24v down to 12v?

[Gasser64]

I'm trying to rig up some LED docking lights, side lights, and a few others on my pontoon boat. I have the 12v engine battery, and a 24v system (2x 12v batteries) for my trolling motor.

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.

[lowthreeohz]

Why not just a cheap 24-12 step down? You can probably pick one up for $20

[91CoupeMike]

Why not just a cheap 24-12 step down? You can probably pick one up for $20

Because Justin.

He once rambled of using a small mower engine to turn his accessories to get better mpg.

[Tremor14]

so the OP is into Docking??

[Gasser64]

Why not just a cheap 24-12 step down? You can probably pick one up for $20

Yeah that's the first thing I was going to do, this:

http://www.amazon.com/HOSSEN%C2%AE-Converter-Regulator-Step-Down/dp/B00BWKXTUU/ref=sr_1_1?s=electronics&ie=UTF8&qid=1439496271&sr=1-1&keywords=24v+to+12v

Resistors are in there though, so I was going to try to avoid those. But again if that's the best way that's what I'll do. Just thought I'd ask in case there were any electric gurus in here.

[R3_82GT]

Resistors?

Anything you use to step down voltage is going to generate heat - its physics. Just resistors is about the most inefficient as the excess voltage is just watts (heat)

I can't say if the amazon box is good or not , but it is more than just resistors. Resistors don't need reverse polarity protection or short protection .
Really you want something solid state (transistors , voltage regulators etc) to be most efficient (if you care about efficiency).

The other choice is a step down transformer - but just buying one of those is not going to be packaged - and I would still want some voltage regulation on the 12 volt output side.

[svauto-erotic855]

Most LEDs run/burn the same at 24v as they do with 12v. Just hook one up to 24v and leave it going for a few days to see what is does. If it doesn't flame out after a few days you are good to go. There are also plenty on 24v speced lights out there. You could also just carry a jumper box with you.

[R3_82GT]

Are you sure abut the 200 watts (especially for LEDs) ?
I always design LEDs using 20 milliamps
200 W /12 volts = 16.67 amps
16.67 amps / .20 amps per LED would be over 800 LEDs.

[Gasser64]

Most LEDs run/burn the same at 24v as they do with 12v. Just hook one up to 24v and leave it going for a few days to see what is does. If it doesn't flame out after a few days you are good to go. There are also plenty on 24v speced lights out there. You could also just carry a jumper box with you.

I'll give that a try, since I have some LEDs to spare. Also I'm not really wanting to carry a jumper box since its on a boat and space is a concern. And admittedly, I'm an electricity noob. I only know the basics at most. I had always heard that devices will only draw what power they need.

Are you sure abut the 200 watts (especially for LEDs) ?
I always design LEDs using 20 milliamps
200 W /12 volts = 16.67 amps
16.67 amps / .20 amps per LED would be over 800 LEDs.

You can buy just 2 LEDs, both 100 watts a piece of you want. The wafer is roughly the size of a silver dollar. They're quite large, as LEDs go. They have to have their own cooling. This guy used one in his flashlight. That said, that may be too much, I may end up going with 50 watts or 25 watts for the docking lights, not real sure yet. I was just throwing that out there as a max power draw so I could plan accordingly.