On Jun 24, 1:32*pm, jim <"sjedgingN0Sp"@m@mwt,net> wrote:
> A 1 amp charger can be left on for a couple days and in fact a very slow
> charge is the best way to revive a completely discharged battery.
> Contrary to what many people believe, completely discharging a lead acid
> battery doesn't do much harm. Mostly, *the damage is done when
> recharging it. I think you are looking at something like 3 days to
> charge a fully discharged battery with 1 amp.

When I use a portable jump starter I typically leave it on for a
minute or so before disconnecting it. It should definitely charge up
the jump starter's battery a bit, and I understand that it might also
reduce the initial charging current to the car's battery. I've been
told by some people that a lower initial charging current is critical
to reduce battery capacity loss.