Li Ion batteries

1865 / 18650 cells

Diameter is 18 mm and length 65.0 mm.

Voltage

Note that the chemistry changes and thus these value might be a bit different. Be careful.

• Discharge cutoff voltage (the low voltage limit) is around 2.0V to 2.5V
  • Over discharged < 2.5 V
  • Discharged 3 V
• Nominal voltage is (usual) 3.6 V or 3.7 V.
• Full charge voltage is 4.2 V, which is the maximum voltage

Chemistry:

• Lithium Cobalt Oxide (LiCoO2): nominal voltage of 3.6V and is known for its high energy density.
• Lithium Manganese Oxide (LiMn2O4): a nominal voltage of 3.7V and offer thermal stability compared to LiCoO2
• Lithium Nickel Manganese Cobalt Oxide (NMC): a nominal voltage of 3.6V or 3.7V and provide a good balance of energy density and power capability.
• Lithium Iron Phosphate (LiFePO4): a nominal voltage of about 3.2V with excellent safety characteristics and long cycle life.

Over the upper limit (maximum voltage) battery will cause electrolyte breakdown and thermal runaway.

Below the lower Limit the battery’s chemistry may change irreversibly.

State of charge (SOC) and maximum voltage relation.

Charging

The standard charging voltage for most 18650 Li-ion batteries is 4.20 V ± 0.05 V. But slight charge and discharge will improve the battery reliablity and life cycles.