DC-DC charging earth requirements (1 Viewer)

[Fellover]

Hi all,

I'm in the process of converting a Peugeot Boxer L2H2. I've got a DC-DC charger (this one: https://uk.renogy.com/dcc50s-12v-50a-dc-dc-on-board-battery-charger-with-mppt-renogy-one-m1/). It also does the solar panels, but I'm interested in the DC-DC bit at the moment.

The starter battery is in the cab floor and the charger will be in the garage, so a cable run of maybe 4m.

The instructions say I need to run a cable from the positive of the starter battery to the relevant terminal on the charger and a cable from the negative of the starter battery to the negative terminal on the charger. That makes sense.

My question is, can I not do the negative to negative bit and instead earth the negative terminal of the charger to the chassis? Given that the negative terminal of the starter battery is earthed to the chassis.

I'd like to do this to avoid buying a second length of quite chunky cable and avoid having to run it through the van. I also think that not having the second cable will reduce the voltage drop from the starter battery terminals to the charger.

Is there a reason this is a bad idea?

 

[Fellover]

Just found this () which I think answers my own question and says it's ok. I'd still be interested to know if anyone has a reason why they think it would be a bad idea / any disadvantages.

 

[autorouter]

I'd like to do this to avoid buying a second length of quite chunky cable and avoid having to run it through the van. I also think that not having the second cable will reduce the voltage drop from the starter battery terminals to the charger.

If the two batteries are connected to the chassis with thick enough cable then it will be fine. The chassis is used as a negative return path to save the weight and expense of a length of copper cable. The starter side will be fine, the chassis connection is built for the starter motor, which takes hundreds of amps. On the leisure battery side, the cable to the chassis may need to be upgraded if for example it was originally only used for a split charge relay.

The negative to the DC-DC Charger only takes the (small) current to run the electronics of the DC-DC Charger.