Winter is coming: how do I protect the battery?

[6zfshdb]

My brother covers his bike & battery with an old twin bed size electric blanket. He covers that with another blanket to help hold the heat in. Set on low, it uses about 50 watts and only comes on when the temp drops below 40 degrees. Keeps the dust off as well.

I imagine you could do the same thing with a heating pad, since there's no reason to heat the whole bike. just wrap it around the battery case.