How to find the right battery size for your car

The fastest way is to read the label on your current battery, if it's the original or a correct replacement. Look for the group size, a number like 24F, 35, 48 (H6), 65 or 94R. Also note the type (AGM or flooded) and the cold cranking amps. If the label is gone or you don't trust the last install, use the owner's manual or give us the year, make, model and engine.

Group size

The Battery Council International group size is a standard code for the physical case: length, width, height and where the terminals sit. A group 48 battery is the same box shape no matter who makes it. Some groups go by more than one name. Group 48 is also called H6, and 94R is also H7, for example.

Why it matters:

• Too big and it won't fit the tray or the hold-down won't close.
• Too small and it can move around. A loose battery vibrates, which damages it, and can short against the hood or body.
• Terminals on the wrong side and the cables won't reach, or they'll be stretched tight, which is a short-circuit risk.

The "R" in sizes like 24R or 94R means the terminals are reversed compared with the base size. That small letter matters.

CCA, cold cranking amps

CCA is how much current the battery can deliver at 0°F for 30 seconds without dropping too far in voltage. It's a measure of starting power. In Tampa it's almost never 0°F, but CCA is still a useful comparison of strength.

Rule: meet or beat the car's spec. More CCA than required is fine. Less is a mistake, especially for bigger engines and diesels.

Reserve capacity

Reserve capacity is how many minutes the battery can run basic loads if the alternator quits. Higher is better, especially for cars with lots of electronics, and for start-stop cars where the battery runs things while the engine is off.

Type

Group size and CCA aren't enough on their own. You also need the right type: standard flooded, EFB or AGM. A car that came with AGM needs AGM, even if a flooded battery in the same group size would physically fit. AGM vs. flooded.

Where to look

1. The battery label. Fastest, as long as the battery is the right one.
2. The owner's manual. Usually in the specifications section.
3. The door jamb or under-hood labels. Some cars list it.
4. A parts lookup by year, make, model and engine. These are usually right, but watch for trims with different batteries.

Many cars have more than one possible battery depending on engine, options or region. A truck with a towing package might have a bigger battery than the same truck without it.

Where the battery lives

Not every battery is under the hood. Some are in the trunk, under the rear seat, under the passenger floor or behind a panel in the cargo area. Those often have a vent tube that has to be reconnected, which is another reason AGM is common in those spots. If yours is hidden, tell us when you call so we plan for it.

Trucks with two batteries

Diesel trucks and some heavy-duty gas trucks have two batteries. They should be the same size, type and age. Replace them as a pair. Truck and SUV batteries.

Hybrids

Hybrids have a big high-voltage pack and a small 12-volt battery. The 12-volt is often an unusual size and sometimes in the trunk. Hybrid 12-volt batteries.

If the last battery was wrong

It happens. Someone put in what they had on the shelf. Signs of a wrong fit: a hold-down that doesn't quite grab, cables stretched to reach, a battery that sits low or high in the tray, or the wrong type for a start-stop car.

When we come out, we check what your car is supposed to have, not just what's in it. If the last battery was wrong, we'll tell you.

What to tell us

Year, make, model, engine size, and whether it has start-stop. A photo of the current battery label helps too. That way we load the correct battery before we drive out. See warranties and date codes for what else the label can tell you.