rumor has it that LT wrote:
> Yes, I know the correct answer is "Battery Tender" -- it is on my Christmas
> wish list.
>
> But here is my question. Is there any significant damage done by leaving a
> normal battery charger on overnight, where it might get to zero amps but
> stay attached for a few hours? This is not a fancy battery charger that
> shuts off or kicks into trickle mode or such.
>
> I did leave it on overnight routinely last winter with no apparent damage,
> but am curious about the long term impact of doing this. We're talking in my
> case one of the Interstate Battery mega-mothers under the hood, not a cheap
> off-brand battery.
The danger to a batter changing battery is either heat or overchange.
Car batteries are built such that heat during charge is not really a
issue, so the only thing left for us to worry about is over-changing.
And it so happens that is easy to test. Take a DC voltmeter and measure
the voltage at the battery when the charger is reporting zero amps.
Because of Ohm's law, when there is no current flowing into the
battery, the battery matches the changers voltage.
13.8 volts is max for an "old fashioned" add-water battery.
14.4 volts is max for a maintanence-free battery.
The damage will be more the greater the voltage and the longer it's
exposed. That means 14.5 V won't do much damage unless it's left
that way for weeks or months.
Philip, armed with a digital meter
