Battery knowledge · Modules, packs and battery management

Auxiliary battery

The small 12 V or 48 V battery in an electric vehicle that powers the controllers, lights and locks and wakes the BMS, kept charged from the high-voltage pack through a DC/DC converter. A flat auxiliary battery immobilises the car however full the main pack is.

Also called
12 V battery, low-voltage battery

Example

Modules, packs and battery management: an example situation

Twelve 3.6 V, 5 Ah cells in 6s2p give 21.6 V, 10 Ah and 216 Wh nominally before other restrictions.

Read Auxiliary battery alongside DC/DC converter in this context. The power electronics that step the high-voltage pack down to 12 V or 48 V for the auxiliary systems, replacing the alternator of a combustion car. Boost converters also appear between an 800 V pack and a 400 V charger.

Use in Lemonergy

Make series/parallel architecture explicit.

This is a reference concept. No executable Lemonergy block has been verified for this term.

References & further reading

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

  1. Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification

    Gregory L. Plett · Journal of Power Sources · 2004

    Topic background · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.

  2. Getting Started with the BQ76925

    Texas Instruments · 2019

    Topic background · A concrete BMS analog front-end example: cell voltage, current, temperature measurement and MCU integration.