How Calgary's extreme cold kills your car battery
Temperature and batteries have a nasty relationship — here's the physics:
When temperature drops below -20°C , a standard car battery loses roughly 50% of its cranking amps. Simultaneously, your engine's cold, thick oil requires up to twice the electrical power to turn over the starter motor. This double demand is exactly why Alberta winters kill aging batteries.
A battery that tested "okay" at an auto parts store in September often can't survive the first hard freeze of November. Rule of thumb: replace any battery over 3 years old before winter hits.