Plain-English definitions of the terms used across this site. Each entry is a page of its own, so it can be linked to and cited directly.
Where a term is contested — as with the standards — the definition says so rather than picking a side.
Terms
- Battery management system (BMS)
- Electronics inside a battery pack that monitor cell voltage, current and temperature and cut off charging or discharging outside safe limits. A pack without a functioning BMS, or…
- EN 14470-1
- A European standard specifying fire resistance requirements for safety storage cabinets for flammable liquids, classified by the time the contents stay below a defined temperature rise in an…
- Off-gassing
- The venting of flammable and toxic gases from a lithium-ion cell before or during thermal runaway. Off-gassing usually precedes visible flame, which is why gas detection can give…
- State of charge (SoC)
- How full a battery is, expressed as a percentage of its usable capacity. Cells held at a high state of charge for long periods age faster and store…
- Thermal runaway
- A self-sustaining reaction inside a lithium-ion cell in which heat generated by the cell drives further heat generation. Once it begins, the cell continues to heat and vent…
- VDMA 24994
- A German industry specification, published by the VDMA trade association, setting out safety requirements and test arrangements for cabinets used to store and charge lithium batteries. It tests…
- Watt-hour (Wh)
- The energy content of a battery, calculated as voltage multiplied by amp-hours. Watt-hours, not physical size or battery count, determine how much energy a cabinet may have to…
For the full comparison of the three standards quoted on cabinet datasheets, see EN 14470-1 vs VDMA 24994 vs UL 9540A.