20amp 12v lead acid battery overcharging ?

Discussion in 'General Electronics Chat' started by MeGuinness, Mar 17, 2015.

  1. MeGuinness

    Thread Starter New Member

    Mar 17, 2015
    hello, wondering if you guys can help me,
    i have a 2x identical 12v 20amp lead acid batteries , one of them due to been left in the garage unattended for about 2 years had a voltage output of about 1V ,i know practically dead,anyway in trying to salvage it before go and buy a new one i decided to top it up with some deionised water and put it on charge using a RC charger in Pb mode .
    Due to the low voltage the charger would not start the charge.
    After some thinking ....I connected the good and the dead battery together in series and left them for one hour.. .....once I removed the connections the dead battery voltage was up to about 12.40V ,so I quickly connected the charger and yes it started charging no problem. I put the settings at 0.5amp charging .

    Now the fist battery was still at 12v and using the same charger i had no problem in fully charge it ,the charger did put about 6000mah and stopped when it was time to.

    My problem is with the second so called dead battery ,yes i managed to start the charge but the charger will not stop charging even after putting in about 28000mah in it and a voltage of 13,20V.
    If the battery is rated at 20amp how is that the battery could take 28000mah??? what is wrong ?is it overcharging ?
    i left the battery off the charger for a day and when i checked the voltage is at 12.46V .
    Any ideas ?thanx
    [​IMG] [​IMG]
  2. tcmtech

    Well-Known Member

    Nov 4, 2013
    First off recharging a battery is not the same as charging up a capacitor so be expecting considerable ah discrepancies between the batteries AH rating and how many AH go into recharging it.

    Basically regenerating a near flat dead battery takes a lot more charge than just what its AH rating is.

    Personally if it was me when I try to regenerate dead batteries I try to hold them at around 14.4 volts give or take a few 10ths for a good day or two before concerning myself with what their amp draw is or what their voltage stays at.