Quick answer
The main ratings on a car battery are cold cranking amps (CCA), which describe starting power in the cold, reserve capacity (RC), which describes how long it can run basic loads, and sometimes amp hours (Ah), which describe stored capacity. Size is a separate matter: the group size sets the case dimensions, terminal positions and hold-down fit. For a replacement, match the group size and terminal layout your vehicle needs, and choose a CCA rating that meets or exceeds the manufacturer’s recommendation.
Car battery ratings explained
Cold cranking amps (CCA)
CCA is the standard measure of starting ability in cold conditions. It is generally defined as the current a battery can deliver for 30 seconds at 0 degrees F (about minus 18 degrees C) while staying above a minimum voltage per cell (7.2 volts for a 12V battery). A higher CCA number means more cold-start capability, all else equal. It matters most in cold climates.
Cranking amps (CA)
CA, sometimes marked MCA, uses a similar test at 32 degrees F (0 degrees C). Because warmer conditions are easier on a battery, CA is normally higher than CCA for the same battery.
Reserve capacity (RC)
RC is the number of minutes a fully charged battery can supply a steady 25 amps before dropping to about 10.5 volts. It gives a rough idea of how long the battery could carry essential loads if the charging system failed. Higher is generally better.
Amp hours (Ah)
Ah describes how much charge a battery stores, usually quoted over a set discharge period. It is more commonly shown on European-style batteries and deep-cycle batteries. A 70Ah battery stores more energy than a 60Ah one, so in principle it can supply a given load for longer.
60Ah versus 70Ah
A larger Ah figure means more stored energy, but it is not the only thing that matters. A physically larger battery may not fit your tray, and starting power is shown by CCA (or the EN equivalent), not Ah. Use the capacity and starting-power figures recommended for your vehicle, and avoid fitting a size that your car’s hold-down or cable reach cannot accommodate.
Group size and fit
In North America, battery group size (set by BCI) is a code that defines the case length, width and height and also the terminal layout. Two batteries with similar ratings may still not fit if the group size differs. Check three things:
- Dimensions: Make sure the case fits the tray and the hold-down secures it.
- Terminal position and polarity: The positive terminal must sit on the correct side so cables reach without strain.
- Height and clearance: Taller batteries can touch the hood or heat shielding.
In Europe and elsewhere you will see other codes and standards, so check the manufacturer’s information for your region.
How to find the right size
- Look at the label or tray of the battery currently in the car.
- Check the owner’s manual for the group size and recommended CCA.
- Use a retailer’s vehicle lookup, and confirm against what you see under the hood.
- If your car has start-stop or a lot of electronics, confirm the required battery type. See car battery types compared.
Reading the date code
Many batteries carry a date code, either a sticker or a stamp, showing when the battery was shipped or made. Formats vary by brand, and some use a letter for the month and a digit for the year. Check the manufacturer’s explanation for your brand. Choosing a fresher battery helps avoid one that has sat on a shelf and lost charge.
Is a higher CCA better?
A rating above the minimum is generally fine as long as the battery fits, and can help in cold weather. Going below the manufacturer’s recommended CCA is more likely to cause starting problems. Paying much more for far higher CCA than you need often gives little extra benefit in mild climates.
Frequently asked questions
Can a car battery be overcharged?
Yes. Too high a charging voltage, from a faulty regulator or an unsuitable charger, can damage a battery. A running voltage far above the usual range is worth getting checked. See car battery voltage for typical readings.
Do brand tiers such as Gold and Platinum differ?
Retailers often sell several tiers of the same brand that differ in warranty, CCA and construction. Compare the printed specifications and warranty terms for the exact models rather than relying on the tier name.
Does size affect weight?
Yes, larger cases hold more lead and usually weigh more. See how much a car battery weighs.