So, it’s well-known that lithium batteries lose capacity when temperatures drop well below freezing. However, since they generate some heat while discharging too, it seems logical that insulating the battery to retain this heat could help extend range in cold weather. My question is whether this makes a noticeable difference in real-world use?

I’ve been browsing eBay, but most covers seem to fall into two categories: uninsulated rain covers for external batteries or neoprene sleeves for built-in ones. My fatbike has an external battery, so I quickly jerryrigged a cover using a 20mm Armaflex sheet I had lying around. While it obviously didn’t hurt, I can’t say I noticed much improvement either.

Does anyone have long-term experience with insulating battery covers? I’d also appreciate recommendations for a good cover for external battery or tips on how to DIY one.