Running 4 x 50W bubbles from battery

[pocasluces]

Hello,

Any idea which battery would be the best to run a total of 4 x 12V 50W Bubbles for a total of 2 hours?. The reason for this is to create an effective lighting source that it can be moved around the stage by the actors. The battery will rest on a base with wheels. On the same base it will be a stand for the lights. Also I would like to know if 12w 26W flourescent lights could be run from the same battery?

 

Thanks

[dbuckley]

200W of incandescent at 12 volts is about 17 amps, so you need about 17 amp/hours of juice per hour, so capacity needed is 35 amp/hours. But.... to get anything like the rated amp/hours out of a battery you need to not exceed one twentieth of the amp/hours per hour. So, 20 x 17 is 340, so you want a 340 AH deep cycle (sometimes called marine, or leisure) battery (or batteries in parallel to that amp hours). Adding the 26W fluoro wont make a difference to the size needed.

 

However, if you look at the battery manufacturers tables, they often quote accelerated discharge figures, that deliver a a lot less than the rated amp/hour but will do what you need.

 

Fore example, Trojan 24AGM 76AH battery (at 20 hour rate) is rated to last for 137 minutes at 25A. That's only 57AH, but you don't care; 17 amps for two hours is what you need, and for a while, that battery should deliver it.

 

The good news is the battery weight will keep the thing from falling over :)

[paulears]

In panto this year, we had two trucks, each with 2 x 50W birdies inside. Scene length about 10 minutes. 2 brand new batteries sourced from the local Kwik-Fit. The ASM mentioned what they were for and they wouldn't sell them! In the end, we endorsed the guarantee with a note accepting we were using them against the recommendation of Kwik-Fit, which I though was a little over the top. However, we ended up charging between Matinee and Evening shows, then again overnight. By the end of the last show in the run (88) they were both doing a gentle fade out before the scene end - which luckily didn't matter. On paper that's a current of just over 8 Amps and that left them struggling. Leisure batteries would be the ideal thing to use. I wonder, based on the small size of modern car batteries compared to old ones, if their design has become optimised for starter motor use, then quick recharge, then low drain. It must be something like this as the amp/hour figures don't seem to relate to their actual capability any longer?

[timtheenchanteruk]

car batteries have indeed changed their design, rather than a one fits all, they are deigned to the car (or cars requirements) so a small engined car only needs a piddly battery to start it.

 

Car batteries are also designed to give all their power at one, then re-charge . leisure batteries are more expensive, but have thicker plates (so weigh more) to compensate for the slower drain/recharge.

The ideal battery would be a traction battery, designed to give out power over a very long period at constant draw, however these cost quite a bit more than leisure batteries.

 

the AGM is a glass matt design, very expensive, and you need a special charger for them, upside is that they can be used on their side/upside down/whatever you want to do with them.

 

fast charging a leisure, traction or AGM mat without a specialised charger is the best way to kill them.

[musht]

Car batteries have thin plates optimised for delivefring large current for short time, starter can take impulse of several hundred amps on a disesel.

 

Deep disharge kills them quickly.

 

Leisure or deep cycle batteries as explained have thicker plates to allow deep discharge without plate warp or excessive sulphating.

Marine and caravan suppliers or a decent motor factor , never Kwik-Fit, to be fair good advice in this case, even if it is for a car.

 

Traction batteries are 3 times cost of leisure batteries and weigh as if they are made of plutonium but are the ultimate in portable power from lead acid.

[dmxtothemax]

Perhaps it would be easier to use 12v compact floros,

They use a lot less power,

So a smaller cheaper battery would be required.

 

Finding a battery to supply 200w per hour for 2 hours,

Is possible but likely to be expensive.

 

Why dont you get a hold of a car battery, charge it up,

then see how long it lasts with the 200w load.

You might be supprised,

What works in theory and what works in reality,

Not always the same thing.

 

Hello,

Any idea which battery would be the best to run a total of 4 x 12V 50W Bubbles for a total of 2 hours?. The reason for this is to create an effective lighting source that it can be moved around the stage by the actors. The battery will rest on a base with wheels. On the same base it will be a stand for the lights. Also I would like to know if 12w 26W flourescent lights could be run from the same battery?

 

Thanks

[dbuckley]

car batteries have indeed changed their design, rather than a one fits all, they are deigned to the car (or cars requirements) so a small engined car only needs a piddly battery to start it.

Indeedy.

 

Car batteries today are typically not rated for amp/hors, but for CCA - Cold Cranking Amps, which is the current the thing will put out for a short period of time when its really cold. My SUV has about a 700 CCA battery...

[pocasluces]

Hello again, Thanks for the advice.

Based on the replies, I managed to get a 60Ah car battery. Since I am in Brazil, it was not that difficult to find an old car battery :) . Next I will just run a test with the actual load (4x 12V/50W). The weight of the battery is not too bad, good thing is that it will save me some money in stage weights!. Depending on the result from the test, I will make a final decision on whether I use the 12V/50W bubbles or I go for the save option of using the 12v/26W flourescents. I am hoping the battery will be able to take the bubbles, as I like more the more spot feeling from them.

If anyone is interested on the results from the test, I can keep you update.

 

Thanks

[adam2]

As others post it is certainly possible to work 4 lamps each of 12 volt, 50 watt from a 12 volt battery, but will need a very large battery.

The load is indeed about 17 amps, which allowing for the poor performance of lead acid batteries if discharged quickly, suggests a battery of least 70 A/H and preferably more.

In practice a single deep cycle 70 or 80 A/H battery would probably suffice, and these can be obtained to order from most garages etc.

 

It might be better to use higher efficiency lamps.

If a directional light is not needed then consider 12 volt CFLs. 4 lamps each of 11 watts would only use about 4 amps, suggesting that a 17 A/H battery might just suffice, or a larger one to give a margin.

 

If directional lighting is needed, then perhaps consider 12 volt, 5watt LED MR16s.

4 such lamps would use less than 2 amps, and a 7 A/H battery might just suffice, though a bit bigger would be better.

For a good light, top qaulity LED MR 16s will be needed, at about £17 each. The cheap ones give a very meagre light.

 

Take great care with batteries, they are allways live and deliver hundreds or even thousands of amps if shorted.

Anything connected to a battery should be protected by a fuse as close to the battery as possible.

For LED /CFL I would put all 4 lamps on a 10 amp fuse.

For 50 watt halogens I would put two lamps on each circuit, with a 10 or 13 amp fuse for each pair of lamps.

[church]

Car batteries have thin plates optimised for delivefring large current for short time, starter can take impulse of several hundred amps on a disesel.

 

Deep disharge kills them quickly.

 

Leisure or deep cycle batteries as explained have thicker plates to allow deep discharge without plate warp or excessive sulphating.

Marine and caravan suppliers or a decent motor factor , never Kwik-Fit, to be fair good advice in this case, even if it is for a car.

 

Traction batteries are 3 times cost of leisure batteries and weigh as if they are made of plutonium but are the ultimate in portable power from lead acid.

 

 

Err!! I think you mean they are made from platinum

[dmxtothemax]

Yes please! let us know how you go.

 

Hello again, Thanks for the advice.

Based on the replies, I managed to get a 60Ah car battery. Since I am in Brazil, it was not that difficult to find an old car battery :D . Next I will just run a test with the actual load (4x 12V/50W). The weight of the battery is not too bad, good thing is that it will save me some money in stage weights!. Depending on the result from the test, I will make a final decision on whether I use the 12V/50W bubbles or I go for the save option of using the 12v/26W flourescents. I am hoping the battery will be able to take the bubbles, as I like more the more spot feeling from them.

If anyone is interested on the results from the test, I can keep you update.

 

Thanks

[musht]

Car batteries have thin plates optimised for delivefring large current for short time, starter can take impulse of several hundred amps on a disesel.

 

Traction batteries are 3 times cost of leisure batteries and weigh as if they are made of plutonium but are the ultimate in portable power from lead acid.

 

 

Err!! I think you mean they are made from platinum

 

Actually think meant depleted uranium , to express how incrediblly heavy for their size they are. Not that they contain any MrFusion type flux capacitors ;-)