Cal. Code Regs. tit. 13 § 1248
Every storage battery on a motor vehicle first sold and registered after January 1, 1967, unless located in the engine compartment, shall be protected by a substantial and securely fastened enclosure or removable cover. Battery compartments and all adjacent metal parts subject to corrosion from battery leakage shall be finished with an acid-resistant substance, and the compartments shall be vented to provide adequate battery ventilation and drainage. Cables passing through a metal compartment to the starting motor shall be insulated against grounding by acidproof and waterproof bushings. When both the battery and the fuel tank are installed under the driver's seat, they shall be separated by a partition, and each compartment shall be provided with independent covering, ventilation, and drainage.
Cal. Code Regs. Tit. 13, § 1248