Led Lenser X21 with 18650??

Hi there,

I have a Led Lenser X21 and I really want to be able to use 18650s instead of the 4D's... Im not an expert on electronics at all so I don't even know if it is possible but I really don't want to have all different sized batteries and chargers for my different flashlights. Let me know what i'd have to do...

Unfortunately, using an 18650 in the x21 would be very difficult. You can just enjoy the lights you have and make a plan to standardize with future purchases.

run nimh d cells, not recommended by lenser but wayyyy more punch (for 5 mins lol) gotta love direct drive. 18650s in a reducer would instaflash an expensive light dont do it

Mukiwa19 said:

Hi there,

I have a Led Lenser X21 and I really want to be able to use 18650s instead of the 4D's... Im not an expert on electronics at all so I don't even know if it is possible but I really don't want to have all different sized batteries and chargers for my different flashlights. Let me know what i'd have to do...

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Four D cell alkaline batteries produce 1.5 volts each for a total of 6 volts driving the X21 led's
18650 batteries each produce nominal voltage of 3.7 volts, so the maximum number of cells you can wire in series without torching your light is 2.

You've got a couple of options:
1. Sell the light
2. Purchase some eneloop NiMh cells and the D cell adapters.
3. Purchase a couple of 26650 batteries, and fabricate a battery carrier to wire them in series.
4. Fabricate a battery carrier for installing two 18650 batteries.

You've got a couple of options:
1. Sell the light
2. Purchase some eneloop NiMh cells and the D cell adapters.
3. Purchase a couple of 26650 batteries, and fabricate a battery carrier to wire them in series.
4. Fabricate a battery carrier for installing two 18650 batteries.

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1. I will probably end up selling it but I love the zoom function as it makes it 1000lms of super flood or super throw within a second.
2. Are D cell adapters just a bunch of aa cells that fit a D? or does eneloop sell a D size?
3/4. Could someone with the right expertise wire 4 cells together with two sets in parallel with each other? How big are 18650 vs D? how many could you fit into a light made for 4 D cells?

thanks for your help!

I don't think two Li-Ion batteries in series is a good idea for this light. Four alkaline batteries will put out around 6.0V when new. But two Li-Ion batteries will produce 8.4V freshly charged, and about 7.4V nominally under a load. Without knowing anything about the circuitry used in this light, it is quite possible that this higher voltage could damage the light. I would instead consider doing a couple of other things. First of all, try one Li-Ion battery. This may seem like it wouldn't produce sufficient voltage. But keep in mind that the voltage of four alkaline batteries is going to drop DRASTICALLY under the load of the light. A single Li-Ion 18650 or 26650 will sag MUCH less under a load than alkalines. So the lower open circuit voltage will be less of an issue. The other option is to use NiMH. Rather than getting those silly AA adaptors, get REAL D cells, such as Tenergy Premiums or Centuras. This is probably your best option for this light.

i use nuon brand junk nimh d cells from batteries plus and they work great

pparmenter said:

i use nuon brand junk nimh d cells from batteries plus and they work great

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Are these rechargable? I want to be able to recharge them as it goes thru them fairly quick.

As mentioned by Matt,i would go with the tenergy D cells, LSD and 10,000mah

ven said:

As mentioned by Matt,i would go with the tenergy D cells, LSD and 10,000mah

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Not quite. The LSD cells are actually only 8000mAH, but that's certainly respectable in and of itself. The 10000mAH cells are the Tenergy Premiums. These are not LSD. But they actually do a pretty respectable job of holding a charge. They will certainly hold a decent charge for at least a couple of months.

PM sent with link of tenergy 10,000mah low self discharge advertised.

ven said:

PM sent with link of tenergy 10,000mah low self discharge advertised.

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That's downright odd that Tenergy is now selling their Premium cells as LSD. Because if they are, why would they need to sell the lower capacity LSD Centuras. Admittedly, the Premiums actually DO have a fairly low self discharge rate. But I would call them more medium self discharge that low self discharge.

As StorminMatt stated earlier, buy some good NIMH D cells. I use Powerex and Tenergy cells that are rated at 10,000 and 11,000 mah. I have also used Radio Shacks D cells. They are a lot cheaper, around $15.00 for a pair, but are just 5000 mAh. They are still a lot better than the fake Energizer ones. The D NIMH cells will give you much better runtime than any 18650 and they are safer.

mikekoz said:

The D NIMH cells will give you much better runtime than any 18650 and they are safer.

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And they are actually what the light is built to take. Why try to reinvent the wheel, only to end up with something that ultimately won't work as well?

ven said:

PM sent with link of tenergy 10,000mah low self discharge advertised.

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For some reason I can't find the pm? My inbox is empty... I was looking on Amazon and found 8 Tenergy D batteries for $56... Is that expensive? I don't really know what they usualy go for...

StorminMatt said:

And they are actually what the light is built to take. Why try to reinvent the wheel, only to end up with something that ultimately won't work as well?

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That does make sense... As you can probably tell I am a real newb and am learning about this stuff as fast as I can. I wanted to standardize all my batterys but I found an adapter that I can use to charge D cells in a regular charger.. I'm looking at the XSTAR VP4 charger right now which should fit the D's using the AA adapter...

how about lifepo4?

LiFePO4 could work if you replace two alkaline batteries with one LiFePO4 (preferably a 32600/32650 in this case). But even this might be too 'hot'. Two LiFePO4 are going to give 7.2V fresh off the charger, which could be too much. And even if you draw them down to plateau before putting them in the light, you will still have 6.4 rather stable volts, which may be too much.

Mukiwa19 said:

For some reason I can't find the pm? My inbox is empty... I was looking on Amazon and found 8 Tenergy D batteries for $56... Is that expensive? I don't really know what they usualy go for...

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I just sent matt the link with the tenergy description mentioning LSD ,it's on their site but not allowed to post links on here.