6V reflector lamps

[Tom Baldwin]

I need to create, in effect, a hand held birdie. In order to reduce the weight of batteries that the actor needs to carry, I'd like to use a 6V MR16 or MR11 lamp. 50W, about 40' beam angle.

 

I've failed to find anything this powerful in 6V so far, but wondered if any BRers had a secret source of supply for odd lamps?

 

Failing that, I guess I'm going to need a voltage doubler...

 

Cheers,

 

Tom

 

P.S. I could, I suppose, use twice the number of AA cells as D cells and fit it into the available space that way, but that's going to push the running cost up quite a lot.

[Brian]

Type EFM aka A1/229/6847 is an 8v MR16 50W

Type GBG aka Philips 6229 is a 6v 56mm dia 35W but is 4 degrees

 

You could always take a standard MR16 and carefully remove the lamp and replace it with a 6v capsule lamp.

[Tomo]

From an efficiency point of view, you'd be better off using the 12v lamps from a 12v battery, because you need a lower capacity battery to supply the same amount of energy and resistive losses are lower.

 

Exactly what batteries you choose depends on how long your run is, and how long the lamp has to be lit.

 

If the run is short, then dry-cell alkalines (eg Procell, Duracell etc) are your best bet, changing them whenever the lamp starts to get noticably dimmer.

 

Once you've got a few nights, I'd suggest a Sealed Lead-Acid battery (note: NOT liquid electrolyte) and suitable charger, charging it after every performance.

They are available in 2v, 6v and 12v units, with capacities ranging from around 0.5Ah up to 'very large'.

 

The capacity you choose depends on how long the lamp needs to be lit each night.

It's measured in Amp-hours. A capacity of 1Ah means that the battery will supply 1A for 1 hour, or half an amp for 2 hours, or 2A for half an hour etc

 

In theory at least - in practice you usually have to derate by a few % for 'large' currents (large being defined by the cell design).

I normally derate by 10% except in exceptional circumstances.

 

50W at 12v is a current of 4.2 A

50W at 6v is a current of 8.4 A

 

(For your information, an alkaline D-cell is about 13Ah, and an AA cell is about 2.4Ah. For use calculations I'd derate by about 15-20%, as the discharge curve isn't very flat.)

[Guest lightnix]

PM sent with alternative suggestion.

[Jivemaster]

theres the pinspot lamp 6v 30w par 36 narrow beam though, look into Ni-MH batteries from maplin or the like AA Ni-MH is about 2ah all depends on the "on time"and the run tho.

[Tom Baldwin]

Thanks to everyone for the suggestions - Brian, in particular your suggestions lead me on to some other very interesting ideas, one of which is the slightly scary DWH/DWJ PAR36 medium flood - 6.3V, 100W and three hour life!

 

I've still not finalised which way I'll go yet, but thought I'd share the resources I've found:

Very comprehensive reference to lamps: Don's Bulbs

Comprehensive reference to batteries (surprising how hard it is to find capacity data out there...: House of Batteries

 

I already knew that pushing batteries hard meant you wouldn't get so much out of them, but I was amazed to find out how much - Kodak provide some interesting discharge curves for their batteries, for example - even trying to draw 4A from a D cell (19Ah) is pretty much a non starter - once you get past an amp or two, the service life tends asymptoticallly to zero... I would go for lead acid, but the cost of the batteries, plus the proper charger, puts the prop a bit out of budget.

 

Having seen a 225V (yes) battery at House of Batteries, I might just use that and a GU10 mains dichroic...

[Jivemaster]

12v 55w used to discharge prime quality D size nicads in an application of mine overly fast. Look at quality D or F size nicads or Ni-maetal hydride cells.

 

OR dump fillament lamps there are reflector compact fluorescents and small assemblies of LEDs to be more power efficient.

[Tomo]

I would go for lead acid, but the cost of the batteries, plus the proper charger, puts the prop a bit out of budget.

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Compared to the cost of dry cells that's not the case.

You can get a small (4Ah or so) 12v SLA for about £12-£15, and a cheap charger (no end-of-charge detection) is about £20.

That will run a 50W lamp for about 45 minutes.

 

Using D cells (£3 a pair) you're looking at one (maybe two) sets every night - £12 a 12v set, once you have three nights it's cheaper.

 

However, if you can live with the slight lack of colour consistency across the beam a set of white LEDs is probably better.

[Ike]

You could always take a standard MR16 and carefully remove the lamp and replace it with a 6v capsule lamp.

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...or LED(s)