Will my WFCO 55 amp over charge?

The WFCO is perfectly fine to float a lead-acid battery in the cold of winter. If still concerned check the battery voltage after a week of no use to see you are in the 13.2 to 13.6 range.

Bring batteries in and keep them warm. They like that.

Don’t know how well a solar would work here in the frozen short sun lite days of the north.

Get a 10 or 15 watt 12v solar maintainer and hook to battery. Disconnect the negative wire and turn off your converter.. Your battery will thank you

A thirty watt solar panel with a decent controller will do the job much better. Still need to check battery water level every month however.

I would not.