I like riding a bike. And, of course, I use battery powered devices (a mobile phone, GPS tracker, headlight, etc.) But the problem is that regular li-ion batteries don't work well in the cold. That's why I decided to make a LiFePO4 powerbank, which is supposed to perform better at low temperatures.
ZIPPY Flightmax LiFePO4 6.6V 2500mAh 5C
DC-DC step-down buck converter: 5–40V to 5V 2A USB