I have a 2015 Volt. I use to get about 44 miles per charge, but I use to live in a warm climate. I've since moved to Portland, OR. I park it inside the garage & always keep it plugged in even after full. The temperature has been regularly in the mid to upper 30's at night & mid to upper 40's in the day. My range has been dropping regularly this past month & now the range is at 28 miles. The dealer is saying it's a normal drop due to cold. Is it normal to loose 16+ miles of range even with above freezing temps, kept in garage & kept plugged in?