How do I keep a car battery from dying if the car is not used often?

A battery maintainer (also called a trickle charger or battery tender) provides a continuous low-level charge to keep the battery topped up without overcharging it.

Running the engine allows the alternator to recharge the battery, counteracting self-discharge and parasitic drain.

Disconnecting the battery physically isolates it from the car's electrical system, stopping parasitic drain from components like clocks, alarms, and computers.