Positive Negative Chasis

[EdRedBird]

Following this thread still looking for a clarification
My starter battery Black (-) is wired to the chasis.. ..and my (-) on the dc controller
My house batteries are also connected to DC(-)
So my house battery...is connected to the chasis

WHY..... should I (or is it best practice <or not>) to wire any device back to source ...rather than connect their negatives to chasis?

 

[ctc]

Wiring to chassis uses less wire but can be a nuisance.

 

[scotjimland]

it's also best practice.. connections to chassis have a habit of getting corroded.. I recently had a fault on a 7 pin trailer socket.. traced to a poor earth connection behind a tail light on the van

 

[bigtwin]

The main issue is that, if you have a Battery Monitor/Shunt, then wiring direct to the chassis bypasses this. Consequently, your battery monitor cannot provide a true indication of the battery state.

Ian

 

[St3v3]

The main issue is that, if you have a Battery Monitor/Shunt, then wiring direct to the chassis bypasses this. Consequently, your battery monitor cannot provide a true indication of the battery state.

Ian

If the instructions have been followed correctly this is not true.

The ONLY connection to the -ve of the battery bank should be the shunt. A link to chassis is from the other side of the shunt.

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[bigtwin]

If the instructions have been followed correctly this is not true.

The ONLY connection to the -ve of the battery bank should be the shunt. A link to chassis is from the other side of the shunt.

Good point, well made.

Ian

 

[autorouter]

Motor vehicles are usually made of substantial metal, and the idea of the chassis connection is to save the weight and expense of the negative return wire to the battery. The return current flows back from the device to the chassis, along the chassis, and from the chassis to the battery. This system works fine for almost all vehicles on the road today.

Coachbuilt and A Class motorhomes are not usually made of metal, but are made of foam sandwiched between metal, fibreglass or plywood. There is no obvious path for a return current, so much motorhome wiring has both positive and negative wires back to the distribution/fusebox.

However the alternator negative is always connected to the chassis, as is the starter battery negative. So to charge the leisure battery from the alternator, the leisure battery negative is connected to the chassis too. And for other wiring it makes sense to use the chassis return if it's convenient.

 

[RogerIvy]

Also, as the chassis is like a massive cable with no voltage loss may as well make use of it.

 

[mitzimad]

no reason you cant use the chassis as earth when i did a self build i put one earth point each side of the van to make fault finding easier

 

[donkey]

Good advice above. By fitting dedicated earth points at suitable positions on Chassis, you can ensure good connections, check periodically easily and it makes fault finding easier.

Geoff

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