Batteries getting a bit weak

adasadas Solar Expert Posts: 136 ✭✭✭✭✭
Aloha, I have 2 systems running, (Shop and Office). Using large old forklift batteries, some of the batteries are getting weak. I got lucky when I got the forklift batteries for free. 4 of the 24V are still running strong at full charge of 25.4, but the 4 36V ones that are tapped off at 24V are only going up to 24.7 on "full charge". (batteries are bubbling and getting warm, I forget what hydrometer reading is). There is no bad cell. most are even at 2.05v each. So it looks like I have some weak batteries that may last 1 week or one year.

Question is can I tap off the batterys at 26V and set the FX80's at say 28.8 bulk? (inverter likes 29v max) So, I will add another cell and the inverter will not be grabbing a lot more amps when it has to convert to 110vac from 23-24V and will be getting 26.8v to convert to 110VAC? Will I realize more performance above and beyond just adding another 8% overall amperage?


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Batteries getting a bit weak

    If you've got 36 volt batteries and are only taping them at 24 volts that'd be a long-term problem: some fo the cells aren't getting used (?). They probably need(ed) to be equalized across the whole 36 volts.
    Mixing battery types/voltages is a sure-fire way to kill some of them prematurely.
  • adasadas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Batteries getting a bit weak

    Aloha, Since the batteries were free from a salvage yard and I had to revive them with 2-3 gallons of water and in a state of charge of about 20V instead of 36v, I feel they have remarkabley come back to life. The 18 cells in the 36v battery are totally separate and only joined on top by a lead bar. A couple of the batteries had a dead cell so I merely jumped over the cell, (cut the strap) so have five cell left. if/when a couple more cells go bad I will have five cells left to use. I keep the remaining unused cells trickle charged. These batteries are very rugged and made to run dead flat (although not recommended) in electric forklifts by operators wanting to finish off the last 20 minutes of their shift work on an almost dead battery. In fact electric lifts are designed to shut off lifting function and limp into the charging station under their own power. I had a couple of 24v lift batteries that were in the corner since 1993 and tested at 5v. I since charged and eq'ed them and they are working fine now holding a charge. But your post reminds me that i need to EQ the batteries in question as I do not have a EQ circuit. (my inverter is max 29V so I will need to assign a FX80 to branch off and set up for a 30-31v EQ function. We use 30KWH per day and have not used the Genny since March, so hopefully will make it through the rainy season here in Hawaii. 2-3 days of total overcast is about all these batteries will handle.
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