Battery cell repair

adasadas Solar Expert Posts: 136 ✭✭✭✭✭
Aloha, I have a bad cell on one of my forklift batterys and I have another cell to change it with, but it is slightly smaller. As near as I can figure it the 12 cells in my 24v battery are all 2.1V @ 72AH each=875AH. The cell I want to install is a 2.1V 50AH. Since they are all the same voltage I should be able to add it into effectively a series connection? I can see the only drawback will be loss of capacity such as if I drain to 70% (on the 11 cells the smaller cell will be drained to 50%), roughly.

Do you see other problems?

frank

Comments

  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Re: Battery cell repair

    you will NOT be able to equalize that string, without severely boiling the small cell
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • adasadas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery cell repair

    Aloha, but any "bad thing" will only affect the small cell then? So if the small cell "crashes" after a period of time I would be able to replace it again with hopefully the correct cell. So nothing is lost except some time, as long as I do not ruin the remaining 11 cells? Any other downside?

    Frank
  • rplarryrplarry Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Battery cell repair

    Adas
    I'm a little confused about your battery bank. You say that you have 12-2v cells @ 72 ah each in sreies to make a bank of 24v @ 875 ah. When you connect batteries in series you increase the voltage only not the amp hours. So, if what you are saying is correct then you have a 24v bank at 72 amp hours, which seems awfully small for what you are doing with them.
    As Mike said, if you put a smaller battery in a bank of larger ones you will be over charging the small one. As your charger puts in amps in, the smaller one will fill before the larger ones and will overfill before the larger ones are full. Flooded lead acid batteries are pretty forgiving, so if you do add it to your bank, you will want to keep an eye on that cell and add water accordingly.
    Larry
  • adasadas Solar Expert Posts: 136 ✭✭✭✭✭
    Re: Battery cell repair

    Oh Oh i goofed. The batteries are 24V comprised of 12 cells @ 2.1 V (charged) each. The total amp/hr of the battery is 875AH. Each cell measures 5.75"x6"x29" tall and the one I will be adding is 5.25"x6"x29" tall.
    Actually I might be OK, as both batteries,- the old one with a bad cell is a 24v 875AH and the doner battery is a 36V 875 AH. Cells should be the same even thought they measure differently.

    These are industrial batteries (submarine, forklift, etc) and have strap connectors joining the cell. It is easy to change out the cells. Companies over here do it all the time.

    frank
  • mike95490mike95490 Solar Expert Posts: 9,572 ✭✭✭✭✭
    Re: Battery cell repair

    You've lost me, At the very least, charge the doner battery so the new cell is fully charged when you install it.

    And this a lesson about modular batteries. All those interconnects to bolt up at every cell.
    VS
    the expense of a entire new battery if a cell goes bad internally
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • rplarryrplarry Solar Expert Posts: 203 ✭✭✭✭✭
    Re: Battery cell repair

    adas

    Sounds like you should be OK with that replacement battery cell. Your bank sounds very much like mine. I use 6-2v cells each weighing 270 lbs. which gives me a 1600 ah 12v bank. The cells are connected with copper straps, and each cell has 2 pos posts and 2 neg posts. Mine are agm, so no need to check or replace water.
    Good luck with yours,
    Larry
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