# Efficiency, Halogen vs. ordinary incandescent?



## Flummo (Aug 4, 2006)

How much more efficient is a 12V halogen bulb compared to a standard incandescent? 

I have a 40/45W (BA20D) 12V incan bulb, and I am wondering if a 35/35W (HS1) halogen would be brighter. Cant seem to find a ~45W halogen high & low beam lamp that would fit, but if the 35W should be at least as bright as the 45W standard lamp I'll try one.
http://www.donsbulbs.com/bulbs/g/ib/s1|12v|25w|25w|ba20d~ece.jpg


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## bfg9000 (Aug 4, 2006)

Halogen is not necessarily any more or less efficient. Just that at the same efficiency level, the halogen should last longer so manufacturers tend to drive them a little harder.


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## Flummo (Aug 4, 2006)

Ofcourse... Sometimes I seem to write faster than I think. 

Lets assume that both lamps are supposed to last the same time, what kind of diffrence in efficiency would you expect between them? I know that it is impossible give a exact answer, I'm just trying to figure out if it is something like 5% or 50%, or anything inbetween... I have found a comparison between a 20W "low voltage halogen" with 2000h life and 60 & 100W incandescent, the latter probably meaning ordinary 230V lamps with 1000h life. The 60W gives 12,1lm/w, the 100W gives 13,8lm/w and the halogen is up at 17,5 lm/w, meaning that the halogen is 45% and 27% more efficient. 

If 27% would be correct in my case, that would mean that a 35W halogen would be equal to my current 45W lamp, and if it's 45% that would give me equal to 51W with my current lamptype. The problem is that I don't think numbers for 230V 60/100W lamps is quite the same as for a 12V 35-45W lamp, so using numbers that don't apply to my lamp may end up making me very disappointed at the result (or the opposite, who knows).


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## Flummo (Aug 7, 2006)

I have spent some time searching for info on the web now. At http://en.wikipedia.org/wiki/Electric_light i found these numbers:

Incandescent: 12-17lm/w 1000-2500h life 2700K
Halogen: 16-23lm/w 3000-6000h life 3200K

If we assume that the two lamps I have in mind are about average of their kind, that would mean 14,5lm/w and 19,5lm/w, meaning that the halogen would be 34,5% more efficient and should give a little more light than the incan. And even if the halogen is less efficient than that it would be relatively easy to increase the voltage about 1V to 14V without sacrificing too much lamp life. I think I have heard that 5% higher voltage means about 20% more light and half the original life, and that light would be very welcome as long as the lamp life still is good enough.

Is this reasoning completely wrong, or is this a good enough reason to buy the lamp and try it?:huh2:


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## Ra (Aug 9, 2006)

Hi Flummo,

There is too wide a variation in halogens to give exact numbers, but if a 50 hour life is good enough for you halogens always have much higher efficiency !!

Example: The popular 24 volt 250 watt osram projection lamp produces 10,000 lumens !! So gives 40 lm/w (this is one of the extremes!)

I don't know of the 35/35watt HS1: If it is a (normal..) long life lamp the efficiency is much lower. But overdriving makes it more efficient, with lower lifspan ofcource !

Halogens are the better incandescents: In fact they are overdriven "normal" incandescents: The halogen cycle prevents the filament from evaporating by sending the evaporated molecules back to the hottest part of the lamp, the filament. The lifespan is only limited because of the "randomisity" (???) of this proces, causing variations in thickness of the filament-material, up till a part of the filament becomes too thin and melts..

So with halogens you can have about the same efficiency as with normal incan's but with a 4000h lifespan, or you can have much higher eff. with a 50h lifespan..

Two examples: From the Oriel catalog: 12v 50watt 3000h 850lum 17lm/w..

and.. 12v 50watt 50h 1600lum 32lm/w..

In general Halogen projection bulbs have 32-38 lm/w efficiency.

Regards,

Ra.


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## Flummo (Aug 9, 2006)

Okay, thanks for the reply! 50h life is a bit less than I had in mind, considering that the lamp is relatively expensive and it might be in use a few hours a day I an aiming for something more like a few hundred hours. If I'm not mistaking that is pretty normal for automotive lamps, I have read some .pdf about ordinary H4-lamps (wich are quite similar to the HS1, only wattage and a minor detail on the socket is diffrent) and if I remember it correctly they all were supposed to last 2-300h at 13,2 or 13,8V. 

I guess I'll give it a try, even if it isn't any better it is an excellent opportunity to use the lightsensor on my multimeter...


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