Just built LED light

[92se-r]

Don't know why many of you are using the CREE's when the K2 Luxeon's with TFFC are just as bright if not brighter. They are also 10X easier to work with and have a lower thermal resistance because you can use them without the star PCB. Lower thermal resistance = lower junction temp. which = longer life and more lumens.

Housing is inspired by scar on mtbr.com.







This picture was taken in a pitch black garage with no supplemental lighting. It is pouring rain right now so no outside shots. Sorry for the horrible mess in the garage. Too many projects and tools and too many hobbies.

360 lumens give or take powered by rechargeable AA's with 2-2.5 hours of run time. Way cheaper than your Niterider LED or L&M LED lights and just as bright.

My next revision will either have 3 or 4 LED's and a real battery pack. This was built as a budget helmet companion to my handlebar HID.

[Schecky]

Looks good. What lens angle?

PS-Here's a battery/charger deal:
http://www.batteryspace.com/index.as...9&SSAID=143703

[92se-r]

I already know about batteryspace, but thanks. Also, I need to run a higher voltage battery on my future LED light because I will be using at least 3 LED's.

[jschwart73]

Have you guys given any thought to running LiPo batteries that started life for RC use? They're significantly more energy dense for the weight, which means you can run a smaller battery that weighs a LOT less. They don't have memory issues and as long as you're careful charging them, they're totally safe.

If you're interested, my RC battery guy is actually looking at the bike light market and probably wouldn't mind talking to a few people and picking their brains a little bit...

[BrewMaster]

Originally Posted by Schecky

Looks good. What lens angle?

PS-Here's a battery/charger deal:
http://www.batteryspace.com/index.as...9&SSAID=143703

That is a great deal. And it would work for my Green Monster...

Nice build. I hope it works well for ya. I don't think the K2s are bad in any way, but I actually prefer working with the star PCB since I am a newb at this. I think the Crees pump slightly more lumens per watt than the K2s, but I could be wrong about that. All I want is light on the trails, everything else is fluff and details.

[Schecky]

Originally Posted by BrewMaster

That is a great deal. And it would work for my Green Monster....

That is what I am going to use it for. A white monster anyway.

[92se-r]

The thing with all LED's is that when junction temperature goes up, light output goes down. With the higher thermal resistance of the CREE's in addition to the STAR, and whatever thermal transfer compound you are using, you probably aren't getting 100% light output unless you do a really good job of removing the heat.

Also, in empirical testing of the K2's with TFFC and the CREE's, I call bullshit on their datasheet. The XRE sample I got was supposed to be around 200 lumens at 700mA. I was driving a K2 with TFFC at 1000mA which is rated at 180 lumens. The K2 definitely looked brighter. You'd be surprised at how easy it was to work with the bare LED K2. The CREE would be a pain in the ass without the STAR PCB. But, I did check out your thread Brewmaster, and you did a really good job with that light. Have you gotten a chance to ride a lot with it yet? I haven't taken mine out yet because it's been raining.

[Bryguy17]

nice light. what optics are those?

in regard to batteries, I'm actually planning on powering my light setup with Lithium polymers. They are a great way to go in terms of energy density, but you do need to be careful with them. If you over charger them, over discharge them, discharge them too fast (hard to do in actuality), charge them too fast, or subject them to anything that would cut the outer layer, well, they like to swell up and potentially explode.

on that note, though, If you have a good place to stash them, they'll be fine. I'll probably make some neoprene wraps that they can fit in.

another thing to keep in mind with the lipos, to get them to last to their full life potential, its better to only discharge 80% of their rated capacity. for example, on a 3000mAh battery, its best to only take 2400mA out of it per discharge.

If you do have any questions about the lipos though, let me know and i can probably answer them. Thats between charger and battery selection to how to charge things right.

Even when you consider all of those things though, I'm still looking at having a ~500 lumen light (dual cree XRE R2) that will run for 2.5 hours and have an all up weight of roughly....250g excellent

that was a stupid long post, but hope its helpful

[92se-r]

I don't buy it that the Cree's put out 250 lumens. Cree's datasheets suck.

[jschwart73]

Originally Posted by Bryguy17

in regard to batteries, I'm actually planning on powering my light setup with Lithium polymers. They are a great way to go in terms of energy density, but you do need to be careful with them. If you over charger them, over discharge them, discharge them too fast (hard to do in actuality), charge them too fast, or subject them to anything that would cut the outer layer, well, they like to swell up and potentially explode.

on that note, though, If you have a good place to stash them, they'll be fine. I'll probably make some neoprene wraps that they can fit in.

another thing to keep in mind with the lipos, to get them to last to their full life potential, its better to only discharge 80% of their rated capacity. for example, on a 3000mAh battery, its best to only take 2400mA out of it per discharge.

If you do have any questions about the lipos though, let me know and i can probably answer them. Thats between charger and battery selection to how to charge things right.

Even when you consider all of those things though, I'm still looking at having a ~500 lumen light (dual cree XRE R2) that will run for 2.5 hours and have an all up weight of roughly....250g excellent

that was a stupid long post, but hope its helpful

Totally agree - The easiest way to make sure you don't over discharge LiPo is to put a voltage cutoff board on to the pack. I also suggest balance charging regularly and when you plan on storing the battery, don't charge to 100% - LiPo batteries actually will go up in voltage as temperature goes up, so you have to give yourself a little room for the voltage increasing.

A majority of LiPo accidents happen with you over discharge a battery, which in reality ends up putting the cells out of match, so that when you charge it with an unbalanced charger, one of the cells is below voltage, so the charger keeps pumping juice to all the cells and the other cells go over voltage, bloat and blow up.

It's kinda fun to do, so my friends tell me..

Handled properly, LiPo is fine - I've seen any number of different NiMh cells explode, so danger with multiple cell packs can happen with any cell type.

[Bryguy17]

iirc the R2's put out roughly 270+/- driven at 1A, so roughly 500 lumens seems reasonable. either way, 2 of any of the latest binned LED's are going to put out a lot of light if they're run at 1A and heatsinked properly. really we just end up arguing the difference of 20-30 lumens over the whole light, which is practically imperceptible to the average person. kind of pointless really.

[BrewMaster]

Originally Posted by 92se-r

But, I did check out your thread Brewmaster, and you did a really good job with that light. Have you gotten a chance to ride a lot with it yet? I haven't taken mine out yet because it's been raining.

I have about 8 or 10 rides under my belt using the Green Monster. It works really well, it just needs narrower lenses. I am happy with it, but I look forward to building a 3x Cree set up whenever I can get my driver.

[92se-r]

My point is, where are you getting these numbers? Cree hasn't put out any datasheets on these R2's. The Q5 that I sampled claimed some pretty good lumens numbers on their datasheets. But they could not compare with the K2's I had. I'm not trying to argue lumens with you. I'm just saying that CREE might overstate their lumens by a lot. The difference between the K2's and the Q5 Cree I had was definitely noticeable.

I'm not trying to say one is better than the other. If I saw some Cree's that were truly brighter than the K2's, then obviously I'd want to buy the Cree's. However, in my experience, that is not the case. I'd really like to see some of these R2's in action.

Originally Posted by Bryguy17

iirc the R2's put out roughly 270+/- driven at 1A, so roughly 500 lumens seems reasonable. either way, 2 of any of the latest binned LED's are going to put out a lot of light if they're run at 1A and heatsinked properly. really we just end up arguing the difference of 20-30 lumens over the whole light, which is practically imperceptible to the average person. kind of pointless really.

[Bryguy17]

fair enough. to be honest, i havn't seen a datasheet on the R2's either, and even if there was one, they dont state the output up to 1A. i remember seeing the 270 lumen number in some CPF forum awhile ago.

more what my point was, was that no matter what LED you go with, you will probably be happy with it. Its really a matter of preference, optic choice, availability, ease of use etc.

but whatever. if you wanna see some Q5 to R2 comparisons theres a thread on mtbr, but i havn't seen very much of anything about the K2s

jschwart, you're completely right about lipo charging. thankfully i fly an rc helicopter so i have all the related stuff to make it work. these things are money for people who dont want to deal with extensive charging setups: http://www.fmadirect.com/detail.htm?...218&section=45

they'll charge practically any lipo that a bike light would need in an hour or less

[jschwart73]

Originally Posted by Bryguy17

fair enough. to be honest, i havn't seen a datasheet on the R2's either, and even if there was one, they dont state the output up to 1A. i remember seeing the 270 lumen number in some CPF forum awhile ago.

more what my point was, was that no matter what LED you go with, you will probably be happy with it. Its really a matter of preference, optic choice, availability, ease of use etc.

but whatever. if you wanna see some Q5 to R2 comparisons theres a thread on mtbr, but i havn't seen very much of anything about the K2s

jschwart, you're completely right about lipo charging. thankfully i fly an rc helicopter so i have all the related stuff to make it work. these things are money for people who dont want to deal with extensive charging setups: http://www.fmadirect.com/detail.htm?...218&section=45

they'll charge practically any lipo that a bike light would need in an hour or less

I'm pretty sure that's the Multiplex charger that everyone and their brother OEM's, good charger for sure.

I have dual Checkpoint chargers now, plus I'm looking at DN LiPo charger to have a cell voltage specific charger - That charger is pretty awesome and not terribly expensive - Check out the OEM'd version that Ballistic batteries sells...

http://www.ballisticbatteries.com/St...589&InfoID=200

What kind of heli do you fly? I've got it bad for a T-Rex 500, but can't bring myself to pull the trigger, since I'm savin' my pennies for an 08 Epic Marathon frameset...

[Bryguy17]

I've only got a trex 450SA, but i blinged out the head with lots of aluminum, so its all good. Unfortunately, its been out of commission for a few months due to lack of funds and decent flying weather.

the only thing thats in my way is sourcing cells or packs that are a low enough discharge rate and at a decent price. Its not like i need the 65 amps worth of discharge i get out of my flightpowers. just need to find some reasonably priced 3200mAh 1C cells