Run PV- wire direct to chassis?

[gongloo]

Apologies for the possibly dumb question here, just getting started and have a lot to learn!

I’m working on a van conversion and went with Renogy’s DCC50S, on which there’s a single terminal for shared solar negative, house battery negative, and starter battery/chassis negative. What I’m wondering is, since all of these are going to be connected to chassis anyway, is there really a need to run a separate negative wire from the solar panels on the roof all the way down and around to the charge controller directly? Wouldn’t it be equivalent to instead run a negative wire from the solar panels to a solid ground point somewhere closeby, and then use the chassis to carry the current the rest of the way to the charge controller?

Coming from the automotive world, I’m not used to ever running a negative wire back to the battery, and instead pretty much just run it back to any chassis ground point I can find nearby. Having read a bit now about ground loops, I understand how this can be a problem with ground wires of different lengths, especially with AC, but in a DC system grounded via big honkin’ metal chassis (presumably with negligable resistance), I expect ground loops shouldn’t be much of a problem here?

I’m no electrical engineer, so I’d appreciate the input of more learned people. Thanks!

 

[snoobler]

There are no dumb questions. There are only inquisitive idiots.

This is not in evidence by this inquiry.



Given the label for #4, I would assume it's acceptable to send the panel (-) to the closest ground capable of handling the panel current provided there is a suitable breaker/fuse on PV+ between panel and charger.

 

[Zil]

As there are many ways for chassis grounds to fail or develop higher resistance. I use a return wire for critical circuits and for heavy currents. My inverter is an example of heavy current. My charging circuits are example of critical circuits. While they do tie onto the chassis as a common ground, I also use a return cable to the negative buss bar. In regards to the panels, to the charge controller. I am the enemy of voltage drop. There is no need for a fuse or breaker on the panel to CC. There is a need for a disconnect switch.

 

[HRTKD]

In my RV trailer I did NOT use the chassis. Perhaps it is better to say I did not rely on the chassis. All my components tie into a negative bus bar. Charge controller, inverter, converter and batteries all go directly to the negative bus bar.

There may be portions of the system downstream from the upgrade I made that does tie into the chassis.

Renogy may be expecting you to have a common bus bar, not necessarily the chassis.

 

[PictureMeFree]

In my RV trailer I did NOT use the chassis. Perhaps it is better to say I did not rely on the chassis. All my components tie into a negative bus bar. Charge controller, inverter, converter and batteries all go directly to the negative bus bar.

There may be portions of the system downstream from the upgrade I made that does tie into the chassis.

Renogy may be expecting you to have a common bus bar, not necessarily the chassis.

Is your negative buss bar connected to chassis?

 

[toms]

There is no problem using the RV chassis for the negative path provided the chassis to wiring connections are well designed.

It is likely to be easier, cheaper, and neater to run a twin wire from the panel to the SCC though.

 

[HRTKD]

Is your negative buss bar connected to chassis?

Not directly. The common bus bars used by the new components (batteries, shunt, fuses, converter, inverter, solar charge controllers) have leads going to the trailer's existing main distribution panel. That panel has a negative bus bar that has a wire going to the chassis.