Looking for guidance

[bass-n-fire]

Sorry if this is a long post, but, I need guidance.
I have. 2000 Cobra 201D. I recently purchased 2 HDS 12’s, one at the console and one at the bow. These replaced HDS 8’s. I debating on running a “house” battery for accessories and a cranking battery. I already have 4 batteries, 3 for trolling motor and a cranking battery. My trolling motor is a MinnKota Maxxum 101.
Here are my questions:
Do I really want to add a 5th battery?
How big of a battery would I need for the electronics?
Is one more battery really gonna add THAT much weight?
Benefits of 36v over 24v trolling motor?
would it be better to downsize trolling motor to a 24v and use the 3rd battery as a house battery?

Sorry for the long post. I’m already upgrading the wiring for the electronics and I do have room for a 5th battery.

[BrownTrout]

1 - Keep your 36 volt trolling motor. If you switch to 24, you'll regret it.
2 - Don't add a 5th battery just for electronics. Too much add'l weight. If you're running AGMs, as you should, they weigh ~70#.
3 - A Group 31 AGM starting battery should also handle your two graphs just fine.

I've been running two Helix 10s for years off my starting battery. I just replaced it with a ProGuide 31 AGM because it was 8 yrs old. I have both my Helix units wired directly to the starting battery.