Joel W. asked:
>>
Sorry, what does "float charge" mean?
<<
To keep your batteries ready to use at any time you leave them on charge
permanently: "floating".
To do this, and not kill the battery, you need to limit the current to a safe
low value where the
cell does not overheat or vent etc. Some batteries like Lead Acid for example,
can be floated for
many years without damage with a suitable temperature compensated float voltage
(they
automatically self limit charge if you regulate voltage). When I was a student
the EE department
had a lab where they had a battery room so you could pipe in 100's of volts to
run the fields
large DC motors at up to 1000A. The batteries had been on float for about
30years old and still
worked just fine.
For NiCd's most vendors specify that their cells can be floated at say C/10
current for 1 year
with a loss of capacity of 50r so. This is not a recomendation, but just that
if you happen to
leave them on charge, with a cheap C/10 charger, they will survive the abuse!
Although they
survive the abuse their life may still be reduced longer term, due to
heating,seperator
damage,seal compression leading to leakage etc. NimH will lose capacity if
charged more than
~1200f C each cycle. So float charging, *if* recommended by vendor, requires
very low currents.
One automatic method sometimes used in place of a low float current, is to
allow self discharge
and then just trigger a smart recharge cycle periodically.
Regards,
Tim Hughes
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