Battery Charging Systems

Hi Fj Ute.

The way I understand what you have written is that the dry cell battery for the camper is a cranking battery.?? is this so?

I would assume that the better battery for a camper would be a deep cycle in agm configuration of at least 100 amp hrs rating.

Voltage drop is the issue for charging a battery back in the camper.
So run good sized wire, and good connectors at the tow ball, 50amp anderson plugs seem to be the weapon of choice.

Short answer is that you can charge all batteries together when driving.
Alternators can put out 80+ amps, so can easily take care of the initial bulk stage of charging, its crude, but will work to a point.

This, if given enough travel time, and depending on how many amp hrs have been used in the battery should get you back up to near 80 % or more state of charge.
The last 15% or so takes a bit longer.
This is where a dc dc charger can help, or a solar panel/ reg setup.
Or just plug into 240 if at a caravan park, and use a good quality step charger to top up the batteries overnight.

Hope this helps a bit, but I think we need some clarification on what type of battery they are running in the car as a 2nd battery, and also the type in the camper trailer.

cheers

Trains

Do not try to charge 3 batteries from one alternater. Each battery will take 25 amps so if you have a 80 amp alt. You will burn it out as it will get too hot