Below are the American Solar Challenge regulations for the auxiliary (supplemental) battery:
8.2.C Supplemental Batteries
8.2.C.1
Supplemental, replaceable batteries carried in the solar car may be used to power: main power
switch, radios, commercially available electronic panel meters with internal batteries, cell phones, driver
ventilation fans (if solely used for driver ventilation), and the horn. Supplemental battery power may
be used to momentarily power the battery protection system (BPS) as defined by Reg. 8.3 to verify safe
battery parameters before energizing the main power switch. During a battery fault, in which the BPS has
automatically opened the main power switch, the supplemental battery power may be used to power the
battery fans per Reg. 8.4.D.
8.2.C.2
The supplemental battery used during start-up must also be used to power the BPS, BPS
Strobe, and BPS Fault Driver Indication under fault conditions. This supplemental battery must be
located in the battery enclosure.