On 06/04/2018 15:24, whisky-dave wrote:
On Friday, 6 April 2018 15:05:34 UTC+1, Dave Plowman (News) wrote:
In article ,
newshound wrote:
Going slightly OT, pulled an apparently dead 105 AH leisure battery out
of a caravan yesterday (hadn't been used for months and the charging
circuit claimed it was dead when on mains hookup).

Gave it best part of a pint of demin water and stuck it on charge on a
traditional charger, this morning all the cells are bubbling nicely and
it's showing over 14 volts immediately after disconnection. Will stick
it on a smart charger for a few days but I'm quite hopeful.

Sadly, voltage is no real check for a lead acid. You need to measure its
capacity in amp.hrs. No real point in keeping a thumping great 100
amp.hr battery if it's well down.

I thought the only way to estimate the charge in a lead acid cell was to test it Specific gravity or similar with a hydrometer, well this is what I was told at school when given the job of charging their lead acid cells for physicas experiments.


SG is an indicator of the state of charge, not necessarily so reliable
in an old battery which may have been abused.