Just to keep relevant info in the appropriate place ...

In another thread I asked Drivesafe ...

"Using the USI-160 ... is it better to keep the aux & crank battery "shared" ALL the time, or keep the aux' "isolated" normally, only using "shared" mode when actually running accessories.

When it's being used as a daily drive, the D2 isn't running a fridge or any accessories.

The batteries are both Optima's ... D31A + D34"

Tims reply ...

"Unless the is a specific reason, the USI-160 gives the best results when operated like the SC80, in SHARED Mode ( switch set away from the LED )."