charging external 12v battery with accessory port

[Ducky's Dad]

I have a 100 ah deep-cycle lead-acid battery that will run a Dometic 65.

I'm running an Indel B 50 on a pair of Optima Blue 34M house batteries, at 55ah each, so total 110ah. In desert summer conditions, I get less than 24 hours before they drop below 50% SOC, unless I recharge them. Truck normally gets driven a couple of hours per day on those trips with a 270amp alternator and that is barely enough to keep up with the drain. I'm going to add a 100W solar panel and quit worrying about the batteries.

 

[TwinStick]

Ducky's Dad,

What type of solar are you looking at ? And how many watts/amps do you think I would need for an 82 qt & a 50 qt ARB ? Each would have it's own 12v deep cycle battery.