Battery Question.

JBish130
JBish130 Registered Users Posts: 8 ✭✭
I'm using a Xantrex 6048 inverter with 4 Trojan 8D AGM batteries and a 7.5Kw generator. Everything is set on the SCP according to being "walked through" the setup procedure with an associate at Xantrex. It has worked great for about a month, but now I have a problem:

My battery bank isn't holding a proper charge. It runs down quickly but is back into absorption mode within about 10 minutes of starting up the generator.

So tonight I called my son (an EE) and asked him what could be wrong?

He told me that all he could do was guess, but that I could have a bad battery; and that I should check that first.

Ok, results: While my low voltage alarm on the SCP was doing its beeping thing, I checked the batteries individually for voltage and discovered that three of my batteries had 12.36v and one of them had 9.6v.

Here is my question: I suspect that I may have a bad battery, in fact I'm pretty sure of it. Is there anything else that could pull down the voltage that low in 1 battery? Should I suspect any other problem that could have caused this?

As I pointed out above, my system is configured correctly for the generator, inverter, and the batteries; at least as far as the guy at Schneider instructed (and I went through all the settings while on the phone, it was an actual "walk-through").

I want to make sure I correct the problem instead of "fixing" a symptom. I will be making telephone calls tomorrow to both Schneider and Trojan.

Anything anyone can tell me, any advice at all, would be greatly appreciated.

Thank you.

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Re: Battery Question.

    Battery does not sound good... AGM batteries are bit more difficult to diagnose (cannot measure Specific Gravity).

    230 AH batteries? A bit on the small side for a 6kW 48 volt based inverter.

    What is the size of the solar array (wattage)?

    What is the average charging voltage you have seen? Is it closer to 56.8 volts or 59.2 volts (or higher)? AGMs are sensitive to over charging (too high of voltage and too long of absorb time).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • softdown
    softdown Solar Expert Posts: 3,812 ✭✭✭✭
    Re: Battery Question.

    Sounds like a bad battery is pulling down your bank. Hopefully you can still return it under warranty. I agree with BB that your battery bank is possibly small for your inverter. 8D's? I have used 8D's for four years and heard many things. They generally do not enjoy a strong following in the solar community. One person hyped them as "deep cycle" but I have doubts. If they are not deep cycle, it behooves the owner to keep them over 12.3 volts I think.

    I severely damaged some 8D's by letting them down to 10.5 volts for a couple days while I was away. The alpacas kept the building security lights on and drained the batteries in cloudy weather. Then I likely overcharged them with a 40 amp charger left on for too long. They were pretty much junk within 4 days. Partially re-susicated them with a two week de-sulfation procedure on the grid.

    There are so many ways to damage a battery bank. It is frightening considering their immense expense.
    First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
  • sub3marathonman
    sub3marathonman Solar Expert Posts: 300 ✭✭✭
    softdown wrote: »
    Re: Battery Question.

    I severely damaged some 8D's by letting them down to 10.5 volts for a couple days while I was away. The alpacas kept the building security lights on and drained the batteries in cloudy weather.
    There are so many ways to damage a battery bank. It is frightening considering their immense expense.

    Don't you just hate it when the alpacas do that? :grr

    But, on a more serious note, it is highly suspect that the batteries are much, much too small for the XW6048. Read posts from Solar Guppy, or visit his (mostly inactive but still readable) website. Don't feel too bad, its happened to many, including me. Mostly because the literature stated, and maybe still does, that the XW6048 needs a minimum of 100ah batteries to operate. Well, technically that's true, but in reality the ripple current (I had to learn about that too) will get the batteries too, especially if they are that small. The "rule" is 100ah of batteries for every 1kw of PV solar for the XW6048.