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(no email)
Date: Tue Dec 02 2003 - 22:43:49 EST
OOooo - that makes my electrolyte boil - its time that myth was put to
sleep, and double shame on Calder if he did say that. This is one of the
most common fairy tales I face on a daily basis. I should be directing my
service calls to Calder to answer if he is responsible for creating this
bloody mess.
OK, pay attention.
The charge level of a battery is characterized by the terminal voltage.
A terminal voltage of 14.2 volts would typically represent FULL CHARGE.
Battery chargers/regulators are designed to limit voltage to this level.
Any thing less than that is less than full charge.
Any thing over that is some degree of "overcharging".
So how the hell are you going to overcharge the "little" battery while
undercharging the "big" one when they are in parallel?
If they are in parallel they are at the SAME VOLTAGE.
When the little one gets to 14.2 volts, the big one must be at 14.2 volts
too.
It doesn't matter what the size, what the chemistry or how they are charged,
if they are in parallel they are at the same voltage and consequently at the
same level of charge, undercharge or overcharge.
You can't overcharge the little one without overcharging the big one.
OK?
Now that does raise the question of current distribution between the
batteries. Since it is current (amp hours) that charges a battery, how does
the little battery know to take just its share of the current and leave the
remainder for the big one? This is the question that is causing the
confusion and the question you should be asking. For a more technical
description of how this works, read this section of our Combiner FAQ at
http://www.yandina.com/combInfo.htm#Q32
Andina Foster,
>SNIP
>
>
> I have often heard, and Calder mentions a couple of times, that
paralleling
> unlike battery banks (ie, a small starting battery and a large bank of
deep
> cycle batteries) will likely result in overcharging the smaller battery
> and/or undercharging the house bank. It seems that this would be the case
> regardless of how you go about paralleling the banks. I suppose the
problem
> is even worse when you parallel gel cells and flooded cells together.
>
>
>
> If the starting battery is almost fully charged and a large house bank 50%
> discharged, when you parallel them and place a charging current in the
> circuit, it seems to me the starting battery would be fully charged long
> before the house bank, and would then bubble away unnecessarily for the
> whole time the house bank is charging. If this doesn't happen, why doesn't
> it?
>
>
>
> I am going to do a little direct observation on this over the next couple
of
> days. I'll wear goggles while I watch 'em bubble.
>
>
>
> Jack
>
> sadly not boating
>
> Minneapolis
>
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