Review: Xtar 3100mAh 18650 protected cell

Detailed and informative .

Thanks for your responses.

If this review format (currently minus discharge curves) provides information that people would find useful, I will happily do some more testing. Future tests should only have the one results table though! And hopefully take half as long.....

Now to get on to the Logview forum and see if I can get some answers re the graphs I want to plot.....

Very nice! You say you paid $26 shipped...is that for a pair or each?

That was for a pair.

Having said that, although I purchased these, they are the same specification as the batteries that have been provided for free for some people to test. In much the same way that Xtar are selling some of the tester spec S1 lights at discount prices, it is possible that I got these cells at a lower cost than the retail spec cells will cost.

Nice review! Thank you for taking your time to do this for us.

Thanks very much Stephen for the careful review! Very well done. I just put one of your pictures at the top for the teaser to make it Frontpage and Sticky.

Thanks - much appreciated.

That is really splendid for a first review!

Nice work and good explanation on why you chose to do it with this format.

I echo the others - great job !

Have someone a link, i didnĀ“t find it, where to buy.

I don't believe that these cells are freely available yet.

They will probably be available from here first, so you may want to keep an eye on that site: -

http://www.szwholesale.com/xtarlight-accessories-battery-c-243_245.html?osCsid=eb2acc3ca265aa747f44fff2be0759a8

No doubt, once cleared for retail sale, they will be available from any Xtar dealer. For that matter, as Xtar have dealt with us before, it's entirely possible that they will become the subject of a group buy in future.

Great review, thanks!

so is this a recommendable cell or not lol?

From what i gathered it is the best one for use with linear regulators (the famous AMC7135 based ones). As the voltage drops goes DD so on a 2,8A driver you get around 2h of decent output (800 down to 400ish lm). Very decent runtimes. There is no real advatage to go below 3V but the 150mAh down o 2.5V are there if really needed.

Excellent review! I would have liked a few hundred mAh more at 3A discharge. Are all the 3100 panasonic equal?

As you can see from the internal resistance table, I have a few other 3100mAh cells to hand, and I intend to test them all, but testing takes a long time. For instance, carrying out a 0.2C discharge test to measure the maximum capacity is always going to take 5 hours, give or take a little, if the capacity is correct. Then over three hours to re-charge at 1A. Obviously, as the stages progress, the higher the discharge rate the shorter the time, but always another three hours to re-charge. Double that for two cells, and you can see how long these tests take! So, don't hold your breath for quick results, but I'll post more tests whenever I can.

Once all the tests are done, we'll be able to see if all the NCR18650A based cells are pretty equal, or if one brand comes out ahead of the others.

With regards to capacity at relatively high current draws, these cells are known for sagging more under load than some other, lower capacity, cells out there.

Did you notice any excessive heat when using them for a high amp LED?

I have noticed something unusual about these cells. I purchased two Citipower X7-T6 from Ebay. If I use a Ultrafire 3000 Mah, the light stays cool but is not extreamly bright. When I switch to the XTAR 18700, the light is 50% (a guess) brighter at the highest setting but the light gets too hot to hold after 20 minutes. I tried switching the batteries to the other light and I can repeat the process.

Does this mean there is a problem with the 18700 or is it just that the LED pulls so many amps that the battery gets hot trying to supply these amps? I have no way to measure the draw of the LED. Could it also just be the lack of a great heatsink on an $18.00 light?

It's hard to say for sure without knowing the exact details of the light, measuring the internal resistance of the batteries, measuring the tail cap current and so on, but if I had to hazard a guess, I would suggest that the light is able to draw more current from the Xtar battery than from the Ultrafire.

Can someone elaborate on L-M-H current draw? I mean, what constitutes a high current draw? I am planning on using these in a 3 cell 3-XML torch. Recommended?

It is generally recommended not to exceed a 2C discharge, unless using cells that you know are rated to be safe with a higher discharge rate.

So, if we were to assume that these cells did have a genuine 3100mAh capacity, and that any loss in capacity I have observed is due to internal resistance in my test equipment, power consumption in the protection circuit, etc. then a 2C discharge would mean that these cells could handle a 6.2A discharge rate.

However, as you can see from the results above, even at 5A, these particular cells were seeing a noticeable degree of reduction in measured capacity, as the voltage was sagging, and hence the voltage dropped down to 3V sooner, and the dicharge was terminated before the cell would actually have been fully discharged.

While these cells may well have been safe to discharge at 6.2A, the capacity would have suffered even more at this high discharge rate.

Some LiCo cells are known not to sag as much as the Panasonic cells under load, and while their capacities may be lower (and hence the 2C discharge rate would be lower), as their voltage remains higher under load, they can run just as long or longer before the voltage drops down to 3V.

The high setting of a light is the only one that should really dictate what cells are suitable, and going back to what I said at the beginning, for most common LiCo cells, you do not want to exceed 2C. If your cells can deal with the high setting of the light, then the medium and low settings should not be an issue. That is assuming of course that the medium and low settings are not likely to risk over discharging the cells (one reason for selecting a light with low voltage warning/cut-out, or using protected cells).

I was interested to see that they discharged at 5A. I asked Xtar what the maximum discharge current was and they told me "<1.5C".

From your photos, I cant see if the pcb has the feint crosshatching like SenyBor 2C batteries, but it looks a similar colour.

The only Senybors I have on hand are a pair of the older, lower drain 2800mAh cells, which have a solid metal base, so can't comment on whether these Xtar cells have the same protection circuits as newer iterations of the Senybor.

I can however confirm that the foil on the base of the protection circuit on the Xtar 3100mAh cells does indeed have a very light crosshatch pattern.