[Gemaskerde Tuinvurk]

Is there any specific reason this should not be done?

Measured my cable out at the rear of the car: pos to neg, gives about the same voltage as pos to chassis.

In theory could you not just fit a thick pos cable to the back and then ground to chassis?

[4ePikanini]

yes it should be fine but most run both cables to the back paired with a dual battery system - that way you can have the secondary battery completely separate from the main battery for fridges etc. - so it doesn't interfere or drain your main battery.

[LowRange]

Is there any specific reason this should not be done?

Measured my cable out at the rear of the car: pos to neg, gives about the same voltage as pos to chassis.

In theory could you not just fit a thick pos cable to the back and then ground to chassis?

Remember that you are measuring the open circuit voltage!

The moment that you start pulling major amps to recharge a battery, the resistance of the return path to the alternator negative via the chassis and various other bits and pieces will result in a voltage drop - which is what you are trying to avoid in the first place.

Pull proper cables for both positive and negative.

Johan