Simple Question - Bet the Answer is Complicated

CBear42
CBear42 Solar Expert Posts: 28 ✭
in Off Grid Solar & Battery Systems #1
Hi all,

I am the unfortunate who ran into an unscrupulous installer - who advised me to discharge my batteries until the Outback Inverter light hit "red". Turns out that means that my 24v system was sitting at 23v or below - which translates to something like a 80-85% depth of discharge! Fortunately, in his answering the BBB complaint I filed, he stressed how he TOLD me to "let the light go red repeatedly" before charging the batteries.

But, I have a question - apparently, despite the fact that he fraudulently obtained the installation job and lied about his credentials...I need to be able to show damage before I can haul him into Small Claims Court. My question is:

I have 4 sealed, AGM 12v 250Amp batteries. How do I actually TELL if these batteries have been damaged? I know that length of life is shortened with repeated deep discharges - but how can I PROVE the current state or what they should be at this point (4 months old)? It's not like I want them damaged! But, if they are, I need to be able to prove it somehow. Waiting until they die early isn't an option because he could always claim that I abused them somehow in the interim.

Any ideas anyone?

Thanks in advance for all the brilliant help you guys always give!

CBear
· Share on Twitter

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Simple Question - Bet the Answer is Complicated

    How many times did this deep discharge happen?

    The good news is that 23 Volts under load is not as bad as 23 Volts at rest. The batteries probably are not damaged per se; perhaps some time has been shaved from their life potential.

    Proving it would be difficult, because you don't have any "new" reference to compare their state to now. You could, at best, perform a controlled load testing if you had the equipment. Not many people or even battery dealers have this equipment.

    If the discharge was consistent you could show 'X' hours at 'Y' Amps when new and now a significantly lower hours' usage at the same current.

    This is probably not worth pursuing, as the difficulty in proving your case is great and the likely remuneration small.
    · Share on Twitter
  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Simple Question - Bet the Answer is Complicated

    You have a 24 bolt @ 500 AH battery bank... Concorde, for example, defines end of life when the battery will not support 80% of its rated storage capacity...

    In your case, recharge the bank fully, let it sit over night (at least--to make sure no self discharge). Then discharge it at a 20 Hour rate:
    • 500 AH * 1/20 hour rate = 25 Amp @ 24 VDC 20 Hour rate
    • 24 volts * 500 AH * 1/20 hour rate * 0.85 inverter eff = 531 Watt AC load for 18 hours

    So--If you have ~500 watt electric heater or 5x100+ watt filament lamps that run on the 120 VAC inverter--And your batteries support that for ~18+ hours--Then the battery bank is "still good".

    If the bank dies sooner, then you may be able to claim the bank needs replacement (if the bank only supports 17 hours--might be a tough call--If the bank dies in 10 hours, lots easier.

    Otherwise, you might ask your battery supplier (or a local distributor that is not connected with your installer) to independently test the batteries and write up a report for you as a warranty claim (you could do two at a time if you need power for your home).

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

Categories