Each battery chemistry has its own general charging needs, and different
battery construction within a battery chemistry can modify those needs.
I general NiCd batteries can be slow charged with constant current; most
popular types can be charged indefinitely with a current equal to their
capacity divided by 10 hours (i.e., a 2000mAh battery can be charged at
20mA). This is mostly OK, but will lead to slow drying of the
electrolyte.
Some NiCd batteries can be quick charged, particularly if you've got a
charger that will watch the battery voltage as it dumps in current, and
terminate the charge cycle when the battery voltage peaks then starts
dropping.
Lead acid batteries need a charge regime where both the maximum voltage
applied to the battery and the maximum current are limited. Even with the
voltage limit, you have to cut the charge off at some point or risk drying
out the battery. If the battery is designed for it you can 'float charge'
a lead acid battery almost indefinitely, but the 'float charge' voltage is
less than the 'fast charge' voltage. Moreover, the correct charge voltage
limit varies with the temperature of the battery -- which can be different
from ambient, if the battery is being charged or discharged rapidly.
NiMH batteries are similar to NiCd, but more delicate.
LiPo batteries are similar to lead-acid, but more prone to damage, and far
more prone to bursting into flame if they get seriously cranky.
Etc. Hopefully you get the idea.
Do research, dig, get a copy of "Rechargeable Batteries Application
Handbook" (
http://www.powells.com/partner/30696/biblio/9780750670067) for
background, read it, dig some more.
If you find a book that's more up to date than the one above, please let
me know.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at
http://www.wescottdesign.com/actfes/actfes.html