The low voltage (12V) battery (LV Battery) is located in the right part of the rear boot/trunk/baggage compartment and it is of smaller dimensions and charge capacity than those found on conventional drivetrain cars.
This is due to the fact that the LV battery is fed, after the "Ready" mode status is enabled, via a step-down DCDC converter from the High Voltage, high capacity battery and its main purpose is to turn on the computers of the Prius.
Subsystems fed from the LV Battery are:
- Electric Power Steering (EPS)
- Water pump
- Radio/Navigation System
- Brake pump
The oil pump is mechanically driven from the internal combustion engine (ICE), while the A/C compressor is linked directly to the high voltage battery. The brake pump is connected to an additional capacitor bank.
Because of the number of systems connected to the 12V network, and the smaller capacity of the 12V battery (whose main purpose is to start the computers managing the HSD) it is not advisable to use the accessory mode for long periods. For example, it is advisable to listen to the radio for longer periods of time, by keeping the Prius in P(ark) while in Ready mode, to allow the HV battery to feed the 12V network via the DCDC converter (and if necessary start the ICE to re-charge the HV battery).
The Prius can be jumped started in case the LV battery is discharged, by connecting another 12V battery to a dedicated contact available inside the engine bay.