|Battery Application & Technology
Constant-current charging simply means that
the charger supplies a relatively uniform current,
regardless of the battery state of charge or temperature.
Constant-current charging helps eliminate imbalances of
cells and batteries connected in series. Single-rate,
constant-current chargers are most appropriate for cyclic
operation where a battery is often required to obtain a full
charge overnight. At these high rates of charge there will
be some venting of gases. Positive grid oxidation will occur
at elevated temperatures or extended overcharge times.
Normally the user of a cyclic application is instructed to
remove the battery from a single-rate, constant-current
charger within a period of time that permits full charge yet
prevents excessive grid oxidation.
Another type of constant-current charger is
the split-rate charger. A split-rate charger applies a high
initial current to the cell and then switches to a low rate
based on time of charge, voltage, or both. The choice of
switching method and switch point may be affected by the
relative priority of minimizing venting (early switching)
versus maintaining good cell balance (later switching). In
some split rate chargers, the charger will alternate between
the high and low rate as the battery approaches full charge.
Split-rate chargers are useful when the discharge cannot be
classified as float or cyclic, but lies somewhere between
the two applications.