These batterys "don't charge when cold", per Niterider. You have to warm them up to ~70 degrees yourself before attaching them to the charger. I just got one and wondered how many others are miffed about this? The thing doesn't even warm up during discharge. So, I'm left between a typical morning ride and the shower, work and those other sort of time critical things, sitting there for 10-15 minutes with it in my pocket (their suggestion) before plugging it in for the magic red light, indicating its charging. Otherwise, it sits no matter where you put it, with a blue led that flashes red (fault code not described in the manual). Charging won't start until you plug the battery in warm. Period.
Maybe I should just cut all of my morning rides an extra 15 minutes short?
I'd let it sit inside my house, perhaps on its own pillow, before plugging it in at night, but who here hasn't forgotten to charge a bike light right after a ride, let alone when they get home from work?