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This strategy completely removes the need for an off state and ensures that the LV network will be inactive unless the driver has started the car. As a trade-off, it requires running another pair of wires up to the driver for the switch. It also requires modifying the fault logic of the supplemental BMS to differentiate between the disconnection of the supplemental battery to shut down the car and a low voltage fault. 

Follow-up

By WSC regulations, we plan on treating our supplemental battery as part of the energy storage system. This means that we are required to have active protection circuits and that it must live in one of the battery boxes. In addition, no conductors coming out can provide more than 50mA.

Thus, we plan on using a relay-based "primer" button located on the battery box to connect the supplemental battery to the rest of the LV system. This button will need to be pressed every time there the killswitch is pressed as well. This means that it is much easier to keep the supplemental battery-related circuitry within the battery box, so we will follow strategy A. We also plan on supporting the charging of our supplemental battery, most likely using NiMH for weight savings.