How do I convert a 2D to run on 18650?

[Poppy]

I have this light and would like to run it on an 18650 battery.

I think that I can wrap the 18650, or 26650 with a plastic sleeve to bring it out to the diameter of a D cell.
Make a 55mm long spacer that contains a resistor to make up the difference in voltage between the LiIon, and the 2 alkaline cells.

Is that the cheapest, easiest way to do it?
If so... what size/value resistor should I use?
Thanks!

Summary, better dimming function than any Fenix(so far one of the very few competitors with variable output for <$100) more output than my Lowe's Task Force 2C CREE, but poor build quality

The Brinkmann 3W LED flashlight is the first dimming light I have seen in the mainstream market.
I found mine at a Target store for $25.

Model 809-3000-1

This is an LED flashlight powered by two D cell batteries with 4-level dimming control and a LCD indicator.

In my opinion, the performance is good and beam quality is good. The four dimming levels provides a relative wide range of output with each level providing clearly noticeable dimming.

Operation is very simple. Install two D batteries.

- Use the power button to turn on and off independently of dimming.

- + and - buttons provides dimming control, independent of power switch and the setting sticks after power cycling.

- Test button gives a battery level read-out while the flashlight is turned off. The battery status remains lit whenver the light is turned on.

CREE X-Lamp® 7090 gives this product a technological leap over the many now common Lumileds Luxeon® based products.


The one and only major downer in my opinion is the build quality. This light is supposed to be openable, because the two halves are glued together. Well the gluing sucked on mine. It was no harder to split apart than pulling the foil lid from a cup of yogurt. The plastic has that CHEAP steoreotypical "Made in China" and my gut feel is that if you drop it 3' onto cement, it will shatter and disintegrate.

This flashlight is powered by two D batteries and has a push button operated dimming control with LCD indicator showing current output setting and status of battery. The battery indicator is similar to the indicator on cell phones, with three status bars.

There are 4 buttons:
-on/off
- "+"
- "-"
- Test (used to test status of battery while the light is off)

Buttons have a definite feedback like the buttons on VCR. They do need to be pushed pretty hard and if you use your fingernail, the finish gets scarred. It's purely cosmetic, however.

LED:
CREE X-Lamp® 7090 Star. The star is riveted onto an aluminum heatsink with some thermal compound. There are vent slots cut on both sides of body by the heatsink to help keep the LED cool.

Driver:
Proprietary digitally regulated boost converter. Some competitor products, such as Fenix uses 100% duty cycle variable current drive which can shift the color of LED. This one uses PWM, pulse-width-modulation at ~850 Hz If you swing the light rapidly you can see the flicker, but under normal use it should not be a concern. I should have taken duty cycle measurements at the LED for each setting, but I forgot to do that. Oh well.

Current levels at input with fresh cells in ascending order of dim settings are:
0.1A
0.3A
0.5A
0.85A

Reflector:
Deep, textured plastic reflector with vapor deposited metal reflector.

 

[Chicken Drumstick]

Not really answering your question, but I'd just a 2 or 3 AA to D cell converter and run it on Eneloops. Or if you don't care about runtimes, a 1AA to D cell converter.

 

[Lynx_Arc]

To drop 4.2v down to about 2.8v (estimated) at 0.85A I estimate would require a 1.5-2 Ohm resistor at about 1.5-2 watts and would be wasting over a watt of power in use on high mode assuming the board would draw 0.85A at that rate. If you ebay I would suggest you at least just purchase a cheap 1x18650 battery holder and consider buying a cheap micro usb charging board while you are at it then you can store all of that in the light and open the end cap and either swap out the battery or just plug a micro usb cable in the board and let it charge up. a better thing would be to also replace the driver board for about $4 or so you can either order a cheap board or just buy a cheap 18650 flashlight for the board itself even.

I think the main problem is the switching mechanism itself if you used a new driver then only one button on it would be needed and it wouldn't function the same others trying to use the light would not instantly know how to use it without instruction.

 

[Poppy]

Thanks chickenDrumstick,
Since I already made a spacer so that it would run on the C NiCads, I considered just wrapping a couple of duraloops and using them instead of the Cs. Heck... 2500mah would be the same capacity as the Energizer D NiMH cells, and would be LSD, so they would be better. BUT, my duraloop supply seems to be dwindling, God only knows where they are going. I have more spare 18650s, so I'd like to convert.

I have 7 lights under my workbench, and maybe because of the rubber ends, it is the light I grab more often than any of the others. I had the NiCads because I intended to rebuild a drill battery pack. LOL.. instead I bought a new drill
So that they wouldn't go to waste, I put them in that light.

I have an old NiCad charger that we used when I was a kid, that I keep just to charge those batteries, but I would like to clear my bench a bit, and that charger can go. I just discovered that my Nitecore Intellicharger will also do NiCads.

Lynx_Arc,
Thanks for the suggestion. I think I'll pop on over to an electronics shop and pick up the resistor you suggested. IF he doesn't have that exactly, which direction should I make changes?

Also... the electronics of the light should be able to handle 3 volts... 1.5 + 1.5, is there a resistor that would drop the 4.2 to 3V ?

 

[Chicken Drumstick]

Another solution, although not one solving your issue of spare 18650's....

Might be to try a LiFePo4 18650. I think the MagTac uses these. They are about 3.0-3.2v and might work fine with no other changes needed. You do need a charger to charge these though.

 

[Poppy]

Another solution, although not one solving your issue of spare 18650's....

Might be to try a LiFePo4 18650. I think the MagTac uses these. They are about 3.0-3.2v and might work fine with no other changes needed. You do need a charger to charge these though.

Hey CD,
All smiles... I gotta give you credit for trying :thumbsup:

Once I took the light apart I found that it was a really easy mod; there was plenty or room for the resister, and I didn't have to put it in the battery compartment.

I soldered it between the positive pole connection and the wire that led to the circuit board.

I couldn't get a 2 watt resistor, so I got a 5 watt one.

 

[Lynx_Arc]

Thanks chickenDrumstick,
Since I already made a spacer so that it would run on the C NiCads, I considered just wrapping a couple of duraloops and using them instead of the Cs. Heck... 2500mah would be the same capacity as the Energizer D NiMH cells, and would be LSD, so they would be better. BUT, my duraloop supply seems to be dwindling, God only knows where they are going. I have more spare 18650s, so I'd like to convert.

I have 7 lights under my workbench, and maybe because of the rubber ends, it is the light I grab more often than any of the others. I had the NiCads because I intended to rebuild a drill battery pack. LOL.. instead I bought a new drill
So that they wouldn't go to waste, I put them in that light.

I have an old NiCad charger that we used when I was a kid, that I keep just to charge those batteries, but I would like to clear my bench a bit, and that charger can go. I just discovered that my Nitecore Intellicharger will also do NiCads.

Lynx_Arc,
Thanks for the suggestion. I think I'll pop on over to an electronics shop and pick up the resistor you suggested. IF he doesn't have that exactly, which direction should I make changes?

Also... the electronics of the light should be able to handle 3 volts... 1.5 + 1.5, is there a resistor that would drop the 4.2 to 3V ?

Use a lower value resistor to get higher voltage Ohms law says a 1.2v drop at 0.85 (input) amps is about 1.4 ohms to get power you multiply the voltage drop by amps which gives you 1 watt but if you are going to put it inside where it may not be able to "breathe" properly to shed heat you may want to go up to a higher wattage resistor you could try a 2 ohm and a 4 ohm 1 watt resistor and put them in parallel to get 1.33 ohms at more than 1 watt or a 3 ohm and 2 ohm to get 1.2 ohms and a 1v drop if you think the circuit could handle 3.2v or 3.4v as some D alkalines do come at 1.6v

P.S. Nicads suck IMO unless you want to leave something on a charger or use it weekly I've always had them dead on me when I really need them. I have 2 9.6v drills that can use the same battery and both batteries for them no longer stay charged long enough to last a few weeks without charging. I'm trying to get some tabbed 2500mah high current 18650s to mod a battery powered (nicad) soldering iron because it won't stay charged longer than 2 months and I need to use it once every 4-6 months and it takes an hour to charge by the time it is charged I've already got a corded iron out and done the job.

 

[Poppy]

Use a lower value resistor to get higher voltage Ohms law says a 1.2v drop at 0.85 (input) amps is about 1.4 ohms to get power you multiply the voltage drop by amps which gives you 1 watt but if you are going to put it inside where it may not be able to "breathe" properly to shed heat you may want to go up to a higher wattage resistor.
You could try a 2 ohm and a 4 ohm 1 watt resistor and put them in parallel to get 1.33 ohms at more than 1 watt,
or a 3 ohm and 2 ohm to get 1.2 ohms and a 1v drop if you think the circuit could handle 3.2v or 3.4v as some D alkalines do come at 1.6v

P.S. Nicads suck IMO unless you want to leave something on a charger or use it weekly I've always had them dead on me when I really need them. I have 2 9.6v drills that can use the same battery and both batteries for them no longer stay charged long enough to last a few weeks without charging. I'm trying to get some tabbed 2500mah high current 18650s to mod a battery powered (nicad) soldering iron because it won't stay charged longer than 2 months and I need to use it once every 4-6 months and it takes an hour to charge by the time it is charged I've already got a corded iron out and done the job.

Lynx_Arc,
Thank you so much :thumbsup:

With a fully charged 18650, the light is working as it should. The dimmer is working, and the battery state of charge indicator is at full charge. I don't know if it will indicate when the battery is depleted. Time will tell, but in the meantime, I put a protected cell in there.

At any rate... thanks to your help, I am very pleased with myself!

I kept a NiCad drill 2 years longer than I should have because I thought that a 12V battery had more uses, than the 18V LiIon batteries that most newer drills run. (In a pinch, I had used the 12V battery to power a small boom-box radio during a power outage.)

 

[DIWdiver]

At the lowest setting, the voltage drop across the resistor will be almost negligible. If the light works okay at the lowest setting, you probably don't need the resistor at all.

I wouldn't have thought that would work, and would have advised against it. Good thing I'm a bit late to the party!

 

[Poppy]

Yes, it seems that all four levels are working just fine.

 

[Lynx_Arc]

Lynx_Arc,
Thank you so much :thumbsup:

With a fully charged 18650, the light is working as it should. The dimmer is working, and the battery state of charge indicator is at full charge. I don't know if it will indicate when the battery is depleted. Time will tell, but in the meantime, I put a protected cell in there.

At any rate... thanks to your help, I am very pleased with myself!

I kept a NiCad drill 2 years longer than I should have because I thought that a 12V battery had more uses, than the 18V LiIon batteries that most newer drills run. (In a pinch, I had used the 12V battery to power a small boom-box radio during a power outage.)

I doubt the battery indicator will work right you will have to measure the voltage of it when it drops levels to get an idea. The protection circuit may act as a resistor also dropping the output some depending on which resistance combination you chose.