Battery charging from Tow Vehicle

[geoffrey chew]

In an attempt to reduce voltage losses whilst charging from the Tow vehicle I have run 2 x 10 AWG leads from the rear compartment RV batteries in my 2720SL and connected them into the 10 AWG pos and neg wires in the trailer cord in the area of the fridge. So there are now two DC charge circuits leading to the batteries. With RV batteries fully discharged (12.0v) the charge current from the TV alternator increased from a previous 5A to 17A, that is to say the new lower resistance circuit contributed 12A. I then ran the converter and measured 35A flowing to the RV batteries, of which 30A was delivered through the old charge lead with an additional 5A flowing through the new lead. On the face of it this seems to offer a big improvement for TV charging with no foreseen downside when charging from the converter. However I would appreciate comment from our electrical techies.

[Bill]

Geoffrey -

Congratulations! That was my experience as well, as discussed in post #22 here.

Only one caution. The new wires must be fuse-protected, just as the orignal ones are. And that means a fuse (or circuit breaker) at both ends of the new hot wire.

Bill

When in tow/haul mode my alternator uses a higher output voltage, to compensate for the increased distance to the trail batteries.

My owners manual does not say if that higher voltage is everywhere or just for the power wire back to the trailer.

If, somehow, the voltage to the rest of the TV remains at the lower voltage then I think it would be important to make sure that both wires are using the same voltage.

If the higher voltage is used for my entire truck then this does not matter.

If you attach both wires under the hood to the same post then it does not matter.