Lead-acid
| Bulk | Constant current (C/5 to C/10) until ~14.4 V (12 V pack) |
|---|---|
| Absorption | Constant voltage at 14.4 V until current tapers to C/50 |
| Float | 13.6 – 13.8 V continuous maintenance |
| Equalize | Periodic 15.5 V burst for flooded cells (not AGM/gel) |
NiMH / NiCd
| Slow | C/10 for 14–16 h — no termination needed |
|---|---|
| Fast | 0.5C – 1C with termination: −ΔV (NiCd ~5 mV/cell drop) or +ΔT/Δt (NiMH temp rise) |
| Trickle | C/50 – C/30 for maintenance |
Li-ion / LiPo (CC/CV)
| Phase 1 (CC) | Constant current at 0.5C – 1C until cell hits 4.2 V (or 3.65 V for LiFePO₄) |
|---|---|
| Phase 2 (CV) | Hold voltage, current drops. Terminate when current < C/20 – C/10 |
| Precharge | If cell < 2.8 V, trickle at C/10 until normal range |
| Never | Exceed 4.25 V/cell. Disconnect if cell < 2.5 V. Do not charge below 0 °C (plating). |
Modern fast-charge
- Multi-step CC: step current down as voltage rises — faster than CC/CV alone.
- Pulse charging: brief rest intervals reduce internal heating; disputed benefit.
- USB PD / PPS: phone and supply negotiate fine-grained voltage matching battery, skipping buck stage.
- Cell balancing (BMS): bleeds off hot cells or shunts charge — essential in multi-cell Li packs.
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