Bank Charging

Bank charging is where we split the pack in two to charge it. Thus an 800V drive pack becomes two 400V packs in parallel for charging.

Porsche Macan battery pack electronics

Porsche Macan PPE

If the station is using 400-volt technology, the all-electric Macan uses ‘bank charging’ for the first time, whereby corresponding high-voltage switches (gates) are automatically switched in the battery before the actual charging process begins. This effectively splits the 800-volt battery into two batteries with a nominal voltage of 400 volts each that can be charged in parallel on one 400-volt charging station without an additional HV booster. If necessary, the states of charge of the two battery halves are first aligned before they are charged together.

A split pack means you essentially have two battery packs and thus: 2x BMS, 2x fuses, 2x contactors, 2x current sensors. Thus adding cost, complexity and more failure modes.

Also, splitting the pack and moving from a series connection at 800V to the two packs arranged in parallel means the two packs have to be very close in terms of overall voltage, probably <15V difference. This is achievable when the packs are new, but could become more difficult as the packs age.

Is this better than fitting a DC-DC to the vehicle to allow 400V charging when needed?