Maintaining personal car's battery while you're driving OTR

Get a battery disconnect switch

https://www.amazon.com/Ampper-Batte...,B07JYDY7FQ,B011EYWMDS&srpt=ELECTRONIC_SWITCH

 

That will foil a car thief also.

 

The thing is, when the car is turned off there is no drain on the battery unless you leave something turned on - like a light.
A shut off switch would do nothing.
That switch in the truck is so that other things, like the Qualcom or something else left plugged in, won't be draining the batteries.
It can also be used to drain the power from the Qualcom if it needs rebooting.

But in a car?
Nope. Unless you have a computer in it that stays on.

Your best bet is to get the most powerful battery that fits, and possibly have someone start the car every week or so to restore the charge.

Another option is a solar powered battery charger.
I didn't mention that first because I just had a bad experience with one.
When I got back to my car, the battery had 0.4V left.

 

I leave my car parked for up to 8 weeks at a time and have had no issues starting. I bought the car used so have no clue how old the battery is ( car is a 2017). It claims to have intelligent voltage monitoring so it will shut down ECUs etc when battery voltage gets low etc.

I bought one of those little lithium battery booster packs and keep it in the trunk Incase I ever need a jump.

 

All the modules in the car will draw a little bit of juice all the time, usually just a small fraction of an amp. Anything over 2 weeks I'd probably disconnect the battery.

 

You should make sure that the battery is fully charged. I have a battery charger that reads the percentage of charge and I have found that after a hour of driving that the battery was only 80% charged.

 

Solar trickle charger is best option, it sits on dash, I paid around $20 for the one I use on my boat.,,, battery disconnect second best IMO. Personal vehicle has block heater and trickle charger wired inline for best cold starts.

 

Get a lithium jump box on Amazon. Cheap small and very strong. Comes with cables and can charge your phone also. Left it in my vehicle for 6 months charge on the box was at 80%. Jumped my v6 that sat for a year on 1 key turn.