Battery charging problems
I have: 25 - 200W panels combined in 3 strings of 5 and 2 strings of 5 feeding two Xantrex XW - MPPT60 - 150 charge controllers. Inverter is Xantrex XW6048. This supplies 2 - 1380Ah GB forklift batteries - 48 volt (2x24v). Gen backup - 11,000 watt. All off grid in AZ max sun Country - 8 good hours at max every day at this time.
The background: The clown show that installed this got the array configuration wrong and by the time it was fixed the batteries were limping along at near total discharge. I knew once the generator backup came on I had a problem as it is set to come on at 43 volts.
The problem: The batteries drop to 47v overnight. The panels will bring the battery voltage up to float (53v) by about noon. But as soon as the sun sets thing start dropping quickly and I'm back to 48v by evening - 47 by morning. Here is the problem - no matter what the voltage says the batteries are clearly not taking a charge. s.g. is 1.15 and never rises. I do have power for the home at all times though (ave. - 1500w load)
The battery guy who is VERY knowledgeable says I went too long at this low voltage array setup before it got fixed for a new battery (six weeks old) and I'm not going to get them to charge till I get a good heavy equalization on them. OK but here's the rub, it takes till 2:00pm to get enough volt reading (56v for bulk/absorption setting) for it to trigger equalization and by then I'm headed towards the end of the days solar production so they never get a decent equalization which I believe to be about 4 hours. Somehow I must get out of this vicious circle and get a decent charge/equalization.
Possible solutions: 1. Set the absorb/bulk battery setting to something less than the 56 the tech says (say 52) so it triggers earlier and goes longer. 2. Run the generator to do the charge and equalization.
Some considerations and questions: re: #1, if I lower the bulk/absorption does the fact that the float voltage would then be lower than the bulk/absorb matter? re#2: the panel readout says the net to the batteries is around 120amps, is this too much to push to the batteries? There is a setting that says it won't push more than 60a so is this 120 that figure x 2? I'm sure there a many others but this is a start. Sorry for the book. I'm sure there is an answer - likely very simple that I'm just not seeing. Any thought would be appreciated.