I have a 2021 190 TXW. It is equipped with two 27M deep cycle batteries for the Ultrex 24v trolling motor. I also have a 27M starting battery for the engine and electronics including a Helix 10 fishfinder and a Mega 360. I upgraded this battery from a 24M when i added the Mega 360 and changed out the fish finder from a 5" Lowrance to the Helix 10. I will be adding another Helix 9 fishfinder this winter. Do I now need to add a dedicated battery for the two fish finders and Mega 360 or can I just power it from the exsiting starter battery?