Active interconnection of batteries

Number of Students : 1 or 2
Guides : Umanand L

Almost all EVs in the world have battery packs containing several hundreds of cells in series and parallel combination. In most cases, the packs are composed of series cells called strings which are connected in parallel with just copper connection. This leads to large local circulating currents that goes undetected by current sensors placed external to the pack. Even during “parked” conditions when there is no external current flowing from the battery packs, there will be local internal circulating currents flowing non-stop. Over time, this will cause deterioration of some of the cells and can cause thermal runaway. In order to prevent this, active paralleling techniques must be employed. This project proposes to incorporate such active paralleling techniques such that any eutectic combination of batteries or sources may be connected in parallel without any local circulating currents.
Further, the series connection of batteries need charge equalisation circuits. Most present battery packs use resistive or dissipative equalisation circuits. This project will implement active charge equalisation along with active paralleling mechanism.