Electronics, Lighting, & Gadgets - MR-16 LED lights for DIY light system

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clydesdale
10-29-08, 10:54 PM
Has anybody tried these new LED lights that come in a MR-16 body? I am thinking of trading out my lights to lower the power consumption and hopefully the size of the sld battery. I just got a 15 degree angle 3x1watt LED MR-16 light from ebay today. I have measured my housing and i think they may fit. Right now I have 2x 20 watt halogen bulbs in they are floods (as it is hard to find spots in the local market). They do not throw light as far as i would like. They do light it up though but for any speed over 20mph the halogens do not throw light far enough up the road.

So Questions:
If you have tried these in your home brew what do you think of them?
Do they throw enough light?
Do you think a 3 ah will give me a run time of about 6 hours if i am running two of these? If not what size battery would? I can not efford the fancy light batteries has to be SLD.:mad:

MNBiker
10-29-08, 11:47 PM
clydesdale,
I'm no electrical engineer but here's my understanding of batteries and capacity:
A 3 ah (amp-hour) battery will theoretically put out, for example, 1 amp continuously for three hours. The (number of amps being consumed) x (number of hours running) = amp-hours.

If I understand you correctly one LED light fixture consumes 3 watts. So running two would use 6 watts. The formula for watts (learned in 7th grade electrical shop class) is Amps x Volts = Watts. So doing some algebra, Watts divided by Volts = Amps being consumed.

If your LED's run on a 12 volt battery you get 6 watts divided by 12 volts = 1/2 amp. A 3 ah battery would theoretically run 1/2 amp for up to 6 hours, but in reality I don't think you can practically get that much use out the the battery to have it run with adequate power. So I would guess it might practically run for 2/3 of the theoretical time which would be for 4 hours

What you would need to know is how many volts do the LED's take when running. You need to know this anyway to get an SLA (sealed lead acid) battery of the right voltage. I hope my thinking has been helpful.

David

Map tester
10-30-08, 10:36 AM

I have been using 12v MR16 LED bulbs for years. I usually use a sealed lead acid battery, with about 5 Ahr rating. I can at least 2 hours runtime, but haven't pushed it past that--SLA don't take being run to low very well.

djwright
11-01-08, 05:44 PM
I just got a 15 degree angle 3x1watt LED MR-16 light from ebay today. I have measured my housing and i think they may fit. Right now I have 2x 20 watt halogen bulbs in they are floods (as it is hard to find spots in the local market). They do not throw light as far as i would like. They do light it up though but for any speed over 20mph the halogens do not throw light far enough up the road.

The beam angle on the halogens makes a big difference. I bought a 10 degree 37W MR16 bulb made by GE. That thing is flat out bright. But my 20W spot is also pretty bright. So if you want to upgrade those tyr shopping online.

clydesdale
11-01-08, 06:19 PM
It is not about the throw as much as the size of battery I have to carry. I know if i could loose the wieght of the battery in body fat it will all work out. Man 5 pounds is alot to loose Haha:lol:

djwright
11-02-08, 01:33 AM
It is not about the throw as much as the size of battery I have to carry. I know if i could loose the wieght of the battery in body fat it will all work out. Man 5 pounds is alot to loose Haha:lol:

I went with the SLA battery and because they are cheap I bought two. so i have one at work and a charger. So the battery only has to last one way. That helps keep the battery weight down. (mine is only 4.2 pounds).

For me a 5 pound weight loss is just a start.

clydesdale
11-04-08, 11:53 AM
The mr16 led light came in last night. I put it on and rode around the block. The street lights washed it out a little bit, but no more than the halogens. I went with a warm white. I am now think I should have gone with the white instead. So now I am looking for a white flood led for the other housing. Does anyone recommend any one. I do not think i want more than 40 degree angle. I am wondering about 25 degrees seems to be better.

djwright
11-17-08, 06:47 PM
The mr16 led light came in last night. I put it on and rode around the block. The street lights washed it out a little bit, but no more than the halogens. I went with a warm white. I am now think I should have gone with the white instead. So now I am looking for a white flood led for the other housing. Does anyone recommend any one. I do not think i want more than 40 degree angle. I am wondering about 25 degrees seems to be better.

So which LED bulb did you end up getting?

clydesdale
11-17-08, 07:55 PM
I went with a warm white 15 degree spot and a white 38 degree flood. I love the white hate the warm. They are from a dealer on ebay called LED wholesalers Just type in mr16 led and you will see them. They cost about \$33 each but i can now have roughly 4x the run time with more light. I have not tested them fully yet. I will post pics and a full report on them after I test them more.

bikinfool
11-17-08, 10:04 PM
Thread caught my eye as I've considered trying some MR16 LED fixtures in my old Nightsuns. In looking around didn't find that the commercially available stuff was getting good reports (vs going DIY with an LED kit like Cutter offers). My batteries were originally Nicads, wouldn't even consider SLA, but I did want to reduce weight. I'm experimenting with overvolting the 12v MR16 halogens with a 13.2V Nimh battery, so far so good but just starting...MR16 halogen bulbs are cheap.

Zekat
11-20-08, 06:36 PM
I've been happily running a 3W "cool white" MR16 LED for about two years now. \$16 from autolumination.com (http://autolumination.com/home.htm), search for "MR16 12 Volt Super High Powered 3 Watt Luxeon LED".

I paired it with a 20W halogen 10-degree spot bulb (\$9 for 3 at Lowes). While the 3W LED is not as bright as the halogen, I find myself rarely using the halogen for seeing; usually I just use it for wet asphalt or attracting drivers' attention. Yesterday yet-another oncoming cyclist (on the other side of a 4-lane road) shouted "whoa that light's bright," but YMMV. ;)

Two years ago I measured the current draw (with the xenon strobe tail-light) around 400mA, IIRC, so I generally figure about 2 hours runtime per usable battery Amp-hour. (Apply lead-acid battery low temperature de-rating as needed. Nickle based batteries are supposedly exothermic on discharge, so they're a better choice for cold climates).

Running two of these 12V, 3W LED's gives 6W. P = V * I, so I = P / V; so I = 6W / 12V = 1/2 A, so 6 hours requires 3 (usable) Ah of battery capacity. I have been using a 7Ah SLA and figure I have at most 3.5 usable Ah in the cold Minnesota winters. Also keep in mind that SLA supposedly don't like being fully discharged, so don't do that. :)

clydesdale
11-20-08, 11:19 PM
When I used the 20 watt halogens I could run one for 1 hour with out any noticeable dimming. If i used the second one as needed to give more light i could notice the light dimming real bad in 40 mins. This using a 5ah battery in Denver during winter. I figured rough math 20/6=3.3 so in theory I should be able to get at least 3hrs run time.

Zekat
11-21-08, 03:53 AM
Battery capacity is kind of a funny thing; the Amp-hour rating is typically for a current small enough to take 20 hours to fully discharge (the so-called C/20 rate, where C is capacity). Supposedly that Ah rating goes down as the load current rises.

The general rule-of-thumb I still remember (I did all the research two years ago) was size the SLA for twice the expected average current multiplied by the desired run time, and keep the voltage above 2V per cell (this means a 12V SLA is "fully discharged" at 12.0V and you may drastically shorten the number of discharge/recharge cycles by discharging it to lower voltages).

http://www.batteryuniversity.com/ has all kinds of interesting stuff about care & feeding of batteries.