From: Richard (metal@fullwave.com)
Date: Tue Mar 08 2005 - 07:53:46 PST
"" As a lead-acid battery goes from discharged to charged,
its internal resistance goes from low (allowing high current
to flow in) to high, as it approaches fully charged (limiting
the charging current) ""
That's not correct. It's actually the opposite of that.
A discharged battery has a HIGH internal resistance; which
gets LOWER as the battery charges. A very discharged
battery will NOT accept high charge-current.
When you try to push high currents into a flat battery, you
will see a very high voltage across the terminals (17-20 volts);
and the battery will get very hot inside because of the HIGH
internal resistance. That's one of the reasons they blow up
from improper jump-starts or fast-charging.
On a flat battery, you should limit the current to a level which
keeps the terminal voltage under 16 volts. As the battery
accepts some charge, you can start raising the current.
In any case, it is true that one can "trickle charge" a battery
pretty much continuously, so long as the current is limited
to a few amps. A group-31 size is probably safe at 5-10
amps; although this practice -will- cause loss of electrolyte
as the charging-hours add up...
Be sure to check the water level regularly.
A "ballast resistor" might work fine for current-limiting.
Multiple units could be put in series or parallel, or
series-parallel,
to achieve the proper resistance and wattage capacity at the
same time. Be careful where and how they're mounted, as
they do get quite hot at full power (50-100 watts each).
This archive was generated by hypermail 2.1.4 : Sat May 07 2005 - 20:41:22 PDT