CCA: what the number actually means
CCA (Cold Cranking Amps) is the current the battery can deliver for 30 seconds at −18 °C while holding above 7.2 V. Higher is better, but the OEM-specified minimum on your owner's manual is what the engine actually needs — adding more CCA doesn't damage anything, it just gives headroom for the coldest mornings.
Practical sizing for Canadian use
- GTA / Lower Mainland (mild): OEM minimum is fine, ±10 %.
- Prairies / Northern Ontario (regular −25 to −35 °C): 15-20 % above OEM minimum is sensible.
- Yukon / NWT / northern Quebec (regular −40 °C): 25-30 % above OEM, plus a battery blanket or block heater on the coldest nights.
AGM vs flooded in cold
AGM holds a higher resting voltage and recovers from deep discharge better — meaningful for a vehicle that sits for a week at an airport in February. Flooded is fine for a daily driver. The CCA rating tells you cranking performance; AGM gives you cold-storage tolerance, which is a different property.
Keeping it healthy through winter
Short trips kill batteries faster than long drives in cold — the alternator never fully recharges what cranking pulled out. If your daily drive is under 15 minutes, plug into a smart trickle charger overnight once a week. Battery blankets help on −30 °C nights; block heaters help even more (warmer oil = easier cranking = less battery drain).
If your battery is more than 3 winters old, get it load-tested in October. A battery that starts your car at 5 °C may not at −25 °C, and the first time you find out is at the worst possible moment.