Chassis ground vs dedicated run? What tests can be done?

[jeegro]

I need power in the rear of the truck (~15ft run). An estimate for current is 25-35 amps (15A solar controller, 5A fridge, 600w inverter, accessories) and maybe a peak of 50+ (battery charger).

For the positive run, I'm using 2/0 gauge welding cable.

I had planned on running a matching negative cable to the battery... but is that really advised? What tests can I do? I want to maximize the solar controller.

I can think of:

- Ohm resistance (I'd need some really long test leads for the multimeter?)
- Voltage drop (The powerprobe "hook" looks like a great tool for this, as it can pump amps through a circuit, but I don't have the tool).

Any tips are appreciated.

 

[Hopeless Diamond]

It's less about the resistance/voltage drop across the frame, it's more about the bonding (at both the battery and "device" end). Making sure those connection points are very clean and solid, metal to metal, then making sure they stay that way, will save you headaches. Corrosion from dissimilar metals, not getting down to bare metal, connections loosening are all considerations.

 

[proper4wd]

Why are you running 2/0 cable for that small of an amperage load?

In any case, local chassis ground is fine so long as you also have a suitable ground cable from your battery to the frame.

 

[jeegro]

I have a nice trick for installing frame grounds - see attached photo. Consists of a flanged serrated bolt, thumb nut washer, and serrated flange nut. All stainless.

I wanted to get under 1% voltage drop, and futureproof it. I hate redoing work... in case I ever add a bunch of stuff

So you're saying it essentially depends, is there any way to test the quality of the chassis ground? How? Or is really just a pass/fail kind of thing?

 

[dwh]

IlI had planned on running a matching negative cable to the battery... but is that really advised?

Depends. As already mentioned, a frame ground will work fine as long as it's done right. However, having the positive and negative conductors widely separated can cause inductive noise which can annoy radios.

I want to maximize the solar controller.

15a at 12v over a 30' loop? You could maximize that with #14 wire, so anything bigger is just gravy.

Besides, part of what the solar produces is going to flow directly to the fridge and never make the trip up front to the battery anyway.

 

[jeegro]

Depends. As already mentioned, a frame ground will work fine as long as it's done right. However, having the positive and negative conductors widely separated can cause inductive noise which can annoy radios.




15a at 12v over a 30' loop? You could maximize that with #14 wire, so anything bigger is just gravy.

Besides, part of what the solar produces is going to flow directly to the fridge and never make the trip up front to the battery anyway.

Well, its not just the charge controller's 15 amps, this cable run will power a 12 circuit breaker in the rear, including lights I plan to add later. Sure, 2/0 is still overkill... oh well. I have a bunch of it. Finding where to route it is another story.

I think I will start with a frame ground and go from there.

Punching 12v, 55 variable amps, 15 feet, and 1% voltage drop into the Blue Sea calculator returns 1 AWG recommendation. I only have 2/0 and 4awg cable, so thats the thought process there

Here's the ground strip between frame and battery

 

[dwh]

Well, its not just the charge controller's 15 amps, this cable run will power a 12 circuit breaker in the rear, including lights I plan to add later.

I knew that, which is why I specifically quoted and responded directly to the comment about maximizing the solar...

I.e., you are already running a lot bigger wire than you need for the solar, so maximizing the solar is not something you need to worry about. Non-issue. Fugedaboudit.

Punching 12v, 55 variable amps, 15 feet, and 1% voltage drop into the Blue Sea calculator returns 1 AWG recommendation. I only have 2/0 and 4awg cable, so thats the thought process there

The only place voltage drop is going to matter at all is feeding the inverter - and even then it's only going to matter if you intend to operate the inverter when your battery is nearly dead.

Otherwise, "Voltage drop? Fugedaboudit."

 

[verdesard0g]

Chassis ground will absolutely work...IF.... it is done correctly. The frame of your vehicle can carry much more current with minimum voltage drop than any wire......

 

[jeegro]

Cool, thanks for the advice. I'm going to compromise and run a negative line to the SafetyHub under the passenger seat, where the inverter is also sitting, because the inverter prefers to have a direct connection from what I read. The inverter (xantrex) also has a ground wire (8 awg), and I'm not sure I can find an easy chassis ground location from under the passenger seat... what should I do with that? The negative ports on the SafetyHub share a line to both the chassis and battery, so is there any difference in simply wiring the ground the same as the negative line?

 

[proper4wd]

I have my 2000/4000W inverter grounded through a seat mounting bolt (with 2/0 cable) and it is more than enough.