I have a 1000wh unit with a Lithium Ion battery that was, through unforeseen circumstances, left in a vehicle at a temperature between 20 and 30 degrees fahrenheit for a period of about 6 days. No buttons work and the readout doesn't light up unless I plug it in, and then the readout says 0% among other things, but it's flashing so I don't know if that is a genuine 0% or just the panel flashing because it got too cold. It had 86% charge before it was left in the cold. Does cold cause the battery to drain to zero? Should I plug it in right away, or wait till it gets warmer (I've taken it inside and wrapped it in a heating pad on low)? Or does it not matter because it's basically fried?