Battery Charging and Isolation

I felt that way too.... needing to use tow/haul or lights. Just came back from a trip and kept that in mind. It was useful to use the tow/haul with the TC in the bed... esp. with the boat behind. Also figured that burning the lights wasn't a bad thing either (makes the 3500 look cool too). Easy Peasy........

BTW - From the 2015 3500HD Owners Manual - section 9-93:

Heavy-Duty Trailer Wiring Harness
Package
For vehicles equipped with
heavy-duty trailering, the harness
connector is mounted in the bumper.
The seven-wire harness contains
the following trailer circuits:
. Green/Violet: Left Stop/Turn
Signal
. Yellow/Gray: Right Stop/Turn
Signal
. Gray/Brown: Taillamps/Parking
Lamps
. White: Ground
. White/Green: Back-up Lamps
. Red/Green: Battery Feed
. Dark Blue: Trailer Brake
If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode
button, if equipped, at the end of the
shift lever. This will boost the
vehicle system voltage and properly
charge the battery. If the trailer is
too light for Tow/Haul Mode, or the
vehicle is not equipped with Tow/
Haul, turn on the headlamps as a
second way to boost the vehicle
system and charge the battery.
Camper/Fifth-Wheel Trailer Wiring
Package
The seven-wire camper harness is
under the rear bumper, attached to
the frame near the rear
crossmember. A connector must be
added to the wiring harness that
connects to the camper.
Chevrolet 2015i Silverado Owner Manual (GMNA-Localizing-U.S./Canada/ Black plate (94,1) Mexico-8425172) - 2015 - CRC - 6/20/14
9-94 Driving and Operating
The harness contains the following
camper/trailer circuits:
. Green/Violet: Left Stop/Turn
Signal
. Yellow/Gray: Right Stop/Turn
Signal
. Gray/Brown: Taillamps/Parking
Lamps
. White: Ground
. White/Green: Back-up Lamps
. Red/Green: Battery Feed
. Dark Blue: Trailer Brake
If the vehicle is equipped with the
heavy-duty trailering option, see
“Heavy-Duty Trailer Wiring Harness
Package” earlier in this section.
When the camper-wiring harness is
ordered without the heavy-duty
trailering package, a seven-wire
harness with a seven-pin connector
is at the rear of the vehicle and is
tied to the vehicle's frame.
Electric Brake Control Wiring
Provisions
These wiring provisions are
included with the vehicle as part of
the trailer wiring package. These
provisions are for an electric brake
controller.
The harness should be installed by
your dealer or a qualified service
center.