Car Battery Chargers and Starter-Chargers: 6/12/24 V

A charger only restores the battery charge, while a starter-charger can also deliver a large short burst of current to start an engine with a flat battery. Switch-mode units are light and compact, while transformer units are heavier but robust and suit intensive workshop use. Use the start mode in short cycles with rest breaks — see what is the PV or ED duty-cycle rating.

Make sure the unit supports your battery type — conventional flooded, AGM, GEL or EFB — as each needs a different end-of-charge voltage. Automatic chargers charge in stages, switch to maintenance mode and may offer desulphation and winter modes. Learn more: lead-acid battery types (AGM, GEL, EFB) and charging modes.

Most passenger cars use a 12 V battery, motorcycles and older machinery sometimes 6 V, while trucks, buses and special vehicles use a 24 V system. If you service different vehicles, choose a model with several voltage modes. On voltage: volt (V).

As a rule, charging current is set at about 10 % of battery capacity — for example, about 6 A for a 60 Ah battery — and the unit’s maximum current and recommended capacity range should match your batteries. Read how to choose charging current by battery capacity; on current: what is electric current (A).

Reverse-polarity, short-circuit, overcharge and overheating protection matter, as they protect the battery, the unit and the vehicle electronics. See what is motor thermal protection.

Check the length and cross-section of the leads and clamps, especially on starter-chargers where the current is very high, as well as the mains cord length. If you need an extension cord, use one with a suitable cross-section: how to use an extension cord safely.

A digital display or ammeter shows charging progress, and a housing protected against moisture and dust matters in garages and workshops. On protection ratings: what is an IP rating; on proper storage: how to store power tools correctly.

Batteries can release hydrogen while charging, so charge in a well-ventilated place away from flames and sparks. Connect the clamps to the battery first and only then plug the unit into the mains, and disconnect in reverse order. Read how to charge a car battery safely, essential power tool safety rules and essential fire safety rules.