DC-DC Charging ?

BFL13 wrote:

As is, the truck and camper batts are in parallel with the 7-pin connected whether or not the ignition is on. I left the 7-pin connected for the signal lights etc, but disconnected the charge line so now no "alternator charging".

My Dad many yrs ago when trucks came factory with no trailer hitch or wiring connected the charge line constant battery hot..

Worked OK, but discovered by accident that it was actually a bad idea when he was caught traveling in a severe snow storm and had to get off of a now closed Interstate at the nearest exit.. And found a closed gas station to pull into.

Had to run the furnace in his 5vr all night, the next morning he discovered that the furnace not only flattened his RV battery but his trucks battery.. Now he was stuck in a snow storm with no way to start his truck, no heat, no solar panels, no gen.. Had to wait for someone to open the gas station to get a jump..

Discovered the hard way that needed to test the trailer battery and replace it when weak periodically, and never leave the trailer plugged into the truck overnight..

Because I KNOW this can happen (even to the smartest folks) trying to remember everything that must be done manually can and will eventually bite you in the behind..

I try to automate things as best as possible so I have far less things to deal with or remember to do.

If trickling your vehicle battery is an issue when parked and you have shore power, I would suggest a cleaner way to do this is to buy a small ready made multistage chargers that is designed for that job and run it from 120V..

I bought one of these..



To use on my whole home generator, 12V three stage at 5A..

Bought it back in 2018 and so far, I have zero complaints, it seems to keep the starting battery in tip top shape.. Automatic charging, no buttons to remember to push, no need to disconnect it.. Just lights up and charges and does it's thing when 120V AC is present.

$36 HERE

I am sure you could easily setup a 120V connection back to your truck to make that happen..

Adding that would allow you to isolate charge line with a relay that is turned on via ignition key.

All fully automatic, no more voltage differences worries..

Generally though, you should be able to park your truck for several months without the need to charge the truck battery.. If you have to have a constant charger on it, you may have issues with something drawing power (IE something not turning off?).

Good FLA batteries can easily sit for two or three months or so without the "need" of being recharged provided there is no other major current drains than the battery self discharge and if connected to the vehicle only radio memory and body control computer drain..