Effective solar battery tender

   
I have been using  2  of these for a combined 7 Watt total output going on 4 months now with great results, using the cigarette lighter plugs  connected  to both sockets. No more dead starter battery after sitting for a month in storage
 https://www.menards.com/main/electrical/generators-alternative-power-generation/solar-power/coleman-reg-3-5-watt-12-volt-solar-charger-panel/58104/p-1444444200919.htm

I haven't done my solar study yet so I may be asking dumb questions but here goes...

Would this work on the house batteries? We have a 12 volt cigarette-type outlet in the cabinet over the passenger seat that links to the house batteries.

How long is the outlet-to-solar-panel cord and is it proprietary? I have no doubt a much longer cord would be needed to reach up into that cabinet.

Did you figure out why you were getting a dead battery in the first place? Our Phoenix has gone months without being started and cranks right up. That said, we did manage to kill the battery once but I seem to recall it was before we learned to lock out our steps. They get bored and like to play when no one is around. We plan to get them fixed someday.

I am guesstimating the cord is only about 5 ft and you will need to splice in more wire . Scroll through the pictures to see the 3 types of connectors that are included.

The 12v socket   above the passenger seat won’t have continuity to the house batteries when the coach battery disconnect switch is in the off position, and turning it on would defeat the purpose . But you could connect the solar panel battery clamps directly to the house  battery terminals for the inverter, using this wiring diagram as a guide.
http://keelhauler.org/RV/2552Electricalwith_SolarArrays&Monitor.jpg

The 12v socket   above the passenger seat won’t have continuity to the house batteries when the coach battery disconnect switch is in the off position, and turning it on would defeat the purpose .
http://keelhauler.org/RV/2552Electricalwith_SolarArrays&Monitor.jpg

I was thinking of a trickle charge to help support the fridge when boondocking. Don't really know what the electric usage is in that case. We're currently struggling to keep our fridge from faulting on DC. Our Norcold has a cool diagnostic feature and it says it is having trouble with the igniter so we're buying it a new one for peace of mind. We can't get into a local repair shop until mid-July or later so We are stuck with our lame fix-it skills. We hope the new igniter solves our issue but thinking it through made us realize our PC will spend four days/three nights in a ferry parking lot and we can't keep an eye on the fridge as we will be on Isle Royale. I'm not comfortable rigging electrical cables so it is a moot point if I don't have a cable long enough to connect the solar panel. I wouldn't leave solar stuff outside the RV for that time either so the clamps won't work this time. Thanks for the cool toy idea though.

We do almost exclusively boondocking, so having a charged RV Battery is something of a requirement.   What has worked for us has been the utilization of  "50W Complete Kit Folding Portable Solar Panel Off Grid 12V Camping Home Caravan".  (That's what they call it).  It folds, which helps with the limited storage space in our 2100.   Since the unit can be positioned, it can be located where it will receive the best light.  The 3 amp output is not going to keep up with a heavily used battery, however, we found it enough to allow seven days of regular use (our current maximum days off-grid).  Nice to not have to start up the generator in order to charge the battery.  Of course, YMMV.