24v to 12v on a boat

[Skunksmash]

Hi all. I'm trying to rig up some LED docking lights, and side lights on my pontoon boat. I have the engine battery, and a 24v system for my trolling motor. The 24v is just 2 12v batteries.

My problem is, I really don't want to run lights off of the engine battery. They may be LEDs, but after everything is installed, there is a potential power draw of about 200 watts. Doesn't seem like a good idea to draw that kind of power off of your ignition battery. Wouldn't want to get stranded out there in the middle of the lake somewhere.

So what is the best method, of stepping down my 24v system, without creating an imbalance? I had heard that there is a method, that doesn't use a resistor setup of any kind. I'd like that, because resistors of course create heat which is wasted energy. But if that's my only choice, that's what I'll do. Any ideas?

[71swb4x4]

I would use the 12 volt battery and install a low voltage shut off switch, so it shuts down when the voltage drops to a certain level. Then you know you need to start the engine and get some charge going again.

[Skunksmash]

What about running both 12v batteries in the 24v system, in parallel instead?

Leave them in series, but just run a wire from both positives, and both negatives, to a fuse box, and then of course to the lights. Would that work? To me that seems like it should come out at 12v. Any disadvantages to doing that?