1. Trickle-charge If the battery voltage is below a
predetermined threshold, indicative of a very
deep discharge or one or more shorted cells, a
small trickle current is applied to bring the
battery voltage up to a level corresponding to
near zero capacity (typically 1.7V/cell@ 25
degrees C). Trickle charging at low battery
voltages prevents the charger from delivering
high currents into a short as well as reducing
excessive out-gassing when a shorted cell is
present. Note that as battery voltage increases,
detection of a shorted cell becomes more
difficult.
2. Bulk-charge Once the trickle-charge threshold
is exceeded the charger transitions into the
bulk-charge state. During this time full current is
delivered to the battery and the majority of its
capacity is restored.
3. Over-charge Controlled over charging follows
bulk-charging to restore full capacity in a
minimum amount of time. The over-charge
voltage is dependent on the bulk-charge rate as
illustrated by figure 1. Note that on unsealed
batteries minimal over-charging should be