Kat's 22200 80W Battery Thermal Wrap Review

A lead-acid battery at 0°F delivers roughly a third less cranking power than at 80°F; at -20°F it's closer to half. Meanwhile the engine needs up to twice as much current to turn over through oil that's thickened to syrup. That's why the coldest morning of the year is when a marginal battery gives up — and it's why a battery blanket is the single cheapest cold-start aid for a car that lives outside in real cold country.

Kat's 22200 is the standard one. It's an 80-watt heating element in a 36-inch wrap that goes around the battery case and cinches with a strap. Plug it into an outdoor-rated extension cord; better, put it on a timer so it comes on two or three hours before you leave. The battery stays at a temperature where it delivers nearly its full rated amps, and the car starts the way it did in October. At 80 watts the electricity cost is negligible.

Be realistic about what it does and doesn't do. It warms the battery — not the oil, not the block. A four-cylinder with a healthy battery and the right oil weight will usually start fine at -20°F with just the blanket. A V8 or a diesel at that temperature wants an engine heater too (Kat's makes magnetic and block heaters for exactly this). And it needs an outlet: if you park on the street, the answer is a jump starter in the cabin and a fresh battery, not a blanket. For the driveway-parked car in the cold half of the country, it's $30 that prevents a lot of mornings you'd rather not have.