Battery Chargers and Jump Starters: Choosing the Right One
A charger restores and maintains a battery; a jump starter gets a stranded engine running. Here is how to tell which you need, and how to size and specify each.
Decide: charger or jump starter?
A charger replenishes a battery slowly and safely and can keep it topped up for weeks. A jump starter delivers a short burst of current to start an engine with a flat battery. Many workshops need both.
Match voltage and chemistry
Choose a charger for the system voltage you service, such as 6, 12 or 24 V, and make sure it has modes for the battery types you handle: lead-acid, AGM, gel or lithium.
Pro tip: Never charge a lithium battery with a lead-acid-only charger.
Pick the right charge current
As a rule of thumb, a charge current of about 10 percent of the battery's capacity is a good balance. A 50 Ah battery on a 5 A charger takes roughly ten hours to recover from flat.
Look for smart features
Multi-stage charging, temperature compensation, a maintenance mode and reverse-polarity protection protect both the battery and the user. A supply mode that holds vehicle memory settings is useful during battery changes.
Size the jump starter to the largest engine
Peak current matters most with large diesel engines and in cold weather. Check the manufacturer's guidance, and choose a unit with headroom for the biggest vehicle you will meet.
Pro tip: Keep jump starters charged: a flat unit is no help on the day you need it.
Related questions
What do the Ah and A numbers mean?
Ah is the capacity: how much energy the battery stores. The A figure is the cold cranking current: how much power it can deliver to start the engine. Match or slightly exceed the original specification, and make sure the terminal layout and dimensions fit.
How do I choose between AGM, EFB and standard batteries?
Vehicles with start-stop systems normally need an AGM or EFB battery, while older vehicles without start-stop usually use a standard flooded battery. Check the vehicle handbook and read our buying guide for a step-by-step check.