Is Ground Loop Hum possible with multiple battery powered devices connected together?

[Hasbro]

Baseline)
I've got a a new Orangewood Juniper guitar (passive pickup) that I connect directly to the Bose s1 Pro, with zero resulting hum. In all cases, I am running the Bose on battery power, disconnected from wall outlet).

Scenario 1)
I put a small pedal board powered by battery between Orangewood guitar and Bose, I get a ground loop hum (as evidenced by its silencing if I touch anything metal on the pedal board such as a footswitch). The battery powering the pedal board is a Milwaukee Top Off (a standard outlet you stack onto a 12 amp tool Lithium Ion battery)


Scenario 2)
If I plug that pedal board into the standard wall outlet (instead of wall outlet), no hum with the passive Juniper.


Scenario 3)
This is really strange, but if I use my Gibson with an active Baggs VTC in scenario one using battery power for the pedal board, the hum disappears.


I've ordered a Morley Hum X to see what happens.

Anybody know what is going on here? My goal is to be able to use either guitar with the bose/pedal board in full on battery, I got the gibson working but the passive pickup for some reason is a different back of tricks....

[RogerPease]

I suspect the Milwaukee thing is noisy. Tools don’t care about noise.
Tying the grounds together might help. _RP

[Hasbro]

Originally Posted by RogerPease

I suspect the Milwaukee thing is noisy. Tools don’t care about noise.
Tying the grounds together might help. _RP

That was my initial thought, but there isn't noise on the Gibson/active pickup. just the juniper/passive pickup.