Power Where No Power Can Go

[bishopthomas]

I have just been asked to provide a truss structure and lighting for a banner on a barge. No big deal, right? Well, this barge will be in the middle of the river. Getting more complicated... There can be no generator because a massive fireworks show will be shot from the barge. Now, before you recommend battery powered LED's know I've thought of that but prefer to use my own LED's (140w) in order to actually make money on this gig.

I'm thinking about using car batteries and inverters but know absolutely nothing about this type of setup. I'm not sure exactly how long I need to be powering the LED's but I do know that once it gets dark enough to shoot fireworks they do so, then the show's over. So figure at most an hour before the fireworks, a 30-45 minute show, then maybe 30 minutes "postshow." Plus I'll need a little extra juice for testing purposes. So let's say a minimum of 2.5 hrs.

Anyone have any suggestions, advice, alternatives, etc?

 

[rochem]

EDIT: I assumed a powered barge, instead of an unpowered one. Never mind.

 

[cpf]

Extension cords, duct tape, and lots of cheap fishing floats?

 

[bishopthomas]

I did think of buying 1000' of SJOOW cable and running two circuits from shore. I'd rather keep it all on the ship, though, so cabling it is last resort.

 

[avkid]

How many units?

 

[chausman]

Bicycle? Someone looking for something to do for 2.5 hours? Advice...more batteries than you think you will need. And make sure no one else uses your battery power.

 

[shiben]

Bicycle? Someone looking for something to do for 2.5 hours? Advice...more batteries than you think you will need. And make sure no one else uses your battery power.

I feel like whatever parks the barge and holds it in its position should have some way to power things.

 

[techieman33]

A couple of big UPS's would do the job too.

 

[shiben]

A couple of big UPS's would do the job too.

This is essentially some car batteries, inverter and transformer. Obviously its a bit more complex than that, but the means is pretty similar.

 

[LXPlot]

I feel like car batteries won't be able to produce enough voltage to power your LEDs (they're 12 volts). You could try using a transformer, but I feel this would cut the amperage to low.

If you get an inverter, you most definitely need the "Pure Sine Wave" kind.

I'm not sure whether (a) UPS(es) would work because of the pure length of time that power needs to be created.

What about using some sort of solar generator? I don't know how much electricity they produce, or how much they can hold, but if it's enough that you could reasonably continue to use it after dark during your performance, and your 140w LEDs could survive on this, that might be the way to go.

Although I'm really surprised that the barge doesn't even have a little bit of built-in power.

 

[xander]

I did think of buying 1000' of SJOOW cable and running two circuits from shore. I'd rather keep it all on the ship, though, so cabling it is last resort.

If by any chance you are talking about the July 4th fireworks on the Hudson, then I have a feeling cabling to shore is out of the question. But, on the plus side, if you are talking about this event, all of the barges have a tug keeping them in position and you should be able to get your power from them.

 

[JD]

If not a tug, what about a small boat in tow with a generator? Keeps it off the main barge.

 

[avkid]

There's no way you're making money on this if you need to build your own power.
You're looking at about $450 for 4 deep cycle batteries and least that much for a good inverter add in cabling you're quickly north of $1K.

By rough calculations you'll get an hour out of 4 batteries.
This is 4 (four) group 27NF deep cycle batteries.

 

[sk8rsdad]

Let's make a few rash assumptions, like your LEDs are going to be happy working off an inverter. This is all rough numbers with rounding up.

140W at 12V requires about 12 amps of current. That means that given 100% efficiency you would need a 12aH (amp-hour) battery to run for 1 hour. Assuming an inverter with about 80% efficiency, you need about 40aH (amp-hour) 12V battery to achieve 2.5 hours of run time. If you're willing to bodge something together you ought to be able to do this with a single car battery and a cheap inverter, or a similarly rated UPS.

 

[sarahsliefie]

You would need a ton of car batteries to make this work I did a float last year with all the testing I did before hand I could run 2-100W lamps on one battery for 45 minutes. By the end there were at about 60% though. You could connect 2-3 batteries up to increase that time but keep in ming as time goes on the voltage drops. Even with a good inverter this could be bad for the LED power supply. If there is no tug to connect to I would look at a cable first. There are so many things that could go wrong with batteries.

 

[drummerboi316]

Since this is a massive fireworks show, is it going to be electronically fired? or is it hand fired? Because if it's electronic, maybe you could jump off their power, or find out how they do it. But if not, it brings us back to square one....

 

[avkid]

You don't want to use regular car batteries with an inverter as they will not tolerate repeated discharge and recharge cycles.

 

[FatherMurphy]

To clear up a few misconceptions some of the above posters have been working from, based on my knowledge of pyro being shot from barges...

A barge is just an empty boat, often with a solid, flat top (especially if it's designed to carry things parked on top of it, like cranes). They don't have any kind of motor, engine, or battery system.

A barge is moved into position by a towboat, which has lots of power available, but only if the towboat stays with the barge during the shoot, which isn't always the case. Often a barge will be anchored midstream, or will have long poles driven down into the bottom to moor it, and in the event of a sudden rise in water level, or heavy weather, the barge can break loose and float away. Relying on tow boat power or cabling to shore can be chancy if things get rough.

The pyro will be fired by a battery system, but the shoot team won't be very interested in risking their show by using their batteries to power lighting. The firing system uses a lot less power than a lighting rig, and can include capacitors at the firing boxes by the racks that charge slowly during setup, and dump power rapidly during use, so the characteristics of their system are different than you might think. It doesn't take much to ignite an electric match.

The preference for battery power is to remove a potential source of ignition from the fireworks shoot site, for obvious reasons.

The main courses open are to use battery/inverter systems, asking if the towboat will be staying with the barge, seeing if a small generator in a rowboat tied to the barge with 50' or 100' of rope will be far enough away for fire safety, or buying a pallet load of chemical glowsticks or LED flashlights.

You might be able to work something out with a battery store (or RV dealer) regarding borrowing/renting/sponsoring a battery rig. I'd either bite the bullet on the batteries/inverters, or try for the generator in the rowboat.

 

[zmb]

6 volt golf cart batteries (Don't know the number of amp-hours), 2 wired in series, then in 2 pairs in parallel plus one inverter can keep a desktop computer going for a while and could easily handle 140w of LEDs.

 

[BillESC]

Seems to me a generator sized to fit the load is a no brainer.