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.


-jim


y_p_w wrote:
>
> So here's the deal. The car is a Honda Civic with a group 51 battery
> (Kirkland Signature from Costco if that helps). Every once in a while
> the battery is heavily drained because a light (map light or headlamp)
> was left on. I do find it annoying that there is no headlight-on
> warning chime or auto-off. Sometimes it starts and sometimes it needs
> a jump; a portable jump starter always does the trick. The car itself
> is driven maybe a few times a month for short distances along with the
> occasional long trip.
>
> So I got a simple Schumacher Electric 1 amp, 12 V trickle charger -
> the kind with thin wires and light-duty clamps coming out of a wall-
> wart. It's labeled as a "manual charger" and the box/directions state
> that it's suitable for charging motorcycle and other small batteries,
> or for keeping auto batteries warm. I wasn't sure if I could justify
> getting anything more expensive like a higher output charger or maybe
> even a float charger/maintainer with a charge sensing mechanism.
>
> So I'm wondering how safe this is with a group 51 battery, which is on
> the small side for auto batteries? I realize that it's not likely to
> fully charge up a depleted battery unless it's on for days at a time.
> How safe is a 1 amp charge if uncontrolled like a float charger? I've
> heard some concerns that it could potentially overcharge - that maybe .
> 25 amp is about the limit for safe trickle charging. I've heard other
> comments that it's effectively a trickle charge that could safely be
> left on a fully charged car battery for days if not indefinitely.