48V Battery Pack for Mild Hybrid Applications

Mild hybrid vehicles employing 48V systems are expected to achieve significant growth in most major automotive markets in the near future. A 48V architecture brings a number of significant technical benefits to the vehicle and the battery itself will be much smaller, lighter and lower cost than high voltage alternatives.

Analysis of a typical C-segment vehicle, driving on the new WLTP legislative cycle, suggests that the majority of available braking energy can be recovered using a battery with peak charging power of 20 kW. MAHLE Powertrain’s new, in-house designed 48V battery pack has been conceived to provide repeated charging and discharging at these high power rates to maximise the potential for energy recuperation during deceleration and braking events.

The selected cell chemistry (LTO) enables a service life of more than 20,000 cycles before the battery capacity drops below 80% of its original value, and also ensures very good resistance to thermal runaway. A high efficiency yet simple cooling system has also been integrated into the pack to maintain the cell temperature within its optimum range (<55 °C) and the bus bar was carefully designed to prevent additional heat input into the cell terminals.

This compact battery pack will offer significant opportunities for 48V mild hybridisation and is capable of supporting any MHEV architecture from P0 to P4. An optimised battery management strategy will ensure that the operating points remain in high efficiency areas during WLTP and RDE testing and fuel economy benefits of up to 15% will be achievable when applied in a P4 hybrid configuration in a C-segment vehicle.