Sounds like you might want to install one of those solar panel trays that you lay inside the windshield on the truck dash. This plugs into a always hot 12VDC socket and should keep your battery topped off when you leave it sit for weeks on end... Most that ypu find on-line are 5WATT Panels or less. You really need to locate at least a 10-watt model or more to really help out...
Something like this GOOGLE SEARCH photo...
I had one for my OFF-ROAD JEEP setup and it did me well for years... I need to do the same thing for my 2010 F150 FX4 truck. They have too much electronics always on in the new trucks. There is probably three or four computers running all the time...
Roy Ken
My Posts are IMHO based on my experiences - Words in CAPS does not mean I am shouting
Roy - Carolyn
RETIRED DOAF/DON/DOD/CONTR RADIO TECH (42yrs)
K9PHT (Since 1957) 146.52M
2010 F150, 5.4,3:73 Gears,SCab
2008 Starcraft 14RT EU2000i GEN
2005 Flagstaff 8528RESS