Lithium battery hazards
Battery types in a typical turboprop electrical system (AFH): lead-acid, nickel-cadmium (NiCad), lithium-ion.
Lithium hazards: high energy content, potential thermal instability (AC 20-184 1.3.1, 1.4.2).
- Failure often causes thermal runaway: self-sustaining, uncontrolled increase in pressure and temperature (TC AC 700-065 (f)).
- Runaway often ends in fire: vented flammable gases ignite. Unburned gases can be toxic (TC AC 700-065 (d)).
- Significantly more susceptible than nickel-cadmium or lead-acid to internal cell failures causing runaway.
Stated causes and effects:
| Cause | Effect |
|---|---|
| Over-heating | Can go into thermal runaway and fire (TC AC 700-020, 6.1 (4)(f)) |
| Overcharging | Heats and destabilizes cells; electrolyte can ignite |
| Over-discharging (some types) | Corrodes electrodes; permanent capacity loss |
| Internal defects | Internal short; may not show until long after installation |
| Flammable electrolyte (some types) | Fuels external fire if a cell fails |
| Extreme temperature | Major hazards unless within manufacturer's specification |
Trap: thermal runaway is a self-sustaining temperature and pressure rise with fire and toxic gas, not simple loss of charge; lithium is more susceptible than nickel-cadmium or lead-acid.
References
- FAA AC 20-184 (Rechargeable Lithium Battery Systems on Aircraft), 1.3.1, 1.4.2
- TC AC 700-020, 6.1 (4)(f) (battery over-heat may lead to thermal runaway and battery fire)
- TC AC 700-065 (d) and (f) (high energy fire, thermal runaway)
- FAA-H-8083-3 Airplane Flying Handbook, turboprop electrical system (battery types)