I found this interesting site called Polar Power about the technological hurdles of providing power to sensors deployed in polar (i.e. cold) regions.
Interestingly, although Li ion batteries provide almost double the energy density in cold weather when compared to lead-acid batteries, they are not often used in systems that have recharging capabilities (solar or wind). It is not clear to me exactly why, but I think the charging requirements for them may require higher current than can be delivered by standard power systems.
It seems like this could be handled with a charge controller
that charges by pulses resulting from discharge of a
capacitor.