BoatBanter.com - View Single Post

On 24 May 2004 16:14:56 GMT, (Gould 0738) wrote:

It may have been charged at 13.2, to 13.2, or whatever you want to call
it. But if you're taking the measurement right after charging, you're
reading an artificially high voltage.

No, there's nothing "artificial" about it.
That's the voltage reading at the time a battery finishes charging. As others
have said, (quoting various time periods from
"almost right away" to "overnight") the voltage eventually drops to a lower
point.

If you've got a $3000 paycheck, spend $200 on the way home from work and only
have $2800 with which to pay your bills, would that mean that you *never* had
$3000?

Actually, that's not quite the way to think about it because you're
assuming something got spent. The way to think about it is, you got a
paycheck, you don't spend any and take it home. A few hours later look
at it and it says it's worth $2800. You can spend that $2800 or let it
sit under your mattress where inflation will mean that it's worth 3%
less every month (self discharge). It doesn't matter that it said $3000
when it was given to you a few hours earlier because the penalty for
spending even a single dollar is that it immediately becomes worth only
$2799. That's because even though the battery may read 13.2 volts
immediately after charging, it won't have hardly any more capacity then
it does after it settles.

If you put the battery to work as soon as it has recharged to full capacity and
before it undergoes the internal changes that lower the voltage, you can take
advantage of (some of) the additional voltage.

No, not really. There are only a fixed number of moles of molecules
available to be converted to electric power. If you put it to work as
soon as it has recharged and is still at 13.2 volts, by the time it
reaches say a 90% charge, you won't get measurably more power out of it
then if you waited a few hours.

A battery that cannot be brought to a point above 12.6 when charging,
considering the benefits of the internal heat and the concentration of
chemicals on the plates,

You can bring a battery to as high as you want when charging. You can
charge it at 100 volts and measure that across the terminals. There
will be current flowing with the battery acting as a resister. It won't
last long though. It will probably boil off so much flammable gas and
get so hot that it'll explode. But that doesn't mean you can't get 100
volts to appear across the terminals beforhand.

is not in good shape. What would happen to the battery that barely charges to
12.6?
It will also cool down, the chemicals will also equalize, etc.......leaving you
with
what? 12.1? 12.2?

If we are going to apply the "battery cools down and chemicals equalize after
charging" caveat to the battery charged to
2.2 volts per cell, it must also be applied to
batteries charged to only 2.1.

It applies to everything. But the problem is that now you're looking at
a battery that is not in good shape. Big lead sulfate crystals may have
formed that can't be broken down by normal charging. They may have even
broken loose from the lead plate and settled on the bottom of the
battery. That locks up some of the sulfate which would be converted
into sulfuric acid when charging and so the concentration of sulfuric
acid in the electrolyte never gets very high. It also takes away some
of the sponge lead on the plate that's available to be converted into
lead sulfate when discharging, reducing the capacity of the battery.

This is a different case again then looking at the settling voltage of a
fully charged battery in good condition.

Steve