First time poster, beginning electrical kind of fella.

I am working on building a bowfishing boat. Lots guys run them off of generators, but I can't handle the noise, so here is what I am trying to do...

I am going to purchase 6-10 50W Led lights that are made to be used as security lights (outdoor), so they are already waterproof and all that good stuff. I want to run those lights off of a 12V Deep Cycle marine battery, most likely 2 batteries. Hoping to get 6-8 hours of life out of the batteries. I have run the numbers and should have sufficent load to power all those lights.

My hang up is what is neccessary to get from my 12v DC batteries to the 110v AC the most efficent way. Don't want to lose a lot of effective battery life through the conversion process. I want to be able to divide the lights in 2 banks so I know I will need to run at least 2 switches somewhere in there, but beyond that, I don't really even know where to start!

Any help would be super appreciated as far as where to start looking.

 

First we need to know what jurisdiction you are operating your boat.
Do you want to light up your boat like a Christmas tree while moored or do you want functional legal operating lights.
There are boating regulations that dictate where and what color of lights a boat must have while operating between the hours of sunset and sunrise.

 

I am in OK. The lighting is actual seperated from the running lights and such. I will have to have my front and rear red and whites, but they are independt from this system. Perhaps a picture will help. Didn't think about that.

Want to build a light setup something similar to this...

here is an Amazon link to the lights I am thinking about using.. http://www.amazon.com/Floodlight-Lo...1463677325&sr=8-9&keywords=50w+led+warm+light

 

The boat will be used for cruising along the bank at night. It is a seperate lighting system from the boat's main electrical system.

 

The most efficient and safest way is to use 12V marine LEDs, instead of incurring the energy losses from converting up to 120V AC and back down again to the lower voltage DC - which is done in the lamp. Though I doubt the difference will be all that much. If you go with AC then you need to buy an inverter, but at least you can use thinner gauge wire with the AC approach.

 

I also recommend using 12V LEDs.
Going to 120Vac requires an expensive inverter that will waste power. You don't want that in a battery powered system.

 

Ha! Thanks for that pic. Now it is obvious what you're trying to do.
The calculation is straight forward. Figure out the total current consumed by all the lights.
Multiply that with the number of operating hours. This will give you a figure in ampere-hours, written as Ah.
Now match that with your battery Ah rating. You don't want to use up more than 80% of your battery capacity.

 

yea, thanks for the input guys. Found a pretty good deal on some 27w LED lights. Going to take a run at using those. Next issue I'm trying to track down is this, If I am looking to run 10 27 watt leds with each pulling 2.1 amps and 3 30 watt led bars with each pulling 2.5 amps on a 24V DC system what size wire do I need to be running??

 

The total current would be 10*2.1A + 3*2.5A = 28.5A.
You'll need a lot of batteries if you want to run all those for 6 hours or more.
A standard car battery will run that for less than two hours.
That's a hefty current and you should use 7Ga wire for that, according to this table.
You could also use multiple strands of smaller wire based upon the listed current capacity, if that's easier.

 

right, my bad, I gave you the 12v amperage. So, that would be 1.125A on a 24V system for the 27 watt lights, and 1.25 for the 3 bars, right? 24V cuts the load in half? I was thinking it put me at 15A. Is my math off?

 

Why 24V to run 12V lamps? Are you putting the batteries in series with 2 parallel strings of x lamps in series?

 

right, my bad, I gave you the 12v amperage. So, that would be 1.125A on a 24V system for the 27 watt lights, and 1.25 for the 3 bars, right? 24V cuts the load in half? I was thinking it put me at 15A. Is my math off?

Somewhat.
You can run two lamps in series to operate from 24V to halve the total current, but you can't do that with the 3 bars.
You either need 2 bars or 4 bars to do that.

But note that running two batteries in series to give 24V won't run the lights any longer than running the batteries in parallel at 12V.

 

Right, and each pair of lights in series will need to be identical to achieve the rated power/brightness.

 

So, if maximum battery life is the goal, am I better splitting them in 2 different 12v systems?

 

So, if maximum battery life is the goal, am I better splitting them in 2 different 12v systems?

It essentially makes no difference as far as battery life.