After equalizing, batteries getting too low

farmingsolarfarmingsolar Registered Users Posts: 3
Hi, this is my first post and any help is greatly appreciated. 

I have a 48 v battery bank with Magnasine inverter and outback controller. Had this system professionally installed 3 years ago and have been very happy with it until recently. Basically, I watered the batteries and attempted an equalization last week... after a couple hours the inverter gave a a high voltage warning and shut down. Now, for the past few nights, the inverter is shutting down the system, as it shuts down when only 46 v are being inverted. Despite owning this system, I do not have much experience with it and have just been consistent with watering batteries, equalizing and charging from the generator when things get low. I don't know much else, unfortunately.

Thanks!

Comments

  • mcgivormcgivor Solar Expert Posts: 3,063 ✭✭✭✭✭
    Have specific gravity  (SG) readings been taken? That would reveal what state the batteries are in, equalization if anything should have helped, voltage itself  is meaningless in determining the condition. When batteries have lost capacity they reach their terminal charge  voltage very fast and consequently also discharge very fast.

    Without SG readings this is mostly speculative, do you possess a hydrometer? 
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Sounds odd, I'd look through your settings if possible.  As I recall from my feeble mind. The Magna Sine has some of the highest and lowest voltage settings as presets, so perhaps your installer changed them? I think the high end is 64 volts for a 48 volt system...

    Having the low voltage now after the high voltage last week with equalizing, makes me wonder if you took any action when you had the high voltage shut down?
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • PhotowhitPhotowhit Solar Expert Posts: 4,994 ✭✭✭✭
    Might also give us the specs on your system. Wonder specifically if you are using 'Iron Edison' batteries which have a wider voltage swing than other batteries. Though Equailizing isn't generally needed with them and they would be an expensive choice and worth mentioning.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • EstragonEstragon Registered Users Posts: 3,939 ✭✭✭✭✭
    46v is certainly a concern.  I'd start by measuring the resting (not charging or discharging) voltage across each battery.  They should be pretty much the same.

    Also, when actively charging or discharging, do any cells seem hot (ideally measured, but just feel works)?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • farmingsolarfarmingsolar Registered Users Posts: 3
    Thank you all for the quick replies. 

    Here are some specs:
    (6) Renesola 260 watt solar modules
    - Magnum MS 4448 Inverter
    - Midnite Solar E Panel
    - Outback 60A Charge Controller
    - (8) Trojan L-16 volt 435 Ah batteries
    Midnite Solar DC Combiner

    Batteries are outside house, buried in insulated box.

    Yesterday I went in to measure with the hydrometer and batteries were HOT...I disconnected all loads and left the battery box open to cool overnight. These batteries have a watering system and I hooked up to water to see if they needed more and they took another 3/4 gallon (not sure if this is relevant...I had watered a week ago and system doesnt usually need much)

    I also noticed corrosion on two of the positive terminals! I did not notice the corrosion a week ago when I opened up to water / equalize but did not inspect closely so could have missed it. I know I need to clean the corroded terminals, but want to make sure I'm doing this right. The inverter is shut down, but do I need to disconnect the controller too before disconnecting terminals? And with the terminals, do I disconnect all the negative posts first, then the positive, clean, then hook up the positive posts then negatives last? I don't want to get fried.

    This morning, with the batteries cooled (still seemed warm) I took readings with the hydrometer. Each 6v battery has 3 cells and I measured each cell for each battery. I'm sure there is a correct way to write this out, but basically all the cells read between 1250-1275, except in one battery, which had two low cells:
    cell 1: 1100
    cell 2: 1100
    cell 3: 1275

    I do not want to run the system until I know it's not going to overheat and so we're staying with family for now (we have a newborn). Hopefully the batteries weren't hot like that for long and hopefully won't be damaged...besides the one.

    I also have a service call request with the company that installed this system, but have not heard back for a few days. 
    I really appreciate any follow up advice. Thank you for your time!


  • TecnodaveTecnodave Registered Users Posts: 412 ✭✭✭✭
    Farmingsolar,

    Yes definitely do shut down system before disconnecting batteries,  correct procedure,  first shut down solar input to Outback controller, wait a bit for residue electricity to be discharged , then shut down battery breaker for the Outback. Some MPPT controllers will be damaged by having input power with no battery to take that power. I have MidNite Charge Controllers and that is the recommended practice as per MidNite. 

    Disconnect negative first, then positive.  It looks like that you have a failed battery with that 1100 s.g. readings. If you have an old school 6 volt battery charger use that on the one weak battery to attempt to recover it. If you cannot get the s.g. up then it's time for a new battery. 
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    You can also use a voltmeter to measure the voltage across each 6 volt battery during charging/load/resting (3+ hours of no charge/discharge) to verify how the batteries are doing.

    In any case, you need to focus on that one battery with the two ~1.100 sg cells. You could try a 6 volt charger (or there are other ways to get "equalization" to that one battery without damaging the other 7 in your system (EQ is "controlled" over charging of your battery bank to get charging current to those 2 low cells--EQ is hard on the "good cells" and should be done only when needed, or once a month for short period of time to "mix" the electrolyte and bring all cells back to 100% SoC).

    My guess--That battery is "bad" and don't even bother trying to fix it (at least for now)... Just make the decision to buy a replacement battery or replace the whole bank (if old and having other problems)...

    If the rest of the bank is good--Just get a replacement battery (new or if you can find an otherwise good/used battery to save some money) and move on.

    Your batteries should last something like 5-8 years, and that one battery needs to be replaced. I would just buy the one and keep on doing what you are doing.

    I guess you are around Nashville Tennessee? Have you kept the battery bank relatively cool? Something around 75F? (hot would be a battery bank that is >~95F all the time). Hot batteries age faster (for every 18F/10C over room temperature, the batteries age 2x faster).

    Depending on which battery you have, there may be some pro-rated warranty still available:

    https://www.solar-electric.com/lib/wind-sun/Trojan_Limited_Warranty.pdf

    Typically, the only way those 2 cells could go bad--That you could cause--Overfilling (electrolyte spills out), or not using distilled water (some folks use filtered rain water). If you use hard water and/or water with organics in it--That can "poison" the cells.

    However, since you have 22 cells in good condition and 2 out of 3 bad cells in one battery--I would suspect that this is not your issue (unless you have kids that got to the battery bank and dropped bugs in two cells).

    When replacing the battery, get the same brand/model/type... Don't mix battery types in series strings--The cells/batteries need to be "matched" regarding performance so that they all play happily together.

    And when putting into service, the "replacement" battery should have SG within 0.015-0.030 (or closer) specific gravity (i.e., similar state of charge). That will work out best.

    Double check the replacement battery when you get it... Log the SG and resting voltage, make sure the batteries have no exposed plates (enough electrolyte). And do not fill the batteries to the very top--When they get hot and bubbling, the electrolyte expands and can be forced out through the tops.

    Other things to watch for--Water usage... Nominally, you should have to add water every 1-3 months (proper charging). If you are adding too much water/too often, back down on the charging voltage setpoints and/or absorb time. If you are not adding water, then you should jack up the charging voltage/absorb times a bit (double check setpoints against owners manual recommendations).

    Check voltage across each battery (different conditions: charging/discharging/resting)--It is a quick way to find "differences". You have 24 identical cells and 8 identical batteries... Differences usually indicate problems (or potential problems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • farmingsolarfarmingsolar Registered Users Posts: 3
    Thanks for the replies. The plot thickens, and I fear I may be screwed. After talking to my wife about the current situation I discovered that she had filled my distilled water jug with tap water this spring and I used this jug to add water to the batteries (added 1 week ago). It sounds like this could be the cause of the failing cells and probably ruin the batteries? Could this also cause the overheating? Do I have any options? So frustrating...she said she had to water something so used that jug and forgot it was only for the batteries.
  • BB.BB. Super Moderators, Administrators Posts: 29,485 admin
    Oh boy...

    Call Trojan and see what they suggest?

    About the only thing I can think of is the process that some folks have tried to "recover" old batteries and make them useful again.

    From what I recall, dump the electrolyte out of the batteries, fill with distilled water, "charge them", then dump out the distilled water and add electrolyte to the batteries (something like that--I can try searching the archives and see if I can find the process).

    Or, just replace the "bad battery" and see what happens. If there was sediment that got dump into the "last battery", it could account for why you have 2 bad cells instead of 24 bad cells. Whether or not the rest of the cells will go "quickly", slowly, or have their full life--It all depends on what the contaminants were and their concentration.

    Table 4, page ~15, water impurities and their effects.

    https://www.trojanbattery.com/pdf/TrojanBattery_UsersGuide.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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