Alternator charging with Victron DC-DC -- isolated or non?

[DerekW]

Hi all. New to this.

Recently had my Toyota Tundra truck setup with power running off the alternator. I plan to use the power to charge the battery bank in my truck camper.

Installer added a switch and ground the negative.

I have red & black (+/-) cables to work with now in my truck camper that sits in the bed of the truck.

I wanted to use the Victron DC-DC 50A charger. As I understand it, I should choose the non-isolated version given that my negative is grounded.

That said... why do I have the black cable running to the back? Should I just leave it capped and ignore it? Bit confused by its presence if I'm grounded.

Link to Victron unit I'm considering:

Amazon.com

 

[Rocketman]

You say your vehicle is a “truck”. We need a little more detail to verify first.

Is it like a truck with a tow behind RV, so the alternator is in the truck - but the battery being charged is in the trailer? Because this has two completely independent batteries with a marginal electric connection- this style needs an isolated Dc-Dc charger.

Or is you charging battery attached to the truck - like in a MotorHome. Both batteries are tied very well to the same frame - this style uses a non-isolated Dc-Dc charger- the Amazon linked one will work perfectly in this case.

Tell us a little more please.

 

[DerekW]

You say your vehicle is a “truck”. We need a little more detail to verify first.

Is it like a truck with a tow behind RV, so the alternator is in the truck - but the battery being charged is in the trailer? Because this has two completely independent batteries with a marginal electric connection- this style needs an isolated Dc-Dc charger.

Or is you charging battery attached to the truck - like in a MotorHome. Both batteries are tied very well to the same frame - this style uses a non-isolated Dc-Dc charger- the Amazon linked one will work perfectly in this case.

Tell us a little more please.

Ah. It's a Toyota Tundra truck. Typical alternator and battery setup in the truck itself. The camper sitting on the truck will have it's own battery bank that the alternator power will be charging. Thanks.

 

[Rocketman]

Ok being a camper… I don’t know which one you should use.

You may want to message your Victron dealer and ask them.
The Amazon link says Bay Marina Supply.

My guess is if you have a 6awg negative wire that attaches the two frames (camper and truck) together you could use the one you linked. The one you linked is a great unit.

The Dc-dc charger needs a negative wire that connects to both the alternator negative (truck frame) and the camper negative. It needs 50amps of connection.

Good Luck!

 

[DerekW]

Ok being a camper… I don’t know which one you should use.

You may want to message your Victron dealer and ask them.
The Amazon link says Bay Marina Supply.

My guess is if you have a 6awg negative wire that attaches the two frames (camper and truck) together you could use the one you linked. The one you linked is a great unit.

The Dc-dc charger needs a negative wire that connects to both the alternator negative (truck frame) and the camper negative. It needs 50amps of connection.

Good Luck!

Thanks. Probably should reach out. They do have the non-isolated version, which I could just plug both into... I was just trying to figure out if that was really needed.

 

[DerekW]

Thinking I may need isolated because I won't have a common ground between the two batteries. The fiber glass camper battery wont be grounded to the vehicle

 

[DerekW]

so the answer is to take the negative from the starter and place it on the negative bus bar along with the ground out of the unit to the bus bar