we see in our local area.

    I am less concerned about the wiring configuration of the OP's bank than I am about how they are being charged. The chargers used for floor scrubbers and sweepers have what is called a "finishing stage" that RE chargers don't have. The batteries in those applications are usually run until the machine barely has enough power left to get it back to the charging station and they do a low-voltage bulk, absorb and finish stage, then shut off and do not float them. The voltages used in those chargers (and the batteries designed for it) are higher than 2.4VPC. They charge at like 14.1 volts until the amps drop to a certain point, then go up to like 14.5-14.7 volts for absorb, and finally 15.5 volts for the finish stage - and the whole process takes 10-12 hours.

    RE chargers do not do this, so any battery designed for floor sweepers and the like is not going to last in an RE application because they're not being charged right.

    My 2 cents on it is that that's the problem with why the batteries in question appear to be "weak". They've been chronically deficit charged according to what is used in the industrial world that they were designed for. I believe the type of charger used for floor sweepers and forklift batteries, et al, are called "constant current" chargers.
    --
    Chris
  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    OK,I screwed up guys, got it ! so what best to do now that I have invested in 48 batteries (about $10K). No more investment here..

    I have a 12 v auto battery stress tester, I will start with a battery by battery test. weed out the bad and rearrange the strings..

    The next try will be a massive 2V string at about 2K ah. and have separate strings for each set of Trace 5548's
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    Chris makes another good point: wrong batteries for the application. Seen it, over and over. Doesn't matter how good the wiring is then; if the charging profile is wrong the batteries suffer.

    Trouble is the OP has both problems. In spades.
  • rtribble
    rtribble Solar Expert Posts: 28
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    ChrisOlson wrote: »
    I am less concerned about the wiring configuration of the OP's bank than I am about how they are being charged. The chargers used for floor scrubbers and sweepers have what is called a "finishing stage" that RE chargers don't have. The batteries in those applications are usually run until the machine barely has enough power left to get it back to the charging station and they do a low-voltage bulk, absorb and finish stage, then shut off and do not float them. The voltages used in those chargers (and the batteries designed for it) are higher than 2.4VPC. They charge at like 14.1 volts until the amps drop to a certain point, then go up to like 14.5-14.7 volts for absorb, and finally 15.5 volts for the finish stage - and the whole process takes 10-12 hours.
    -
    Chris

    OK so what settings do I use on my 5548's for bulk/absorb/float ? and on my MX60's for same.
  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions

    I use Floor Scrubber batteries to run a 24 year old chest freezer. I got 3 Crown T185's (185 AH @ 12 VDC each) for $25 each that had been wired in series for the 36 volt floor scrubber. They were about 11.2 volts each when I got them. I charged them up, and am running 3 in parallel to run a 24 year old chest freezer from a 12 volt Exeltech XP-1100 inverter. This will also run the frig' too I hope until they die and then I'll scrap them and get something else. These have been working great for 5 months now and use not very much water and stay well above 12.3 volts 24/7 when there is enough sunshine. There will be a 200 amp magnetic breaker on each string of batteries (80 volts DC 200 amps Airpax magnetic breaker for $20 each new) Currently there is only 1 breaker from the paralleled batteries to the bus bar and it is a 175 amp magnetic from NAWS.

    I am a fan of 2 volt cells, but it is difficult to find enough that match used, but I do have my eye on some 1495 AH 2 volt cells.....

    rtibble: If I were in your position I would consider putting 3 strings on each 5548 and it should be much more managable. You keep your capacity and just have to set up the chargers and panels a bit differently. I have my incoming strings of panels switchable to different charge controllers so I can change how much power different charge controllers get. Very handy if you want to bulk charge some, then as the charge tapers off, you can switch some of the panels to other duties and it gives you many options rather than just hard wiring them in a fixed position. I use the Blue Sea switches for routing where the panels are going to go. There are currently charge controllers dedicated to each battery pack with a dedicated BTS so they get as well cared for as I can. This plan also gives backup as you would have.

    Good luck and guys like you make guys like me think so it is helpful sharing both good and bad. I am tired of being the bad example around here. Hehehe :-)

    Skip
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
  • ChrisOlson
    ChrisOlson Banned Posts: 1,807 ✭✭
    Re: Batteries - Massive Parallel and Series Issue- 3 questions
    rtribble wrote: »
    OK so what settings do I use on my 5548's for bulk/absorb/float ? and on my MX60's for same.

    This is the charging algorithm used for the 9C12/U1850-series batteries with an industrial I-E-I charger:

    The first rate charge is continuous until 2.4 volts per cell is reached. This current rate should be C/5.

    At 2.4 volts per cell the second rate activates at a constant voltage of 2.45 volts per cell for 4 hours.

    The third rate is constant current at C/30 until 2.58 VPC is reached, at which point the charger turns off.

    Bottom line: you do not have the required equipment to charge those batteries properly. They are industrial/traction batteries - NOT RE batteries. Your 5548's do not have industrial type I-E-I chargers in them. Using the 5548's at bulk voltage of 58.0 barely gets them thru the bulk stage, much less absorb and finish stages.

    I would suggest calling the manufacturer and find out how (or even IF) they can be properly charged with a standard RE bulk/absorb/float constant-voltage type charging. The RE world is typically way behind the industrial world in battery charging technology.
    --
    Chris