Thread: Battery Meter
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Eisboch
 
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Default Battery Meter


"Jeff Morris" wrote in message
...

A bad battery or a depleted battery may still read a high voltage when

connected
to a charger, and even for a while after being removed. All your reading

of
13.2 tells you is that your charger decided to go into float mode. This

may be
a strong hint that the battery is fully charged, but it doesn't

necessarily mean
that.


Exactly. The best way to tell (other than checking specific gravity of the
cells) is to also monitor the charger current delivered to the battery. If
it is at it's float voltage (13.2v - 13.5v) and is still indicating a small
current flow, then the battery voltage - which is a reflection of it's
apparent internal resistance - is less than the float voltage. A difference
of potential must exist in order for current to flow. If the battery charge
potential were the same as the charger float potential, the current meter
would read zero.

With due respect, I think this is where Gould's understanding is flawed.
The battery behaves like a variable resistance as it is charged, much like a
large capacitor. For a given charge voltage delivered by the charger, the
current will vary (decrease) as it is charged).

Not to start this debate all over again, but I think Gould might be
surprised that while his voltage meter is reading the float potential of the
charger, it is almost a certainty that there is still a small amount of
current flow - probably an amp or 2. This can only mean that the battery
has not come up to 13.2 volts.

Eisboch