how to use a Cree LED with a 18650 element

[Florin Andrei]

I have several 18650 flashlights, batteries, and a charger. They work just great.

I'm making a tree house for my kids, I'm almost finished. We need some kind of light source inside, and I thought I could use a single 18650 element for light and for a couple 5V fans to blow some cool air inside. Perhaps use a Cree LED with the 18650, e.g. like this one:

http://www.ledsupply.com/creexpg2-ww121.php

When the battery runs out of juice, the kids could run inside the house and swap it for a charged one.

The thing is, I don't know much about these LEDs. Are there any drivers I could buy, that would allow me to use a Cree LED with a single 18650 cell? I'm guessing the answer is yes, since there are flashlights out there that use a Cree LED and a single 18650 element.

Alternatively, I could build a constant current driver myself (I did a lot of electronics design in the past), and just feed the LED something like 350 mA. The voltage budget is pretty tight, since the voltage drop on the LED is pretty close to the voltage on the 18650, but I think I could pull this one off.

But I'd very much prefer to buy a driver instead of building one from scratch.

As a last resort, I could disassemble a flashlight and convert it into a flood light, or lantern, or ceiling light. But I'd rather not do that.

Any ideas, suggestions?

Thanks.

 

[Thr3Evo]

First off, I commend you for being a good dad :)

Now to your question. Since you are budget oriented, I would suggest the Amc7135 boards. Depending on what emitter(s) you chose and how much light you require will dictate the amount of chips on your board you should buy(each "new" 7135 chip gives 380mA, the older ones were 350mA).
If you are willing to swap time for some savings, head on over to FastTech dot Com and browse their site. Great prices on cells, emitters and drivers for budget oriented folks. You can find really great deals on the XML (the previous ones and the new version) there as well, which I recommend for the extra buck or two since they are more efficient and at lower currents will run cooler.

DON'T FORGET that unprotected 18650's can be ruined if drained pased 2.5V. I don't even let mine get pased 3.5V
And one more very important issue(this is dependant on power used), HEATSINKS
BTW ... you Romo?

 

[Florin Andrei]

Thanks for your suggestions!

I ended up ordering a Cree XM-L2 T6-1C 10W 6500K emitter and a 10-pack of AMC7135 380mA driver chips on Fast Tech.

http://www.fasttech.com/product/1277804

http://www.fasttech.com/product/1197600

It was difficult to choose between all those different types of emitters, especially given that Fast Tech does not provide much tech data for their products. Fortunately, ledsupply.com has original PDF sheets for their products, so I was able to choose the XM-L2 based on the good flux performance and the low forward voltage (which is a requirement with a simple driver like this, when using a single cell).

Those driver chips are very inexpensive. If I need more light, I can always connect two in parallel - given that they are constant current generators, it's ok to connect them in parallel on the same LED (with a common plus wire).

 

[Julian Holtz]

Hi!

You might want to consider an LED with less than 4500k color temperature, te make the treehouse the cosy place it is intended to be.

Also, I would recommend a switching driver, like this:

http://www.ebay.de/itm/DC-Adjustabl...268?pt=LH_DefaultDomain_0&hash=item5aef7d4654

You can adjust the current, and it will run for months when hooked to an old car or motorcycle battery.

 

[SemiMan]

I have several 18650 flashlights, batteries, and a charger. They work just great.

I'm making a tree house for my kids, I'm almost finished. We need some kind of light source inside, and I thought I could use a single 18650 element for light and for a couple 5V fans to blow some cool air inside. Perhaps use a Cree LED with the 18650, e.g. like this one:

http://www.ledsupply.com/creexpg2-ww121.php

When the battery runs out of juice, the kids could run inside the house and swap it for a charged one.

The thing is, I don't know much about these LEDs. Are there any drivers I could buy, that would allow me to use a Cree LED with a single 18650 cell? I'm guessing the answer is yes, since there are flashlights out there that use a Cree LED and a single 18650 element.

Alternatively, I could build a constant current driver myself (I did a lot of electronics design in the past), and just feed the LED something like 350 mA. The voltage budget is pretty tight, since the voltage drop on the LED is pretty close to the voltage on the 18650, but I think I could pull this one off.

But I'd very much prefer to buy a driver instead of building one from scratch.

As a last resort, I could disassemble a flashlight and convert it into a flood light, or lantern, or ceiling light. But I'd rather not do that.

Any ideas, suggestions?

Thanks.

If you could mount a solar panel somewhere that is gets a reasonable amount of sun for part of the day, that may be a better option. A 12V, 10AH lead acid battery is pretty cheap and you could run 3-watts of LEDs for 30 hours before running the battery out. More realistically it will get used a few hours a night, and likely not every night. A 5 or 10 watt panel could be more than enough to keep the battery topped up.

A simple hanging flashlight may be the easiest thing to do, but something in solar would be fun and educational for the kids.

Semiman

 

[Bolek]

When the battery runs out of juice, the kids could run inside the house and swap it for a charged one.


Any ideas, suggestions?

Thanks.

My suggestion : do not alow your kids play with a 18650. 18650 swap is for dady only.

 

[waehrik]

If you could mount a solar panel somewhere that is gets a reasonable amount of sun for part of the day, that may be a better option. A 12V, 10AH lead acid battery is pretty cheap and you could run 3-watts of LEDs for 30 hours before running the battery out. More realistically it will get used a few hours a night, and likely not every night. A 5 or 10 watt panel could be more than enough to keep the battery topped up.

A simple hanging flashlight may be the easiest thing to do, but something in solar would be fun and educational for the kids.

Semiman

I completely agree with the solar idea. I tend to keep batteries that are no longer good enough for their original applications but can be repurposed for other uses. I have several motorcycle and garden tractor batteries that have been used for portable power (running a drill off an AC inverter in a scrap yard) and could also be used for the solar project. If you don't have a battery on hand, try your local garage, some might be willing to give you an old battery that wouldn't work in a car but would be more than enough to power a flashlight. Or if you end up buying something, get a deep cycle so it won't be ruined when the kids inevitably leave the lights on.