I just hooked up a MegaLive to a Helix 12. I also have a dual spectrum transducer and Mega 360. And I have a new cranking battery. My MegaLive worked initially and then quit. I got a MegaLive "source lost error message". The Humminbird tech says it is low voltage and it does drop to 11.9 volts which Humminbird says is too low.
Anyway my buddy says there is a sort of rechargeable pack fishermen are using now. It'd be similar to a recharge drill type system where you put a charged lithium battery pack in and use it until it gets too low and then you'd drop another pack in. Anybody have an idea as to what system this is or where one would buy it? I spent pretty big dollars on my cranking battery. It could be bad but if not, I don't have room for another 12 large battery and I'd like to use MegaLive.

How is you system powered, direct runs, fuse panel from the the boat, separate fuse panel, size wire used to power the system?

I have a Skeeter ZX 250. I originally had a Lowrance Gen 3 on the bow. In the original setup there was the Lowrance power wires and then another set of power wires in the bow. I used the extra set. They likely run through the fuse box at the console. I have the wires available that powered the Lowrance. All wires show 12.5 volts at the bow. But the volt meter on the Humminbird shows perhaps 11.9 or 11.8 volts. I'm going to power the MegaLive with the old set of power wires. But all wires lead back to the cranking battery which is a brand new Group 31 battery. The only possible problem that I see is if the cranking battery is not good. My three group 31 Interstate trolling motor batteries charge up quickly but the cranking battery takes longer. It charges but not as quickly.

With that set up you need a big AGM 31 group battery. Humminbirds are notorious for pulling a significant amount of power. We have the Pro Guide 31AGM in stock. Luckily it will work with any Minn Kota charger that says PC on it. Such as the MK 230PC, MK330PC or MK 440PC.

I have (4) Group 31 batteries. My buddy was informed that many Humminbird users have to hook up another battery to power all the HBird options. I ordered a 30 amp hour 12.8 volt lithium battery and charger. I'm going to put the battery in my starboard rod box. I'm going to run the MegaLive off this battery.

What gauge is the wire from the battery

First look at your battery. I just upgraded to a group 31 AGM from X2
Also upgraded my stock,FX21 wire., to a Sea Clear harness with heavier gauge wire and a Perko shut off switch.

You were doing ok with your starter battery before adding MegaLive weren't you?

Thanks all for the recommendations. Based on some info from a buddy, I decided to go with a 12.8 volt Amped 30 ah lithium battery with 12 gauge wiring. I'm going to install a Perko switch and place it in the right rod storage box and strap it in. This will be about 200 bucks with the charger. The MegaLive works pretty well. I have a lot of stuff on my trolling motor now.

Yes, Mega360 and DI worked great. MegaLive messed it up. And it seems Humminbird was well aware of the problem. Everybody needs a 30 AH 12.8 volt lithium electronics battery. They aren't that expensive and considerably less than each of the Interstate Group 31 AGM trolling motor batteries I bought last fall.