The battery charge is a function of ambient temperature. When the temperature goes down, so does the available charge. A race to the bottom in bad weather.
The absence of a hardcopy manual may be an indication that they don't know how to write one. (See cell phones.)
If the battery decides to catch on fire, the vehicle and anything within about 10 feet will become a total loss. Think about that when you park your car for the night. (Powered by thermite.)
Additionally...
Its a race to the bottom in hot weather as well. The battery charge degrades faster in temps over 85F.