PulseTechSolarPulse SP-7 Solar Battery Charger Maintainer

I have a four battery system in my semi truck. The cold weather here puts a drain on batteries. Will this unit maintain batteries?

I have a new travel trailer with 2 Interstate srm 27 batteries wired in parallel. What's the wattage I need to keep them charged during the winter?

after 2 1/2 years just noticed red light is not working on the controller,does this mean it's dead ?

Can I us 7 watts plusetech on 2 12 volt at the same time