DESIGN IDEAS Linear Charger for Nickel Cadmium
or Nickel Metal Hydride Batteries
by Fran Hoffart
Minimizes Parts Count
Introduction A Primer on Charging
NiCd/NiMH Batteries The various methods for charging
Nickel based batteries are categorized
by speed: slow, quick and fast. The
simplest type of charger is a slow
charger, which applies a timer-controlled, relatively low charge current
for about 14 hours. This may be too
long for many portable applications.
For shorter charge times, quick and
fast chargers apply a constant current
while monitoring the battery voltage
and/or temperature to determine
when to terminate or stop the charge
cycle. Charge times typically range
anywhere from 3 to 4 hours (quick
charge) to around 0.75–1.5 hours
(fast charge).
Fast and quick chargers force a
constant charge current and allow …