80 watts on a timer keeps the battery warm enough to crank like it's October. Cheapest cold-start insurance there is.
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~$30 typical price
Buy on AmazonUse-case guide · 2026
Best winter car gear for Extreme Cold (−20°F and Below)
At -20°F the rules change. Batteries deliver half their power, oil turns to syrup, rubber seals freeze, fuel can gel, and the margin for a roadside wait goes from uncomfortable to life-threatening in under an hour. The prep list for real cold is about heat — for the battery, the engine, and the people — and about a jump starter that's been kept warm enough to do its job.
What extreme cold actually needs
Battery at −20°F
~50% of warm cranking power
Must-haves
Battery blanket or engine heater, 2,000A+ pack kept in the cabin, wool blanket
- ▸A plugged-in battery blanket (and for big engines, a block or pan heater) on a timer for 2–3 hours before departure is the standard in cold country. Outdoor-parked cars need it most.
- ▸A lithium jump starter at -20°F has lost real capacity. Keep it inside the cabin — better, bring it indoors overnight — and buy one class bigger than the engine needs.
- ▸Synthetic oil in the weight the manual specifies for cold (often 0W-20 or 5W-30) dramatically cuts cranking load.
- ▸Frostbite on exposed skin happens in minutes with wind. The kit isn't optional: wool blanket, mylar, hand warmers, hat, gloves, and a charged phone.
Not sure what else you need? Build your personalized winter checklist →
Our picks
2. NOCO Boost HD GB70
9.2
/ 10
Headroom is the point in deep cold: a 2,000A pack that's been kept warm starts a cold V6 or V8 when a 1,000A one hesitates. Diesels: GBX155.
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~$200 typical price
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3. CTEK MXS 5.0
9.0
/ 10
The cold/AGM mode raises voltage for sub-freezing charging so a battery in an outdoor-parked car actually reaches full.
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~$100 typical price
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Wool insulates when damp and won't melt near a candle or heater. Pair it with mylar and hand warmers.
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~$59 typical price
Buy on AmazonBefore you buy
- ▸Diesel fuel gels in deep cold; treat the tank with anti-gel before it happens, not after.
- ▸Don't run the engine for heat with the tailpipe in a snowbank — clear it first. CO poisoning in stalled cars is a real winter killer.
- ▸Tire pressure: a tire set to 35 PSI at 60°F is around 27 PSI at -20°F. Check it.
Frequently asked questions
Do lithium jump starters work at -20°F?
They work, but at reduced output — lithium chemistry loses capacity as it gets cold, and NOCO rates its packs to -4°F. The fix is to keep the pack in the cabin or bring it indoors overnight, and to buy a size up (2,000A for a V6, 4,000A-class for a diesel) for margin.
Battery blanket or block heater?
A battery blanket warms the battery so it delivers its rated amps; a block or oil-pan heater warms the engine so it's easier to turn. Four-cylinders with a good battery usually need only the blanket; V8s and diesels at -20°F and below want both, on the same outdoor timer.