12V-12V : DC-DC converters / Boosters

The DC-DC converters from 12 V to 12 V They do not change the voltage: they stabilise it. An alternator delivers between 12 and 15 V depending on engine speed, temperature and state of charge, and there are sensitive devices that require a constant voltage to function properly.

What is a 12V to 12V converter used for?

For two different things. Such as stabiliser, it supplies a clean and constant voltage to navigation, telecommunications and instrumentation equipment that cannot tolerate fluctuations from the alternator. As DC-DC booster or charger, it charges a second 12 V battery from the alternator using the correct charging curve, which is essential if the service battery is a lithium battery or if the vehicle is fitted with a Euro 6 smart alternator.

See also the battery combiners, the simple option when both batteries are lead-acid.