UPS battery bank ???

solarpowernovicesolarpowernovice Solar Expert Posts: 121 ✭✭
I found what I think is a good deal on batteries for my new battery bank but I am having trouble understanding the spec sheet. Here is the battery the guy is asking $1200 for 3 of them and that would give me a 48v battery bank. The problem is, I can't find a 20 hour rating anywhere on the spec sheet. Can anyone tell me what it is? How do I find out how to charge them and how many extra solar panels I need ect. ?

I also found some used solar panels for cheap but I'm not sure how to find out how old they are. Is there a way I can find out using a volt meter or how would I go about doing this? I would just take the guys word for it that they're 3 years old but you know how that goes...


  • EstragonEstragon Registered Users Posts: 1,920 ✭✭✭✭
    What is the intended application? These appear to be standby/UPS batteries - not well suited to any sort of deep cycle application.

    You can test panels for open circuit voltage voltage with a voltmeter. To test output, it's best to use a load and DC ammeter IMHO.
    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
  • solarpowernovicesolarpowernovice Solar Expert Posts: 121 ✭✭
    Thank you. I appreciate it.
  • BB.BB. Super Moderators Posts: 27,129 admin
    800 WPC (I think) and 232 lbs...

    WPC is Watt*Hour per Cell and used by UPS manufacturers (UPS are constant power devices and using Watt*Hour from full to empty for the battery bank (13 volts to 10.5 volts) is "more useful" than xxx AH at 12 volts nominal--Power=Volts*Amps, as volts go down, current draw goes up for UPS):'s-wrong-with-ah's-and-what-the-hell-is-watt-per-cell/

    OK, found a better link for specifications of your battery bank:

    Mfg seem to use WPC at a 15 minute discharge rate--A 20 hour discharge rate would have a higher apparent capacity. Assuming these are AGM type batteries, of good quality, and 15 minute discharge rate, comparing them to Sun Extenders/Concorde brand batteries (also high quality AGM):

    Using the specifications for an AGM battery scaled (by weight) to your batteries:

    Sun Extender/Concorde:
    Voltage 6 Volts
    BCI Group Size L16
    Ampere Hours @ 24 Hour Rate 405 Ah
    Weight 120 lb / 54.4 kg
    • 405 AH (SnX) * 232 lbs (EvrS) * 1/8 cells *  1/(120 lbs (SnX) * 1/6) = 587.5 AH @ 16 volts for EnerSys (est)

    Another sanity check, more or less, the AH per lb of lead acid batteries is very similar across manufacturers (lead + sulfuric acid + water--not much chemistry differences)...

     Voltage   6 Volts
    Series   4000
    Ampere Hours @ 20 Hour Rate   468 Ah
    Weight   125 lb / 57 kg
    • 468 AH per battery
    • 125 lbs per battery / 3 cells per battery = 41.6 lbs per cell
    • your battery is 232 lbs / 8 cells = 29 lbs per cell
    • 468 AH per cell (Rolls) * 29 lbs per cell (yours) / 41.6 lbs per cell (Rolls) = 362 AH per cell (estimated)
    Guessing that those batteries are around 362 to 587.5 AH range at 20 hour discharge rate... I would guess that 587.5 AH is too high of rating (wrong assumptions/guesses on my part).

    Comparing prices to other AGM batteries: $582 for 6 volts @ 405 AH (24 hour)

    Roughly: $582 * 8 cells * 1/3 cells for SunE = $1,552 per enersys battery (new equivalent 405 AH battery) $575

    A rough guess--New battery set for new AGM 48 volt @ 400 AH batteries is $4,656 (8x$582 Sun Extender 6 volt @ 400 AH AGM).

    So--Less expensive, but if you cannot find the cycle life (and aging life) of your battery bank, I would be unsure that these are "deep cycle" batteries with a cycle life of 10-100 cycles. A deep cycle 50% discharge cycle with Fullriver is spec'ed for 1,250 cycles or so.

    True UPS batteries in commercial data centers are usually replaced after 2 years or several deep cycles (power failures).
    Found more information:

    From the chart, it appears that that the math is 800 Watts into a load for 15 minutes... That would make the capacity 800 WH * 1/4 hours = 200 WH per cell at 15 minute (1/4 hour) rate... Or (roughly) 200 WH / 2 volts per cell = 100 AH @ 15 discharge capacity

    OK, found yet another document that we can calculate the AH rating directly:

    Battery Range Summary - EnerSys - EMEA (PDF)

    24 hours of constant current of 9.28 amps (24 hours * 9.28 amps) =  222.7 AH @ 24 hour capacity per battery.

    If that is the correct documentation, then much smaller (AH) battery than the 400 AH versions I compared it to (about 1/2 the AH rating).

    Still have not found anything on cycle (or aging) life yet.

    Here is the master link for the data sheets (best I could find):

    These batteries are for UPS applications and will not (probably) work well for off grid solar/deep cycle operation.

    DataSafe HX 16V Front Terminal Battery Installation & Maintenance Manual

    If they are fully charged, they can be stored (at room temperature) for upwards of 6 months between charging cycles. If the terminal voltage is less than 16.40 to 16.88 volts--Then it has probably been stored for over 6 months without charging and it scrap for your needs.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • solarpowernovicesolarpowernovice Solar Expert Posts: 121 ✭✭
    edited February 25 #5
    Very interesting stuff indeed. Thanks for your help once again Bill. You're the man!
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