12v dual energy storage system

Section 15.2 discusses multiple drivers to supplement the lead–acid battery in the power-supply system with an additional ESD. A dual storage system can improve the vehicle's performance, fuel economy, electrical capabilities, or overall robustness depending on the system's implementation.

One option to guarantee the electrical power availability is a redundancy in the power-supply system. Dual energy storage systems can play an important role to fulfil these requirements. The major target here is to have more than one source to supply power over a defined time period.

Dual battery 12-V topology for voltage sensitive loads. The major difference when compared with the topology in Section 17.3.2 is the operation of the switch. It will be closed during recuperation and when the auxiliary energy storage is not capable of supplying the sensitive loads.

The OCV of the ESD is inherent to its fundamental chemistry. Therefore, technology selection for the auxiliary storage device must be considered early in the design process of a dual battery system. Absolute voltage limits and the shape of the voltage curves over SoC should be well understood.

For example, even in a dual battery system, the main lead–acid battery will remain in a narrow SoC window, similar to its operation in a conventional power-supply system. This is limited by carry-over functions like cold cranking and quiescent drain, as well as the achievable typical SoC.

Depending on the topology, it may be possible to simply remove the battery from the system by operation of a switch if the system approaches a condition outside of the battery's intended operating envelope. The functional safety classification for the second ESD is dependent on what vehicle systems the battery is supporting.