I have been curious as to whether or not a tractor battery would run two smaller units.  I have a Helix 5 and a small B&W Lowrance. They are fairly cheap and I didn't want to be sucking down all of my cranking battery while I am graphing or fishing.  Just curious.

More than likely it would work depending on what size it is.  Is it from a regular tractor or a lawn tractor?

i am not sure on the size of cranking battery but i do know that a 12AH battery that i have for my helix 5 SI will also two full day outings pretty much.  My point is i doubt that they will pull enough to worry about the draw on your cranking battery.

I agree with flyfisher, as long as your cranking battery is in healthy condition it will be fine to run them as well.

Awesome guys.  I appreciate it.

My dad left his Lowrance Elite on one time for a whole week and it never killed the battery to the point that we couldn't start the engine