My RV has two batteries separated with diodes. One for the motor, and one for RV power. The alternator charges both through the diodes, but the discharged battery on the RV side doesn't load the main motor battery.
The peltier module draws 3 amps at 12 volts, and makes 150 btus of thermal transfer. I made a solid state AC unit with 4 modules, that is still running 7 years later. About 150 watts for 600 btus.
Stay safe, and pet that fur boy!
🤠💙🐕🐾🐾