You bring up a great point. The battery spec is only given at -10C. That's a mild normal day's low temperature in winter in Minneapolis, USA. But it's often muc

You bring up a great point. The battery spec is only given at -10C. That's a mild normal day's low temperature in winter in Minneapolis, USA. But it's often much colder than that for long periods of time. I wonder if this glassy layer they apply can handle -30C; a temp where above ground heat pumps are no better than electrical resistive heating.