House battery ground/return path

[Dazed]

I am designing my house battery system at the moment and had a question about grounds/return paths. On the house side, if I have a load, lets say a cigarette lighter, can I tie that return to chassis anywhere, or do I need to make an effort to tie to back as close to the house battery as possible?

Basically I am asking, is it ok that the starter/vehicle battery and the house battery share the same return path (the chassis/body/etc, which I see as a ground). Do I need to worry about their return currents since they will be on different sides and a DC-DC converter?

As a note, in high-end electronics systems, using the ground plane/chassis as a return is a no-no. Also, note a when I say ground, I do not mean a true ground, which is a big metal pole many feet into the ground, but the voltage reference plane.

 

[ntsqd]

I would imagine that a DC-DC converter has a ground wire on the output side? If so then I'd make that common to everything running off of the converter and isolated from the chassis. If it doesn't, then I'd question if that's really the converter that I want to use.

With high current loads and sensitive electronics I run a dedicated wires/cables sized for the total circuit length (including the ground run) at an appropriate voltage drop. Non-sensitive electronics & electrical get a chassis ground.

 

[Dazed]

Sounds reasonable. What do you consider sensitive?

To me sensitive is my electronics test equipment at work like o-scopes.

 

[ntsqd]

Sensitive: EFI (sometimes - wire it how the OE did it), ham radios, car-puters

Not sensitive: car stereos, cb's, HID ballasts (< can make a quiet system noisy when cheap)

car stereo amps straddle the line, good ones aren't, not so good ones are. With a noisy system can probably make a good one not so good.

 

[rusty_tlc]

Noise aside you can also see less than 0 Vdc in your ground if the return path has high resistance (ie the chassis) this has the result of reducing the apparent applied voltage at the device. If your using a chassis ground wire brush the paint and undercoat away from the area where you attach the wire. Be sure to reseal with paint or undercoat after to make your connection to prevent corrosion in the terminal.