Anyone here use a separate battery to power just their Helix 9 SI? Do you put the battery under the console where you have it mounted, or in the battery box with the other batteries? What is a good battery to power just the Helix? Should I go gel or lead acid or something else? How long do the batteries last? I don't want to hook it up to the cranking battery to keep it charged when the main motor runs because there's too much interference, and when I crank it up it shuts off the Helix.
Thanks

More than likely it shuts off because your cranking battery is dropping in voltage. If you don't want to worry about acid spillage get an AGM battery. Most any size should power your Helix.

More then just powering your electronics what engine do you have and what battery do you currently have. How old is the batter. What is the CCA? You may not have enough battery causing a voltage drop shutting down Helix upon start.

I have a 1995 Johnson 130 Hp, When I got my boat the batteries were less than a year old and are, I think, 720-800 CA...When I first installed the unit it worked fine, but after a bit of fishing, using the trolling motor (maybe 30 minutes) I went to crank up the motor and it shut off and rebooted. Every time I would crank it up that would happen. I moved it to the secondary battery and it seemed better. I have a 12V trolling motor that is a MinnKota Terrova, iPilot. It draws a lot of current so I split the load using 2+ wires, and 2- Wires. One set from each battery (so they're in parallel) so the load is split between the two batteries. There was one set of trolling motor wires there and it was only 10 gauge and the original plug melted with the Terrova running on that one set of #10AWG wires, which is why I added the second set to split the load. I have the Helix connected to the battery that goes to that, AND the other electrical accessories (bilge pump, dash, radio etc). I just thought maybe a battery on its own for the Helix would be better for it so it wouldn't get any counter EMF from the other motor(s) running, or feedback/power surge from the alternator on the motor to keep the cranking battery charged...One battery is cranking only, so I don't drain it to the point the motor won't crank up.
EDIT: I guess it's not cranking only as the trolling motor runs off of it (well, half the current anyway...)

The trolling motor should not be connected to the cranking battery. You would be better off using 2 batteries for the trolling motor and one for the engine than the way you have it. I'm surprised you can start your engine late in the day.