Believe stator puts out about 340 watts at 5000rpm but only about 120 watts at idle. Typically low at idle.
Running the bike would be around 90 watts or so.
As long as you are moving most of the time the battery should stay charged.
Not sure if there was improved stator outputs in later years so check your owners manual.
If it is that cold consider the heaviest duty battery you can fit.
C30F Power Up needle
2 turns out
Baffle out, Screens In
It starts,it runs,it gets to where all CRFs can get to without the valve or valve plate dramas