I’ve used my 12v TM and graphs and drained them down enough on long days that the graphs started blinking when I got on the TM. I do tend to just put it on high and troll around instead of using the motor though.

If you are vigilant about keeping your cranking battery fully charged and well maintained, no problem running them off the starting battery

There are few things worse than getting to the lake with a discharged cranking battery (especially if you’ve just driven 2hrs to get there)—-yes I jumped off my fishfinder battery

I thought I was charging the cranking battery with the onboard charger at storage location, but I wasn’t. Had to fix some wiring.