Led Par Cans on Battery

[fatfrog]

I have been asked if I can provide a client with a battery powered LED rig for a float for a festival, As the cart is being pulled by a horse there is no genset on board so I need to arrange a battery powered solution.

 

The can's I have available are the following:

 

Clicky

 

I believe they have a step down transformer inside anyways so I believe all I have to do is disconnect the PCB from the transformer and connect it to the the battery supply instead provided it is appropriate voltage.

 

Can anyone confirm this for me.

 

Cheers.

[JDP]

The problem is the battery reliability.

 

As your pulling hardly any current with LEDs, why not use a car battery and an inverter? Still battery, but seemingly more reliable.

[matt c]

A bit of advice from the electronics side...

 

If I was you, I'd measure the maximum current draw from the lamp with a multimeter / clampmeter (if you have one). Or find a datasheet and see if it says the power or current and voltage required. Then go to Maplins, or some such, and make a small regulator. Fixed voltage 2A regulators are pretty damned cheap, less than a quid, and I'm fairly sure 2A would be enough. Get some flat backed heatsink, and a few capacitors, and it'll present a nice steady voltage to your LED PAR cans, regardless of the battery voltage (bearing in mind a fully charged lead-acid battery is 13.7V, I think). Depending on what's in the lamp, you may also need a +5V rail for the DMX controller side of it.

 

If it's worth your while, you could consider converting the lamp to 12VDC, permanently building the circuitry into the lamp itself, replacing the existing power supply.

 

Matt

[Jivemaster]

As the warranty expires as you alter the LED cans, the inverter could be your friend.

 

Get a car jump start battery from Maplin and use a 150 or 300w inverter to drive a few cans. Control may be a challenge as there will be no earth connection so DMX may be less stable than you desire. These batteries are 17AmpHour and well suited to rapid discharge. -Start calculating Ahrs vs time vs unit efficiency etc.

 

 

If you don't bother about warranty then open the can and look, then measure. See if you can find a point on the cct where you can substitute a battery for the PSU if your electronics skill is up to standard.

 

Look also at Maplin and B&Q for wxterior LED lighting kits BUT these can be 12v AC so bring their own problems

[gyro_gearloose]

To be honest, it'll be a lot of faffing about chopping the electronics up to run then cans off a battery. You'd only have to convert them back to run off a mains supply when you want to use them for another job.

 

Get yourself an inverter and run it off a few car batteries wired in parallel. This will give you more Amp/hours to play with, but you must use diodes or bridge rectifiers to connect your batteries together. These will prevent one battery from reverse-charging the other if one one battery runs out before the other.

 

The easiest way of doing this would be to get yourself a bridge rectifier. It will have four terminals marked '+', '-', and two with '~'. Connect the '+' from one battery to one '~', and the other batteries '+' to the other '~'. Now take the '+' terminal from the rectifier to the positive terminal on the inverter. Join both batteries '-' terminals and connect them to the inverters '-'. Leave the '-' on the rectifier un-connected for now, we'll get to it in a bit. It might be worthwhile to add a fuse to the positive lead between the rectifier and inverter.

 

If you want to charge both batteries just connect the positive lead from the charger to the '-' terminal on the rectifier and the negative lead to the batteries negative terminals, leaving the rectifier in place. This will charge both batteries from one charger.

[KidRay]

Just wondering, presumably this is a daytime event, in which case you won't see much from LED parcans. You may see the colours if you are staring directly at the fixtures, but even standard parcans struggle against the big light in the sky...

Just thought I'd mention it before you spend too much time/money.

[dunk]

A car invertor is a good idea. Alternatively, use a UPS, (Uninterruptable power supply), often found on server racks, etc. You will get loads of run time from led cans as they pull bugger all!

 

Dunc

[Russ83]

Try and get hold of a couple of leisure batteries rated at 85Ah or above. Over here I get them from a motor/caravan shop for £55 each. These are designed to be discharged regularly rather than standard car batteries which are meant to be constantly topped up. Also the voltage doesn't drop off as quickly as the battery discharges.

 

If your batch of LED pars are like mine then you will be pulling your hair out trying to get inside them all and then put them back together. All the nuts drop inside when you unscrew them! I would therefore recommend using an inverter.

 

A UPS would work for a short period of time but I think you'll find that all the internal cooling fans will probably use more power than the Pars.

[Rob]

Event concept in South London do have some battery powered LED uplighters but they'll probably be quite expensive and don't have any hanging hardware.

[Ekij]

Small car battery inverters often have really bad 'sine' wave approximation.

Some are even a square wave.

They often assume they are powering a kettle or other resistive load directly that won't care.

The transformers in your LEDCans might not mind this, and then again they might.

 

Using the voltage regulator won't work too well as most of these need a 1.5 or 2V drop between the voltage in and regulated voltage so your "12V" battery will only provide the regulator with >=13.5V for a small time before it's terminal voltage drops to the power where the regulator can't maintain 12V anymore.

Once again your LEDCans might or might not get upset if their 12V supply drops off.

Probably what you will see is colour shift as the Blue and Green dim faster than the Red with dropping rail voltage.

[matt c]

Using the voltage regulator won't work too well as most of these need a 1.5 or 2V drop between the voltage in and regulated voltage so your "12V" battery will only provide the regulator with >=13.5V for a small time before it's terminal voltage drops to the power where the regulator can't maintain 12V anymore.

Once again your LEDCans might or might not get upset if their 12V supply drops off.

Probably what you will see is colour shift as the Blue and Green dim faster than the Red with dropping rail voltage.

 

Hadn't thought of that.

 

Of course, you could always use a +12V and a -5V regulator. Use the 0V line to supply 5V (relative to the -5V rail) to the DMX side of things, if required, and use a standard 12V reg with the ground leg tied to the -5V rail. Maximum input PD is then about 19V, so a standard reg should easily be able to cope. Just need to make sure that the -5V reg can handle all the current.

 

Matt.

[Tomo]

Using the voltage regulator won't work too well as most of these need a 1.5 or 2V drop between the voltage in and regulated voltage so your "12V" battery will only provide the regulator with >=13.5V for a small time before it's terminal voltage drops to the power where the regulator can't maintain 12V anymore.

Or just use a series pair of 12V car batteries followed by a big 12VDC regulator. Heck, a bank of 7812s would probably cope - don't try to run everything from one of 'em though...

 

For control, SmartFade and SmartFade ML have been successfully run directly from 12V car batteries - they don't care about the slight overvolt or undervolt from a discharging battery.

 

The Arcola Theatre has been running a few shows purely from hydrogen fuel cells and batteries for a while now - it may be worth contacting them and seeing if they have any suggestions.

[adam2]

I would use a car battery, or better a leisure battery since as others point these are more suited to deep discharge.

To power the PAR cans I would use a sine wave invertor.

As others point out, the cheaper invertors have a square wave output which may not be suitable for use with electronics.

I would advise against trying to convert the PAR cans to a DC supply since the voltage may be wrong, are you certain that they use 12 volts internally and not some other DC voltage?

 

As others point out, useing a 12 volt regulator from a nominal 12 volt battery wont work since the regulator requires at least a volt or two accross it, which wont be available.

 

Connecting batteries in parralell via bridge rectifiers wont work, the on load voltage drop of a bridge rectifier is about 1.8 volts, this will reduce the input to the invertor to about 10 volts, most have a low battery cut out that prevents operation if the input drops below about 10.5 volts.

 

Lead acid batteries may be connected in parralell provided they are of the same nominal voltage and are at a similar state of charge when connected.

(long term parralell operation is unwise unless the batteries are of the same brand, age, and capacity, however for short term use I would not worry)

[Mark M]

Rather than start a fresh topic I thought I would ask in this one as its very similar. I only need to light a single LED can, is there any small batteries which would do this job?

 

Edit- dont need any control, will run fine on auto for this application.

[paulears]

I guess the comments haven't changed - Yes - you can do it - but you still have to convert the 13.8V from your battery to whatever power supply rail your own can uses. This means pulling it apart, disconnecting the PSU internally, then replacing it with your own version. If it's an old LED device, then this shouldn't be a problem - but to be honest rather depends on how good your soldering skills are.