Dave Plowman (News) wrote:

What voltage was needed to pass 1 amp? This tends to be the clue. A
heavily sulphated lead acid can have a very high internal resistance so
most modern chargers can't pass enough current. Same as trying to charge
it with the car alternator after a jump start.


I'll check that when I disconnect the charger for the night later
today. It can't be much more than 12v, because the max of this supply
is 12v. Which reminds me, as the battery comes up to voltage, the
charger won't do the trick anymore. I'll have to get a real car battery
charger.

Leave the lab supply set at one amp on for about 3 days.


It seemed to be common sense to trickle charge it for awhile, instead of
jolting it with a jump from a charged battery. Beyond common sense, is
there a reason for a low 1 amp charge for several days? Is it to
prevent hydrogen formation?