Have a good controller that won't re-set and go into auto equalize etc.. I would also reduce the absorption voltage if you can to 14.2V or lower as you will be hitting batteries that are not self discharging rapidly, or at all, with an absorption voltage every day. With most controllers, they re-set at night and start the charge cycle all over... It is also a good idea to have a controller that draws very little in standby so if the panels become occluded with snow etc. the controller won't drain the batteries..

Panels, even very small ones, without a controller, can easily cook batteries during the winter when left with no loads on them and little self discharge. When they get full there is simply no place for the excess current to go so the voltage just climbs...