Battery Basics
Battery chemistries compared — voltage, energy density, cycle life, and safety notes.
Reference
Common chemistries
| Chemistry | Cell V nominal | Energy (Wh/kg) | Cycles | Notes |
|---|---|---|---|---|
| Alkaline (Zn-MnO₂) | 1.5 | ~100 | 1 (primary) | Disposable; self-discharge low |
| Lithium primary (Li-MnO₂) | 3.0 | ~280 | 1 (primary) | Coin cells, long shelf life |
| Lead-acid (flooded) | 2.0 | 30–50 | 300–500 | Cheap, tolerates abuse |
| Lead-acid (AGM) | 2.0 | 40–60 | 500–1 200 | Maintenance-free |
| NiCd | 1.2 | 45–80 | 1 000 | Memory effect; cadmium toxic |
| NiMH | 1.2 | 60–120 | 500–1 000 | Self-discharge (LSD variants better) |
| Li-ion (NMC) | 3.7 | 150–250 | 500–1 500 | Phone / laptop workhorse |
| Li-ion (LCO) | 3.7 | 150–240 | 500 | Old phone chemistry; thermal risk |
| LiFePO₄ | 3.2 | 90–160 | 2 000–5 000 | Safer, longer life, lower density |
| Li-Po | 3.7 | 100–265 | 300–500 | Flexible form factor |
| Lithium-Sulfur | 2.2 | 400+ | ~200 | Research — high density, low cycles |
| Solid-state (EV) | ~3.7 | 250–450 | 1 000+ | Emerging — safer, energy-dense |
Series / parallel basics
- Series (×N)
- Voltage adds; capacity (Ah) unchanged
- Parallel (×N)
- Capacity (Ah) adds; voltage unchanged
- Match cells
- Series packs must be balanced — use BMS for Li-ion
Notes
- Lithium packs REQUIRE a BMS — cells can go into thermal runaway if over-charged, over-discharged, or shorted.
- State of Charge (SoC) estimated by voltage is only rough — coulomb counting is more accurate.
- Self-discharge rates: Lead 2–5%/mo, NiMH 1–2%/mo (modern LSD), Li-ion ~2%/mo, LiFePO₄ <3%/mo.
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