Author Topic: Converting a Halogen floodlight to LED  (Read 459 times)

Offline Spires

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Converting a Halogen floodlight to LED
« on: July 03, 2019, 10:26:25 pm »
Hi Guys,
I have been thinking about getting my defunct hand-held floodlight (Halogen bulb, 12v, 100w, 3.5 million candle-power, large diameter reflector: 16.5cm/6.5 ins, Yellow body) converted to LED, or would it just be easier/cheaper to purchase a new LED floodlight? I have viewed a couple of similar floodlights today on 'Amazon', priced around £26. The dimensions of one of the floodlights was smaller than mine, with an (approx) 4 ins diameter reflector. The floodlight would be used for illuminating deep mine shafts and mines & caves, containing large passages & caverns. Your thoughts please. Many thanks, Paul.

Offline Madness

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Re: Converting a Halogen floodlight to LED
« Reply #1 on: July 04, 2019, 08:07:41 am »
I doubt that the design of the reflector will lend itself to working very well with an LED.

Also an LED producing a lot of light also produces a lot of heat. That heat has to be dissipated into the body, which I assume in the case of your lamp is plastic.

In all honesty I'd just buy myself a new handheld torch from China.

A while ago I posted a thread with a link to a spreadsheet that has hyperlinks to beamshots. It's quite useful in getting an idea of what you might want. The Budget Light Forum is also another useful place for reviews and information on modifying lights.


Offline grahams

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Re: Converting a Halogen floodlight to LED
« Reply #2 on: July 04, 2019, 12:04:21 pm »
The cheap Chinese hand torches can be pretty good although they usually produce a tight beam - that may be what you want for deep mineshafts but will not be much use in large caverns where a wide beam is better. The one I have is rated at 10,000 lumens (Yes I know!). It is extremely bright but is faulty as it drains the batteries when turned off.

Apart from potential faults and the possibility of the cheap Chinese batteries exploding, check the colour temperature. One of my cheap torches, which I usually use to illuminate water from beneath, is so blue that it is difficult to correct in Photoshop.

It might be better to go for a mid-priced option such as MagicShine bike lights. These produce an even. wide beamed white light which is excellent for photography. The company has a good selection of headlight mounts which work well on caving helmets though the lights are not robust enough for anything beyond easy caving.

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Offline Chocolate fireguard

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Re: Converting a Halogen floodlight to LED
« Reply #3 on: July 04, 2019, 07:26:02 pm »
The luminous efficacy of halogen bulbs is generally given as around 20 lumens/watt, meaning your lamp would have been producing about 2000 lumens.

Given that and the 3.5 million candlepower, my sums suggest that the beam would have been very tight – something like a 1 metre diameter spot at a distance of 35 to 40 metres. Great for looking down mineshafts.

I doubt you can marry up your existing setup with an led to give you the same thing, so I imagine you are going to have to lash out on something new.

Manufacturers give the number of lumens, but generally not enough information to work out beam angle – “a range of 359 metres” (not 358! not 360!) is typical of what you get.

My suggestion is that you contact reputable manufacturers (the people who make LED LENSER come to mind but I am sure there are others) and ask for precise information.

I think you will be paying a bit more than £26 to get something that will do what your old floodlight did. 

Offline Madness

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Re: Converting a Halogen floodlight to LED
« Reply #4 on: July 04, 2019, 09:56:44 pm »
Be aware that when range is quoted for a torch, that is the absolute range that it can throw light to and it is a theoretical calculation and not an accurate measurement (I think!) Actual usable range is much less, probably about 2/3 or even less.

If you look at the spreadsheet I've linked to above you'll see lumens and range quoted, but what is really useful are the outdoor beam shots.