DC to DC charging from Dual alternator/ battery setup

[Ghost79]

I have a 2021 Dodge Ram 3500. It has dual alternator/ batteries. I'm going to be installing a Renorgy 50 A DC to DC charger. I plan to pull power from the passenger side battery but would like some feedback on this.

I read that all of the charging feeds to the passenger side battery first then the actual voltage monitoring is performed on the driver's side. This can result in consistently overcharging the passenger battery. I just had to replace this battery. So if I'm going to pull extra load out it seems reasonable to pull it out of the passenger battery to increase it's longevity?

Anybody have experience with this?

 

[Skinhyfish]

Choose your accessory battery over your start

 

[StenchRV]

RAM does have the alternators wired so they can not be separated, aka one for the engine and one for the habitat unless you do some computer work. It gets messy according to the techs I talked with.
They work together. Dual 220 amp alternators on my rig. Dual Victron DC-DC 50 AMP wired one passenger one driver.

Actual testing with a high end clamp on Fluke amp meter. Tested 8 inches from EACH alternator output.

DC-DC OFF Drivers ALT output 17.5 AMPS Passengers 22.3 AMPS
DC-DC ON (both) Drivers ALT output 70 AMPS Passengers 73 AMPS

1200 RPM with the AC running on medium.

Hope this helps a little. If I was home I could shut down the drivers side and let you know. Traveling Newfoundland now.

CHEERS!!

 

[Peter_n_Margaret]

I don't understand how an alternator can overcharge a battery unless the output voltage of the alternator is too high.
Cheers,
Peter
OKA196 motorhome

 

[DaveInDenver]

I don't understand how an alternator can overcharge a battery unless the output voltage of the alternator is too high.
Cheers,
Peter
OKA196 motorhome

An alternator can only be right for one voltage sense. So it would worry me that this is possible based on what @StenchRV says about the two alternators having some dependency on each other. Seems odd that Ram would do that but who knows what assumptions were made.