Battery charging schemes and most effective

Battery charging schemes differ in how current and voltage are controlled during charging.

1. Constant-current charging – current fixed at about C/10. Purpose: first charge of new batteries, accurate restoring of known Ah; used in battery workshops.
2. Constant-voltage charging – fixed voltage ≈ 2.3–2.4 V/cell; current falls as battery charges. Purpose: fast, self-limiting charging, e.g. vehicle alternator charging.
3. Trickle charging – tiny continuous current equal to self-discharge. Purpose: keep idle standby batteries (emergency lights, alarms, DG starting) always full.
4. Float charging – charger, battery and load in parallel at ≈ 2.2 V/cell. Purpose: no-break DC supply in substations, telecom and UPS; battery takes load at mains failure.
5. Boost charging – high current for a short time. Purpose: quick recovery of a deeply discharged battery.
6. Equalising charge – periodic controlled overcharge. Purpose: equalise voltages and specific gravity of all cells in a string.

Most effective method: the modified constant-voltage (CC–CV) method – constant current at first, then constant voltage, then float. It charges fast without overcharging or excessive gassing and gives the longest battery life, so it is used in most modern chargers. For standby duty, float charging is the most effective in practice.