Victron DC DC charger (isolated or non)?

[DuncT]

Quick one.
I'm moving across to lithium and need to change my DC DC charger.
I'm planning to get the Victron 50a one and turn it down to 30a so I can use my existing wiring but should I get the isolated or non-isolated?
I think it's the isolated I want?

I'm going to follow these instructions as I also have a EBL control system...

Retrofitting a DC-DC charger to a Schaudt/Lippert Elektroblock (EBL) system

This document serves as a comprehensive guide for those looking to upgrade their existing motorhome systems by fitting a Roamer LiFePO4 lithium batter...

support.roamer.com

Cheers all for help/advice.

 

[Lenny HB]

You need non isolated isolated ones are for boats.
It's best to wire it direct between battery and bypass EBL & switch it via the D+.

 

[autorouter]

Non-isolated, as Lenny HB says. In a vehicle, the starter battery negative is connected to the chassis, which connects to the alternator negative via the metal of the engine block. In order to use charging from the alternator, the leisure battery must also be connected to the chassis or to the starter battery negative. So the negatives are always connected together, so the batteries are not isolated at all.

Since a non-isolated DC-DC charger is less expensive than an isolated one, it makes sense to use that type. However if you already have an isolated DC-DC charger, you can join the two isolated negatives together and use it like a non-isolated one if you want.

I'm going to follow these instructions as I also have a EBL control system...

The final paragraph of the instructions refers to wiring a DC-DC charger over 30A. It says you should wire a high-current relay to disconnect the EBL starter input from the starter battery when the engine is running, and reconnect it back again when the engine is stopped. For almost all EBLs, that is unnecessary. The starter battery input at the back of the EBL only connects to the split charge relay inside the EBL, and it does nothing else. All the other functions that use the starter battery have a second supply wire that goes into the front of the EBL.

The high current relay disconnects the wire when the engine is running, as required. However when the engine stops, there is noneed to reconnect the wire back again, because it doesn't do anything. Instead of a relay, it is sufficient to simply remove the fuse in the wire to the back of the EBL. The fuse is located near the starter battery. Or you could disconnect the wire from the back of the EBL, and tape it up so it doesn't cause any problems.

Using a relay like this is necessary for other distribution/fusebox brands found in other motorhomes, such as CBE, Sargent etc. For all but the oldest EBL boxes, it is unnecessary.