Battery Failure

Good day all,

I'm new here, I have had some issues concerning a solar and backup system I installed 4 months ago. I used 12 units of 300w solar  panels, a 60a charge controller (Ipanda), and a felicity 5kva 48V inverter and 8 units of 200AH batteries running on a Load of about 2000W.

The system ran smoothly for the first 3 months, then suddenly system lasted for less than 2hours. I tested the internal resistance of individual batteries and 5 was replaced. I suspected the ambient temperature (36 degree Celsius) to have been the cause of the damage and ventilated the surrounding, and changed the interconnecting cables of batteries from 25mm2 to 16mm2 but retained the 25mm2 for connections from battery to inverter. 

In 2 weeks latter the same problem occurred again. I checked the internal resistance of the batteries 3 of those not replaced initially failed the test and also the readings of 2 the newly replace battery gave 15.3V and 16V respectively. This has really got me confused as to the cause of this continuous failure. I would be of utmost gratitude if a solution came up.

Regards
William

Comments

  • AguarancherAguarancher Solar Expert Posts: 312 ✭✭✭

    I take this is 2 banks of 12v batteries wired 4 ea. in series for 48v? If so and your standing battery voltage is 15.3 and 16V you have cooked them to death. Are these fla or what type of battery and who programmed your charge controller?



  • mcgivormcgivor Solar Expert Posts: 3,729 ✭✭✭✭✭✭
    What you are describing is a common problem in high temperatures, there are however many pieces missing from the puzzle.
    1. Are the batteries lead acid and if so are they flooded or sealed?
    2. Dose the charge controller have a remote temperature  sensor (RTS) to compensate for high battery temperature?
    3. How are the batteries configured, and where are the charge/discharge conductors connected?
    4. The load of  2000W is without a time factor, how many hours is the load powered?


    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • AguarancherAguarancher Solar Expert Posts: 312 ✭✭✭
    I am guessing this is his CC. It appears to have a BTS on the far left hand side but it's not stated in the specs?


  • BB.BB. Super Moderators, Administrators Posts: 31,452 admin
    William,

    While 36C is very warm for a Lead Acid battery bank (check the actual battery temperatures, especially when charging--During charging and equalization charging for a period of time, the batteries can exceed 45C or so--When charging is normally stopped until the bank cools).

    As the others have asked--Need to know more about the battery bank (6 volt or 12 volt @ 200 AH batteries or what?) for an XXX AH @ 48 volt battery bank.

    A 5,000 Watt AC inverter is pretty large--And a bit oversized for a 400 AH @ 48 volt battery bank (roughly a 2,000 to 4,000 Watt max inverter suggested).

    There is average power usage (Watts is a rate, like kilometers per hour) and total energy usage per day (Watt*Hours per day is an amount, like kilometers driven per day).

    For example, say you are in Lago Nigeria:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Lagos
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 84° angle from vertical (6 degrees from horizontal) :
    (For best year-round performance)

    JanFebMarAprMayJun
    5.80
     
    5.72
     
    5.34
     
    5.00
     
    4.71
     
    4.02
     
    JulAugSepOctNovDec
    3.91
     
    3.85
     
    3.91
     
    4.59
     
    5.32
     
    5.77
     

    3,600 Watt array...
    • 3,600 Watt array * 0.52 off grid solar eff * 3.91 hours of sun per day (September) = 7,320 Watt*Hours per day (Sept long term average)
    If you have a 2,000 Watt load, then in September, you would use your average daily harvest up in:
    • 7,320 WH per day / 2,000 Watt load = 3.7 hours
    Lets say you have an 800 AH @ 48 volt battery bank (4x 12 V @ 200 AH batteries in series, times 2 parallel strings). And you only discharged to 50% (for longer battery service life):
    • 800 AH * 48 volts * 0.50 max planned discharge = 19,200 WH of "usable" storage
    • 19,200 WH / 2,000 Watt load = 9.6 hours to take battery bank to 50% capacity
    And if you used the bank to 50% of capacity:
    • 19,200 WH (50% discharge) / 7,320 WH per day (Sept) = 2.6 days to recharge
    So--My first guess is that you are "deficit" charging... Not quite recharging the battery bank every day, so that after a while the battery bank eventually hits zero stored energy (like using water from a tank, and always refilling with a bit less water than was used the day before--Eventually the water tank will be emptied).

    The second guess is that the batteries were being recharged at too high of voltage, and they overheated multiple times/days/weeks (hot batteries, and/or lots of gassing/bubbling in cells during charging). The above members were asking about a "remote battery temperature sensor"... When lead acid batteries get hot, the charge controller is supposed to reduce the charging voltage to the battery bank. Basically, a 35C battery bank would be:
    • Assume 59.0 volts charging, 35C battery temperature
    • (35C temp - 25C room temperature) = 10C rise
    • 10C rise * 0.120 volts per degree C = -1.20 volts (for hot batteries)
    • 59.0 volts standard temperature charging voltage - 1.20 volt offset = 57.8 volts @ 35C actual charging voltage
    The third guess is, if these are flooded cell batteries, that the electrolyte level was not checked and the plates were exposed, and/or distilled water may not have been used to refill the batteries (water with minerals/stuff in it will damage batteries too).

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