Increase the capacity on Lead Acid batteries

Discussion in 'Power Electronics' started by kje, Apr 30, 2015.

  1. kje

    Thread Starter New Member

    May 6, 2012
    Hi, I have a few Lead Acid 55Ah 12V batteries holding it's voltage at 12.7V, but I've measured the capacity to about 20Ah. Is there a way to increase the capacity on these batteries?
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    simple answer is NO. Now you need to define how you came to the 20 AHr figure. Factory ratings are mostly "total depletion" points, or 11 volts or less under load for 12 volt battery. Discharges around 50%, which are considered normal and not deep discharge, make your 20 Ahr figure close to expected value
    Roderick Young likes this.
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Buy new or larger batteries.

    LA battery capacity decreases with time, especially if they are left undercharged, and over discharged, so just buying new ones of the same rating may be sufficient.

    If the original batteries are too small, buy ones with more Ah...
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    If not sealed make sure the water level is where it should be.

    If sealed or the level is fine then buy new ones.
    Roderick Young likes this.
  5. ian field

    AAC Fanatic!

    Oct 27, 2012
    Its also worth remembering that manufacturers quote the Ah capacity over something like 10 or 20 hour discharge rate.

    If you calculate a load to discharge a 55Ah battery in 1 hour - it'll be flat somewhat sooner.
    Roderick Young likes this.
  6. Ancel UnfetteredOne


    Jul 3, 2015
    Hhave you attempted to equalize the batteries and at least test the spec. gravity of the cells to see what's happening?
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    To get some extra life out of a battery, you can try this but it only works some times.

    Empty the battery, rinse/flush with distilled water, refill with new battery acid (sulfuric acid at correct concentration). Charge.

    If there is significant sulfated bridging or thick/hard sections of sulfate, or lead plates that are cracked or other damage, the battery has to be replaced.

    If the batteries are new and you just want to increase the capacity of your existing batter, you will not find an improvement for each individual battery. You can add capacity by adding more batteries in parallel.
    Roderick Young likes this.
  8. takao21203

    AAC Fanatic!

    Apr 28, 2012
    Once batteries have lost capacity, dump them, there will be more problems soon, total failure possibly.
  9. BokkieAndijk

    New Member

    Jan 7, 2016
    @GopherT I would like to make a small correction about your post. Please take a look at the next link: It looks like not a good idea to connect batterys parallel. Or am i wrong? Btw, sorry for my poor English.
  10. GopherT

    AAC Fanatic!

    Nov 23, 2012
    You should use a charge balancing circuit to insure that you do not under-charge one or more batteries in a series-parallel configuration.
    Dwarvensilver likes this.
  11. Dwarvensilver

    New Member

    Sep 9, 2010
    I tend to agree with GopherT.
    The article points the problem out and leaves it to you to figure out the rest so it is somewhat misleading.
    I don't think that because a magazine article states a problem that we are going to or should quit paralleling batteries, if the voltage is not what you want then ???
    Charge the bank correctly and maintain it well and it should serve for the expected life of your system.