Led downlights equivalent to 20w halogen advice welcomed

[Walterk]

Naturally, thinking of going Led. Although I understand most parts of Led, I can not make up my mind and choose what to use.
So, any advice and experiences welcomed !

Especially links to products that proved to be adequate from real life experience are much appreciated. (There is a lot to buy, but hate to buy 9x wrong and to find the 10-th to be almost what I look for.)

I have 10 x 20 Watt Halogen downlights, on 3 switches, powered by DC converter/24-27v batterys, parallel with different cable-length up to 8 metre with 18awg/1,5mm2 crossection. Two string have PWM-dimmers (means regulation on voltage I think ?) on them. I am hesitant to alter the wiring, but I could put a variable current regulator in place of the pwm-dimmers.
The existing G4-fixtures are rear-pins with frosted glass window. They are well ventilated.

The to-be colour-temperature should be bulb-like. (3200-4000? )

Options:
- build a Led-replacement, not preffered, capable when good solution is at resourced, not interested in endless experimenting.
- find a suitable G4 Led-replacement, valued-by-experience products appreciated.
- replace fixtures with non-G4 and use Led-replacements that have good credits.

Please help ! :wave:

Edit: Info on why it is difficult to find led-replacements http://boingboing.net/2009/10/23/leds-throwing.html

 

[alpg88]

i found that 9w 3xre mr16 led bulb is similar in output to 20w halogen (advertisement says it replaces 50w, but it is b.s. it is not close to 50w halogen in output.
i would say 8-10w led bulbs would be as bright as 20w halogens, on paper it is not the case, but in real life, it is, i guess because those lights aren't driven to the max, due to heat issues, and optic loses..ect.
all mr16 are g5,3 not g4 mr11 are g4, but led mr11's aren't nearly as bright as led mr16, they are mostly small smd array,
as far as i know there is nothing off the shelf that is g4 and as bright as 20w halogen, and can run 24\7 with no heat issues.
also when i say as bright as halogen, i mean halogen is driven at 12v, not over driven to almost 20 as some do in flashlights, those are a lot brighter.

as for recommending you what bulbs to buy, search for 9w mr16 on ebay, you'll see plenty of results, you generally don't want to by all 10 unless you already tried one of the same bulbs, i noticed whatever sellers claim, most of the time is not the case, and sometimes not even close.
bulbs i bought came from orion led, from canada, i was looking for local sellers , but there are a lot more sellers from china that sell the same, and other bulbs, if delivery from china is ok for you, than order 1 to try , and than more if you like them, cuz you really have to see it for yourself, the tint, output, angle, quality, don't rely on anyone's word, cuz what is ok by them might not be ok by you, and vise versa.

 

[Walterk]

Thanks, thats good info.

So I understand I should look for something looking like 3x 3W-leds with in-build optics, to get equivalent 20W halogen ?
Makes sense, without optics the leds might have to little throw to hit the floor.
That won't ever fit within a average G4 fixture.

Another question, what would happen if I replace the PWM-dimmers to current-regulating-dimmers ?
I mean in case I have replacements with in-built regulator, and the differences in cable-length,would it have consequences for the output ?

 

[LEDninja]

Many LED bulbs have very narrow beam angles to compensate for the lack of brightness.
Check beam angle. The beams need to be overlapping by the time they reach tabletop level or you have a bunch of spots.

 

[Walterk]

Good point.

Thinking of using aspheric instead of glass window, and putting a Led close behind it. Afraid of the time and effort involved to find a apropriate formula of components.

 

[2010Steve]

Hi Walterk,

I agree with you on using aspheric instead of glass window. For led components, as my experience in halogen led replacements, I strongly recommend high power tri-chip smd led with wide angle beam. Currently there are some stores that sell g4 led replacements for your options:

Sales links removed

I believe you will find the appropriate led components for your halogen fixtures.
Good LUCK:nana:

sTeVe

 

[Walterk]

But how do you see multi-smd and aspheric lens happening giving a smooth spot?
That's not feasable except when you diffuse (meaning losses) inbetween led and aspheric.

 

[alpg88]

But how do you see multi-smd and aspheric lens happening ?
That's not feasable except when you diffuse (read losses) inbetween lens and aspheric.

i have 16smd mr16 with lens, it is flood, perfectly even pure flood, no hotspot whatsoever, but it doesn't come close to 20w halogen output, no smd mr16 bulb will, even with 5050 3chip leds. you'd need to go with par sized bulbs (but not par 20 cuz it is about the size of mr16), for more output, but par led bulbs for the most part are 120v ac, except for par36

i have cheap aspheric adjustable nebo flashlight, it has unknown to me led, and claimed to be 220lm no high, (i ran it on high for 1 hour straight, amaisningly not one spot anywehre on the flashlight became even warm), i can't say it is 220lm, but in flood mode it is a lot brighter than smd mr16 bulb

 

[qwertyydude]

If you have a light claiming 220 lumens and not getting warm you've got problems. The heat is being held in near the led's. No way you're getting 220 lumens from that Nebo light, which as far as I can tell is their "CSI" flood to throw 5 mode aspheric. Aspherics tend to waste a lot of light inside the head. You should measure the tailcap current. I know on most of my lights that run at 750 ma or so they'll get warm to the touch after 10 minutes or so and my 1 amp lights can actually get somewhat hot if you just set them on a counter on high.

Heat is bad for these led's and a high output led light that doesn't get warm is sure to shorten the life of its led. That's the big problem with these mr16 led conversions. You can't drive the led's to maximum output without burning them up. SMD style led's can never match the actual high power stuff. I bet when xp-g's and xm-l's get put into these finned mr16 lamps you'll easily be able to achieve the lumens required and be able to passively cool them at the same time because of the increased efficiency.

 

[alpg88]

If you have a light claiming 220 lumens and not getting warm you've got problems. The heat is being held in near the led's. No way you're getting 220 lumens from that Nebo light, which as far as I can tell is their "CSI" flood to throw 5 mode aspheric. Aspherics tend to waste a lot of light inside the head. You should measure the tailcap current. I know on most of my lights that run at 750 ma or so they'll get warm to the touch after 10 minutes or so and my 1 amp lights can actually get somewhat hot if you just set them on a counter on high.

.

posibly, but i don't care, it works, i paid 0 for it, (my job did) if it burns out, i get new one, lifespan is not my concern.

 

[Walterk]

Back on topic; how many Lumen would I be looking for.
Inverse square is not the way to get to numbers this time I think.

Now (with halogen) I measure 15 lux at floorlevel.