I'm installing a Bluerail 5Amp board and connecting to a Tsunami decoder. Because of reasons, the BR board is in the tender, the decoder is in the loco boiler.
I have a10 pin connector that I am using to join the tender and the loco. I also have in the tender the 12V battery, the Speaker, a backup light and a coupler coil.
I'd like to run a DPDT selector in the loco to allow me to switch between track power and DC power. It also acts as a convenient "off" switch to switch of the DC when not in use (just switch to track power whenever I don't want to run) to prevent the battery from draining.
With my rail pickups and the DPDT switch in the loco, I'm one pin short on my connector to control everything in the tender. I'd like to not sacrifice any of the features, so I'm wondering if I can run the negative output of the battery directly to the Bluerail board and only switch the positive. Is there an adverse effect on the BR or DCC circuits if they are still connected to the negative battery terminal when I'm running off track power? I would think that with the positive switched off and the loop to the battery open, it shouldn't, but I've read enough about DCC acting strange to figure I'd run it by you guys.
See image below. The blue +10.5V is coming off the Tsunami decoder to run the backup light and the coupler. Bluerail says polarity on the PWR and DCC terminals is not important, so I didn't mark them. They also say the 5AMP board can take AC directly (the smaller boards need a bridge, but the big board is OK right off track power from my understanding). You can see the empty pin on the ground side of the DPDT switch.