What you need is a volt meter, a good quality digital is nice but not
necessary, and a battery charger with a predicted output, ie, amp meter.
When a battery is above 13.2 volts, it is fully charged. When it is below
11 volts it is discharged. As batteries deteriorate, the amount of total
energy that can be stored decreases. So, looking at the voltage of a
battery is like looking at your fuel guage, it tell how full it is in
relative terms, but you don't know the size of the tank because it is
changing over time (getting smaller). Number of amps multiplied by the time
that it is being charged tells you how much energy is stored in the batter
(how big your gas tank would be)
So, if your battery reads 11.5 volts it is discharged. If you charge it
with a 15 amp charger and it charges in a couple of hours (13.2 volts or
higher), it's pretty marginal. Charges in 6 hours, it's pretty good.
Charges in 5 minutes, toast.
Discharging a battery battery by normal means is not harmful. What is
harmful is to let a battery sit discharged at or below 12 volts because it
sulfates. So draining a new battery by starting your car should do the
battery no harm as long as it gets recharged right away.
I give this schpeel in the neighbood all the time while I help people out
with their dead battaries but when I read the above explanation which I just
wrote, I'm not sure that anyone can follow it.
Chris DeStaffany
1966 Herald since 1971 doing a frame off
Son of an electronic engineer who got this lecture from his dad for years!
>
> While we're on the subject of batteries I have another question.
>
> I have a battery the hasn't been used since Oct 96. I also have a
>battery
charger, and a Volt/Amp meter. How should I test the battery to judge it
current state? If I connect the battery to the charger, is it possible to
use the meter to judge how much chargine is required, while the charger is
attached to the battery?
>
> I know I will by a new battery soon, However I just put the engine back
>in
the car, and I would just like to see the starter turn over so I know
everything is wired correctly? I would also like to start the car once
before I buy a new battery. I don't want to drain a new battery doing this
if I don't have to.
>
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