JW> Steven beat me to it. Yes, a small electrified blanket that warms the
 JW> battery when it is plugged in. Batteries loose half their cranking power
 JW> every 10 degrees C and cars won't start when its colder than -40 without
 JW> the blanket even if the block heater is on.

I have never heard about this although I live in a "winter" country myself.
If my battery would need a blanket I would change it. I believe modern cars
are so easy to start, only a couple turns are enough, even at -30 C and a
block heater
makes it even more easy and makes the metal in the cylinders not to "rise".
A cold start at -20 C wears out the motor just as much as 50 km warm driving
and think about all that gas the motor requires to start at - 20 C when all
cold start
equipment just are pumping in gas that's only passing through without beeing
burnt.
IMO a block heater is more than 10 times better then a battery blanket.

//Bj”rn

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