Thread: Alternator smarts - who knows the answer to this?

Greg, is there also an isolator in the car (for the battery / fridge set up)? If so is it a redarc or Traxide? I think either would solve your problem (Tim from Traxide would confirm) but my understanding is with the latest DBS's you can achieve all of what you plan without any alternator issues. No doubt Tim or Graeme will jump on board with more details....
cheers

Hi Chris, I don't have a fixed second battery, it's a portable Engel battery box with its own battery management system, I just load it into the car when we go camping, and plug it into the 12v outlet in the cargo bay, and run the Engel off it when out of the car.
There's an isolator switch on the battery box though.

Hi Greg i certainly would be careful trying to achieve a decent charge rate to ANY battery using the 12v outlet in the rear. My understanding is that it is rated to only 20 or so amps and is designed only to run appliances like a fridge or similar. And you will require an anderson plug at the rear from an isolator with xircuit breakers to charge the 2 110ah batteries in the camper. If they have wired it up using the 20a wire in the hitch plug then you are in trouble. The volt drop will be horrendous

Jc

Originally Posted by GregMilner

Hi Chris, I don't have a fixed second battery, it's a portable Engel battery box with its own battery management system, I just load it into the car when we go camping, and plug it into the 12v outlet in the cargo bay, and run the Engel off it when out of the car.
There's an isolator switch on the battery box though.

It'll charge just fine BUT... its going to be very slow at charging especially if you have the fridge hanging off of it while its trying to charge.

some of the battery tank systems have a dedicated socket for limited charge current (cig/merit sockets) and fast charge ports (anderson or similar) that bypass the internal regulator and let the alternator deal with charging the battery.

No I don't run the Engel off the battery in the car, I plug the Engel into a 12V socket up front and charge the battery off the 12v socket in the cargo bay. I plug the trailer system into the Anderson plug under the rear bumper.

Hopefully all that stuff doesn't overload the in-car electrics.

Mine quite happily maintains a 100Ah AGM aux battery in the vehicle and another 100Ah AGM in my van via a simple voltage sensitive relay and decent cables to the van's battery via a 50A circuit breaker and Anderson connectors. These vehicles have a major distribution cable from the battery in the front to the right rear panel so it's very easy to connect power at the rear.

All alternators reduce charge as the connected batteries near full charge to prevent over-charging.

I was concerned about the comment using the internal sockets to charge a 100ah battery😮 however if the cabling in it is up to it then go for it. Anderson plugs are mandatory for trailer or caravan battery charging!! The alternator is easily capable and will sense the extra load required when needed.

Even my old 120a alt in the county charges 3 x 120ah happily ☺

The L322 has a 50 amp supply running to the back - you'll be fine. Alternators don't 'back off' when the batteries are fully charged, the batteries stop pulling current from the alternator. Whoever told you this doesn't understand alternators or batteries very well. I used to run twin 80ah batteries straight off the back power supply no dramas. Don't over complicate or overthink it.