# Test/Review of Keeppower 16650 2000mAh (Black)



## HKJ (Aug 18, 2012)

[size=+3]Keeppower 16650 2000mAh (Black)[/size]







Official specifications:

16650 2000mAh Protected Rechargeable Battery
Min Capacity: 2000mAh
Typical Capacity: 2100mAh
Normal Voltage: 3.7V
Quality Lithium Ion rechargeable cell
In Built Safety Circuitry
Protection Circuit (Against overcharge, over discharge, over current and short-circuit.)
4.3 volts max voltage and 3.6-3.7 volts nominal voltage






This battery is a 16650, i.e. it the diameter is less than 18650 batteries, this makes it a good battery for 2xCR123 substitution in lights that are to tight for a 18650.
To get the full capacity from the battery it must be charged with a 4.3 volt charger.


























The protection PCB restrict the current to somewhere between 2 and 3A continuous load.





















The protection PCB stops this test premature.






The batteries can hand about 3.3A for a short time.








[size=+3]Test with 4.2 volt charging[/size]






When charged on a 4.2 volt charger, there is about 80mAh capacity loss.






































[size=+3]Conclusion[/size]

The battery size is interesting and can be useful and because it is a new generation LiIon it has better capacity than 17670 batteries, even when only charged to 4.2 volt. As long as it is used to replace CR123 batteries, the current limit will seldom be a problem.
All in all I will rate it as a good battery.



[size=+3]Notes and links[/size]

Keeppower is a OEM manufacturer, i.e. many of the batteries they produce is sold with other names on them.

The batteries was supplied by Keeppower for review.

How is the test done and how to read the charts
How is a protected LiIon battery constructed
More about button top and flat top batteries


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## MichaelW (Aug 23, 2012)

Do these use the LiNiCoO2 NNP cell design?
Will the 17670 ever increase in capacity?


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## HKJ (Aug 23, 2012)

MichaelW said:


> Do these use the LiNiCoO2 NNP cell design?



That is a Panasonic technology and this cell was designed by Sanyo (Sanyo is now a part of Panasonic). The Sanyo datasheet does not specify anything about cell design.



MichaelW said:


> Will the 17670 ever increase in capacity?



Depends, if some manufacturer want to use a few millions cells in that size, the large LiIon manufacturer might update the design.


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## BenChiew (Jun 8, 2013)

Any news updates on this battery? Perhaps from someone that has used it. 
Any issues with usage and charging?


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## välineurheilija (Jul 12, 2013)

Benchiew said:


> Any news updates on this battery? Perhaps from someone that has used it.
> Any issues with usage and charging?


I am using this battery in a Surefire G2X pro but i havent done any runtime tests and i charge it with a Nitecore intellicharger I4 V2.No problems so far


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## LEDAdd1ct (Jul 12, 2013)

HKJ, what say you?

How is this cell holding up?


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## HKJ (Jul 12, 2013)

LEDAdd1ct said:


> HKJ, what say you?
> 
> How is this cell holding up?



Being a Sanyo cell, I would not expect any problems with lifetime, but I have no data on it.


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## LEDAdd1ct (Jul 13, 2013)

Roger that.

Thank you.

Now that Sanyo is a (subsidiary?) of Panasonic, what will happen to Sanyo branded cells?


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## Diesel Pro (Jan 10, 2014)

I have a couple of lights that could use these batteries, but I have a couple of questions:

1) How much capacity is lost at 4.3v versus 4.3v?

2) Why 4.3 when 4.2 seems to be the standard?

3) Will a typical protected cell by other mfr charge safely in a charger that outputs 4.3v?

4) Is there a good charger that can do multiple different batteries and 4.3v that you'd recommend? I'm thinking 26650, 18650, maybe 17670, and possibly some aa type shorts.

The Thrunite MCC-4 looks decent, but is 4.2v and a USB out would be handy.


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## HKJ (Jan 10, 2014)

Diesel Pro said:


> I have a couple of lights that could use these batteries, but I have a couple of questions:
> 
> 1) How much capacity is lost at 4.2v versus 4.3v?



Please check the review, it contains data for both 4.3 volt and 4.2 volt.



Diesel Pro said:


> 2) Why 4.3 when 4.2 seems to be the standard?



This is one way to increase capacity.



Diesel Pro said:


> 3) Will a typical protected cell by other mfr charge safely in a charger that outputs 4.3v?



Mostly, especially with cheap batteries there is an increased risk (The big brands are tested that they can handle over charge).
Using 4.3 volt on a 4.2 volt battery will overcharge the battery and seriously reduce lifetime.



Diesel Pro said:


> 4) Is there a good charger that can do multiple different batteries and 4.3v that you'd recommend? I'm thinking 26650, 18650, maybe 17670, and possibly some aa type shorts.



It looks like Xtar has a new charger that can do 4.35 volt, but I have not tested it yet.
At the current time the best solution for 4.30 volt is a hobby charger, where the output can be adjusted (Like iCharger), but that adjustment can only be adjusted to 4.30 volt, not 4.35 volt (As some other batteries requires).



Diesel Pro said:


> The Thrunite MCC-4 looks decent, but is 4.2v and a USB out would be handy.



The usb output on chargers can usual not be used while it is connected to power, only from a battery and for that purpose I will recommend getting a separate usb box.


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## tobrien (Jan 10, 2014)

HKJ, I have two of these cells and just to clarify, is 4.*35* volts what the charger will have to put out?

I am going to be buying an XTAR SP1 for some LG D1 cells (I will be buying those D1 cells at the same time as the SP1), but it appears there are 4.*3* volt cells as a different class or something.

Are 4.35 and 4.3 volt cells the same thing or is it just semantics that is causing this confusion? 

This review says 4.3 volts, but cottonpicker's charger and the XTAR SP1 both say 4.3*5* volts, for example, so is this cell not okay to use with the cottonpickers 4.35v charger or the XTAR SP1?

edit: my two 16650 2000 mAh cells I actually bought because of your review! 

I see you kind of answered this question in the post above, but I'm not entirely clear still on if 4.3 vs. 4.35 is a huge difference or just a semantics thing or they shouldn't be mixed lol


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## HKJ (Jan 10, 2014)

tobrien said:


> HKJ, I have two of these cells and just to clarify, is 4.*35* volts what the charger will have to put out?
> 
> I am going to be buying an XTAR SP1 for some LG D1 cells (I will be buying those D1 cells at the same time as the SP1), but it appears there are 4.*3* volt cells as a different class or something.
> 
> ...



There are both 4.30 and 4.35 volt cells, they are not the same thing.

Using a 4.35 volt charger on a 4.30 volt will overcharge it and reduce the lifetime of the cell.


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## msnake103 (Aug 3, 2014)

I looked at these batteries for a while before placing them in two slightly modified Surefire E2D models. The first is an incandescent with a Lumens Factory EO-E1R 3.6V bulb, and the second is a LED with a Malkoff Devices E2/Scout M600 2-3 CR123 3.4-9.0V head. While I don't have the equipment or experience to provide any detailed runtimes or battery performance data, I can say that the batteries fit perfectly in a E2 body and have performed very well in both lights while carried on a rotating daily basis.


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## editedby (Sep 23, 2014)

I'm not able to locate these from a USA dealer. Anyone have a source? FYI Keeppower.com.cn has these listed as 2200 @3.7


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## __philippe (Sep 23, 2014)

Try here:

http://www.doingoutdoor.com/2pcs-keeppower-16650-battery-lithium-ion-protected-p-711.html

__philippe


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## pilou (Oct 2, 2014)

__philippe said:


> Try here:
> 
> http://www.doingoutdoor.com/2pcs-keeppower-16650-battery-lithium-ion-protected-p-711.html
> 
> __philippe




That's not a USA dealer. It's based in China.


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## __philippe (Oct 3, 2014)

If you ask me, CN dealer trumps no dealer at all. Beggars can't be choosers...

__philippe


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## BillSWPA (Nov 5, 2014)

Just ordered two of these from Illumination Supply, although they are 2,500 mAh instead of 2,000 mAh, with a maximum voltage of 4.35 v. If these work as expected in my FourSevens QT2L, I may be looking for a 4.35 v. charger. If the unused capacity from using a 4.2 v. charger is on the same order as the 2,000 mAh cells tested above, it does not appear that I will be losing much capability by using my current 4.2 v. charger until a 4.35 v. charger can be located.


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## Aperture (Nov 9, 2014)

I have two of these 2000mAh batteries and they fit perfectly in stock Surefire E2E, 6P and C2 bodies.

It's mainly used charged to 4.2V with Tana's low voltage TripLED 219 on an 11 year old E2O body with the option to switch to AA in case they run out.


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## tobrien (Nov 13, 2014)

BillSWPA said:


> Just ordered two of these from Illumination Supply, although they are 2,500 mAh instead of 2,000 mAh, with a maximum voltage of 4.35 v. If these work as expected in my FourSevens QT2L, I may be looking for a 4.35 v. charger. If the unused capacity from using a 4.2 v. charger is on the same order as the 2,000 mAh cells tested above, it does not appear that I will be losing much capability by using my current 4.2 v. charger until a 4.35 v. charger can be located.


I think the difference with the new Keeppowers is they are UR16650_ZT*A*_, whereas what HKJ reviewed here were the UR16650_ZT_ (no -A at the end)


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## scout24 (Dec 6, 2014)

Just ordered a pair of the "A" suffix 2500ma protected cells from doingoutdoor via Amazon. Looking forward to seeing how they work on a 4.2v charger, and how quick shipping is. More capacity than 17670's, and I won't use these in the high-drain stuff.


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## LightWalker (Dec 31, 2014)

Are these actually shorter than the AW 17670?


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## Bright_Light (Dec 31, 2014)

I have the new KeepPower 16650 2500mAh UR16650ZTA 4.35V battery and it fits a LITTLE tighter in my WF-139 charger. So just a hair longer than AW 17670.


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## LightWalker (Jan 1, 2015)

Bright_Light said:


> I have the new KeepPower 16650 2500mAh UR16650ZTA 4.35V battery and it fits a LITTLE tighter in my WF-139 charger. So just a hair longer than AW 17670.



Ok, thank you.


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## CSSA (Jan 12, 2015)

Orbtronic (orbtronic.com) expects to have 16650 protected cells available next week. 
What charger would you recommend to charge the 16650? XTAR says the VP2's 3.8 Volt setting charges to 4.35V.
"Output: DC 3.0/4.35v
3.0v/3.2v LiFePO4 Battery Charger (Charges to 3.2v)
3.6v/3.7v Li-ion Battery Charger (Charges to 4.2v)
3.8v Li-ion Battery Charger (Charges to 4.35v)" _XTAR VP2 Specs_


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## Bright_Light (Jan 12, 2015)

Just an FYI,

I got my new Xtar WP2H charger in today and I can't get my KeepPower 16650 2500mAh UR16650ZTA battery to charge up to 4.35V. The charger gives me the "short circuit" warning and stops charging the batteries at 4.17V when using the 1 amp setting. I can get it to charge up to 4.21V when I use the .25 amp setting before the charger gives me the "short circuit" warning.

So it must have something to do with KeepPower's protection circuit. That's my guess at least....


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## thedoc007 (Jan 12, 2015)

Bright_Light said:


> Just an FYI,
> 
> I got my new Xtar WP2H charger in today and I can't get my KeepPower 16650 2500mAh UR16650ZTA battery to charge up to 4.35V. The charger gives me the "short circuit" warning and stops charging the batteries at 4.17V when using the 1 amp setting. I can get it to charge up to 4.21V when I use the .25 amp setting before the charger gives me the "short circuit" warning.
> 
> So it must have something to do with KeepPower's protection circuit. That's my guess at least....



Interesting, I have a VP2, and the same Keeppower 16650. Testing now - it has been a while since I needed to charge (run it in my Elzetta, and 235 lumens takes a LONG time to drain a 2500 mAh cell). Perhaps the protection circuit was not properly designed for the higher voltage? We shall see...


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## Bright_Light (Jan 12, 2015)

thedoc007 said:


> Perhaps the protection circuit was not properly designed for the higher voltage? We shall see...



Maybe.

Let us know what happens with your test. Thanks


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## thedoc007 (Jan 12, 2015)

At 4.26 volts, as indicated by digital readout on my VP2. No issues so far, still charging away.


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## thedoc007 (Jan 13, 2015)

Bright_Light said:


> Just an FYI,
> 
> I got my new Xtar WP2H charger in today and I can't get my KeepPower 16650 2500mAh UR16650ZTA battery to charge up to 4.35V. The charger gives me the "short circuit" warning and stops charging the batteries at 4.17V when using the 1 amp setting. I can get it to charge up to 4.21V when I use the .25 amp setting before the charger gives me the "short circuit" warning.
> 
> So it must have something to do with KeepPower's protection circuit. That's my guess at least....



Well, it isn't just your cell. It seemed to be running OK, but of course the readout leads the actual voltage by a bit (more at higher charge rates). My cell stops a bit shy of 4.2 volts also. 

I just noticed that the label on the cell lists it as 3.7 volts. If the spec was correct, full charge at 4.35 volts, it should be listed as a 3.8 volt cell. So now I am really annoyed. Whether or not the original cell was rated for 4.35 volts, I'm not sure, but clearly the protection circuit is not going to allow a 4.35 volt charge. So the specs (I bought mine at Illumination Supply) were definitely misleading. I wish I had a way to measure the total capacity of the cell, with a 4.2 volt charge. I suspect it will be substantially lower than 2500mAh.

Overall, I still think it is a good cell. As I said before, I get plenty of runtime. But I will be informing Keeppower and Illumination Supply about the charging issue, and hopefully they will get the specs updated.


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## Bright_Light (Jan 13, 2015)

Thanks for your report, thedoc.

I bought mine from Illumination Supply as well. Let us know if you hear anything back from Illumination supply or Keeppower. 

Thanks again


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## Aperture (Jan 13, 2015)

thedoc007 said:


> I suspect it will be substantially lower than 2500mAh.


The 2000mAh version tested by HKJ only looses 72mAh when charged at 4.2V, nothing to worry about IMO.


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## thedoc007 (Jan 19, 2015)

Bright_Light said:


> Thanks for your report, thedoc.
> 
> I bought mine from Illumination Supply as well. Let us know if you hear anything back from Illumination supply or Keeppower.
> 
> Thanks again



I did hear back from Illumination Supply. They have updated the listing with a note about the protection circuit - it was simply an error of omission. Apparently all of the KP protected 16650s have the same 4.2V cutoff.


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## Bright_Light (Jan 19, 2015)

Thanks for reporting back. Hopefully Keeppower will use a 4.35V cutoff protection circuit some time in the future. I really like these 16650s with my Surefire G2L hosts.


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## Greenbean (Jan 22, 2015)

I have two off these coming from Amazon, hoping to use in a G2 and a Quark 123x2 Turbo.


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## HistoryChannel (Jan 27, 2015)

So what would be best to run SF123a Surefire Lights that won't take the 18650 cells? 

The KeepPower 16650 2500mah battery or 2 x K2 LiFePO4 600mah batteries? I'm thinking it's better to run the KeepPower 16650? Why would Surefire pick such a low performer to sell (LFP123a) if a 16650 Sanyo/Panasonic cell would work better?


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## thedoc007 (Jan 27, 2015)

HistoryChannel said:


> So what would be best to run SF123a Surefire Lights that won't take the 18650 cells?
> 
> The KeepPower 16650 2500mah battery or 2 x K2 LiFePO4 600mah batteries? I'm thinking it's better to run the KeepPower 16650? Why would Surefire pick such a low performer to sell (LFP123a) if a 16650 Sanyo/Panasonic cell would work better?



Definitely, unquestionably, the Keeppower 16650. Single cell is safer, and you will get a lot more runtime. 

Surefire is quite often behind the curve...their first light that takes 18650 was only released a few months ago.


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## Timothybil (Jan 27, 2015)

The other thing to remember is that until very recently, all Surefire lights (except the ones that used the B65 rechargeable battery) were designed for primary cells only. People have been wanting to use rechargeable cells since the first RCR and 16340 cells came out, but the voltage mismatch was too great for their incandescent lamp assemblies. Their answer was the LiFePO4 cells because their voltage is almost a perfect match for a CR123 primary. With the conversion to LEDs, some started using LiIon cells with sometimes mixed results. Now that they are finally doing mixed fuel and 18650 lights, things should work better.


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## HistoryChannel (Jan 27, 2015)

I have a couple of 16650 KeepPowers coming this Fri so I can try them out. Surefire is kind of like Apple, I guess they don't want to be first to the market necessarily because that creates all kinds of problems with reliability and end user experience problems, etc. That being said, I suppose Surefire isn't in the battery business so it's probably just not a priority for them?

Good point also about the lights were designed to be used with SF123a Lithium batteries, and since demand for a rechargeable option is so high (me assuming) that they put a band-aid on the demand by selecting the K2 LFP123a as their "Officialy" endorsed rechargeable option for their non-rechargeable lights. 

It's a good sign with the release of the P1R and hopeful release of the R2 Lawman that more 18650 Li-Ion flashlights are on the way... Although, it wouldn't be a big deal for SF to just bore out the Fury series to 18650 size and offer both options? Instead they decided to create a whole new light (P1R) and bundle it with their own charger and battery. I've been wanting to buy another P1R but I already have a gazillion 18650 batteries and chargers that I can't justify buying another package set. 

Thanks for the responses, I definitely look forward to trying out the 16650.


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## HistoryChannel (Jan 30, 2015)

Ok, I got the KeepPower 16650 2500ma batteries and like others have experienced.... Even on the 3.7v (4.35 cutoff) setting on the Xtar VP2, it appears that the on board circuit of the battery cuts off the charging at around 4.29 v. 

It's a tight fit but it fits in the G2X Pro and E2B and I can't perceive any brightness loss initially. 

Thanks for the great review that made me try these.


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## chazz (Jan 31, 2015)

HistoryChannel said:


> Even on the 3.7v (4.35 cutoff) setting on the Xtar VP2, it appears that the on board circuit of the battery cuts off the charging at around 4.29 v.



I could be wrong, but I think the newer 2500 mAH versions are only supposed to be charged to 4.2V 

Or maybe the internal cell is 4.35V Capable but the protection circuit is not. 

I wonder if the Orbtronic versions will allow the higher voltage if/when they show up. (IF they use the same base cell)


Sent from my iPhone using Candlepowerforums


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## thedoc007 (Jan 31, 2015)

chazz said:


> Or maybe the internal cell is 4.35V Capable but the protection circuit is not.



This is the correct answer. I talked to Illumination Supply about it...the base cell is definitely rated for 4.35 volts, but the protection is set lower, it does not allow a full charge. The listing has been updated to reflect that fact, at least at IS.


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## RI Chevy (Jan 31, 2015)

Has anyone stripped the protection circuit and rewrapped the cell yet?


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## thedoc007 (Jan 31, 2015)

RI Chevy said:


> Has anyone stripped the protection circuit and rewrapped the cell yet?



I don't see a reason to do it, even if I knew how to do it safely. The capacity difference is relatively small, the longer cell fits better (two CR123s are 68 millimeters), and you lose the protection. Not worth it, to me at least.


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## LightWalker (Jan 31, 2015)

RI Chevy said:


> Has anyone stripped the protection circuit and rewrapped the cell yet?



They have them without the protection circuit, I'm charging one now.


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## recDNA (Jan 31, 2015)

LightWalker said:


> They have them without the protection circuit, I'm charging one now.


That will be interesting. I assume it is narrower too. The 16650 is wider than some of my protected 17670.


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## LightWalker (Jan 31, 2015)

recDNA said:


> That will be interesting. I assume it is narrower too. The 16650 is wider than some of my protected 17670.



The unprotected 16650 is narrower than the protected AW 17670.


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## recDNA (Jan 31, 2015)

No I mean is the unprotected kp 16650 narrower than the protected kp 16650. The 17670 I have that is narrower than the protected 16650 is a blue safefire protected 17670. It is narrower than the aw or the kp.


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## LightWalker (Jan 31, 2015)

Oh, ok, I don't have a protected one yet so I can't say.


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## Raphion (Feb 1, 2015)

I got the 2500mAh flavor of this one for my Quark QT2L-Xs with burst, and I'm very impressed. I'm getting run-time that meets or exceeds using 2xCR123a primaries! Prior to this, I'd been using Chinese Tenergy brand RCR123a that didn't even get half the run-time of primaries, and would more often than not balk at current demand of burst mode and shut down. No problems at all with the Keeppower 16650s.

I'm charging them with the Efest LUC v4, most likely the newer revision that stops at 4.2 volts.


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## LightWalker (Feb 12, 2015)

Protected buttontop next to unprotected flattop.


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## Ben850 (Apr 14, 2015)

Raphion said:


> I got the 2500mAh flavor of this one for my Quark QT2L-Xs with burst, and I'm very impressed. I'm getting run-time that meets or exceeds using 2xCR123a primaries! Prior to this, I'd been using Chinese Tenergy brand RCR123a that didn't even get half the run-time of primaries, and would more often than not balk at current demand of burst mode and shut down. No problems at all with the Keeppower 16650s.
> 
> I'm charging them with the Efest LUC v4, most likely the newer revision that stops at 4.2 volts.



Thanks for the info! Hows the fit? Does this 16650 just drop in, or does it need some persuasion?

i am really excited to have a single-cell solution for my QT2L-X


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## UnderPar (Apr 14, 2015)

Ben850 said:


> Thanks for the info! Hows the fit? Does this 16650 just drop in, or does it need some persuasion?
> 
> *i am really excited to have a single-cell solution for my QT2L-X*



Been running my QT2L-X and QP2L-X with the 16650 so years now and very satisfied with the performance of the KP battery. :thumbsup:


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## RWT1405 (Jun 19, 2015)

Can anyone tell me if the Opus BT-3100 v2.2 will charge the 16650 cells? I have one ordered (BT-3100 w/ 18650's), but after learning more about 16650's, I'd like to try a couple. Just wanted to know if I will need another charger, or if the BT-3100 will work. Thanks!


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## RI Chevy (Jun 19, 2015)

If it can charge 18650 cells, then it can charge 16650 cells.


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## SVT-ROY (Jun 20, 2015)

Just got a few Keeppower 2500's. Charging them now on Xtra panzer. Excited to see what's what.


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## RI Chevy (Jun 20, 2015)

They work fine, just like using 2 x CR123A's.


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## RWT1405 (Jun 20, 2015)

Thank you for the prompt answer RI Chevy!


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## Jash (Sep 16, 2015)

I just ordered one for my QT2L. Been using some AW IMR 16340's, but I wanted to use them in another light (QT2A-X head on 123 body for use as a pocket rocket!).


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## HistoryChannel (Oct 25, 2015)

RWT1405 said:


> Can anyone tell me if the Opus BT-3100 v2.2 will charge the 16650 cells? I have one ordered (BT-3100 w/ 18650's), but after learning more about 16650's, I'd like to try a couple. Just wanted to know if I will need another charger, or if the BT-3100 will work. Thanks!



Hello. I have the Opus BT-C3400 and I can tell you that you can charge the Keeppower 16650 BUT it will only charge it to 4.2v.

The 16650 can take up to 4.35v so I use my Xtar VP2 and set it for 3.8v charging which cuts off at 4.35v. I love my Xtar VP2 because it can charge my 3.0v LifePO4 cells (3.6v cutoff), 3.6v (4.2v cutoff) and 3.8v (4.35v cutoff) cells. 

I have the 2500mah Keeppower 16650 cells and tested them with the Opus BT-C3400 and it's a bit disappointing. It's around 2000-2100 mah. But that may be due to the fact it's charging to 3.6v specs (4.2v cutoff) and not the 3.8v (4.35v cutoff)? That's my guess. 

The Opus charger is awesome and I chose that over the others (Maha, LaCrosse, etc) because it can charge Ni-MH, Li-Ion, LifePO4 AND when it's done charging... It does a trickle maintenance charge( around 24-34ma) on Ni-MH batteries to keep it full unlike others that cut off and the battery can self discharge sitting in the charger.

The Keeppower does have protection circuit however and it seems to only want to charge to around 4.30v before it kicks in and cuts off the charger. So it misses the mark by .05v.


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## HKJ (Oct 25, 2015)

HistoryChannel said:


> Hello. I have the Opus BT-C3400 and I can tell you that you can charge the Keeppower 16650 BUT it will only charge it to 4.2v.



What if you switch the internal switch to 4.35 volt?



HistoryChannel said:


> The Opus charger is awesome and I chose that over the others (Maha, LaCrosse, etc) because it can charge Ni-MH, Li-Ion, LifePO4 AND when it's done charging... It does a trickle maintenance charge( around 24-34ma) on Ni-MH batteries to keep it full unlike others that cut off and the battery can self discharge sitting in the charger.



The trickle charge is bad for LSD cells like eneloop.



HistoryChannel said:


> The Keeppower does have protection circuit however and it seems to only want to charge to around 4.30v before it kicks in and cuts off the charger. So it misses the mark by .05v.



The protection kicks in before the CV phase, this means you need to charge with a low charge current to get the most energy into the cell.


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## RI Chevy (Oct 25, 2015)

You may want to double check your max voltage. This base cell is not a 4.35v cell. It is a 4.3v max cell.


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## reppans (Oct 25, 2015)

The newer Keeppower 2500mah 16650 is based on the Panasonic/Sanyo UR16650ZTA cell, which specs 4.35v on the base cell. However, there is a specific note for the protected version on the Illumn site stating:



> Please Note: The internal cell is capable of being charged to 4.35V, but the protection circuit is set to 4.20V, we did not notice a huge capacity difference with this.



Mine has seen 4.27v in CV mode from a CH1 without tripping.


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## RI Chevy (Oct 25, 2015)

HKJ's first post shows 4.3v max in the graph.


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## Phlogiston (Oct 25, 2015)

I'm not surprised to see these cells charging to 4.27V or even 4.3V, 4.2V protection circuit or not. 

Bear in mind that the acceptable tolerance on charging to 4.2V is ±0.05V, and the protection circuit will have a tolerance of its own. It wouldn't surprise me if the protection circuit tolerance was also ±0.05V. 

Given that this is the case, the protection circuit will be targeted on a trip voltage somewhere in the range of 4.25V to 4.3V. This ensures that it will still allow charging to 4.2V in the worst case of low tolerance, and perhaps a bit more for chargers that go a little high but stay within the acceptable range. 

It has to be this way; if the protection circuit were targeted on 4.2V, you'd have cases where users were unlucky enough to get a cell with a protection circuit whose trip voltage was as low as 4.15V. Cue unhappy users and returned products. 

Of course, this means that the protection circuit could allow charging to a voltage as high as 4.35V in the worst-case combination of manufacturer decisions and high tolerance. 

That's the reason why one should never rely solely on a protection circuit to terminate charging, as some of the worst charger designs and ill-advised improvisations do. 

The protection circuit is not there to regulate a normal charge; that's the charger's job. 

The protection circuit's job is to help safeguard the cell's user in the event of a potentially catastrophic problem, such as an outright charger failure (e.g. a short-circuit dumping the full 5V or 12V power supply voltage across the cell) or a user error (e.g. accidentally installing a cell with reversed polarity in a set of three or more cells in series). 

From that perspective, it doesn't matter if the protection circuit permits a slight overcharge, despite the fact that this will shorten the cell's service life, and compromise its safety in use if the overcharge is repeated too often. It's just like the way a household fuse rated at 13A might not blow until 13.5A, but that's not an issue as long as it's guaranteed to blow in the event of a short-circuit (which will try to draw a great deal more than 13.5A). 

Personally, I rather like the idea of a 4.35V cell with a 4.2V protection circuit. I'd happily charge it to 4.2V every time, trading a bit of capacity for the noticeably longer service life and slightly increased safety of not charging it right up to its rated limit.


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## reppans (Oct 25, 2015)

Phlogiston said:


> Personally, I rather like the idea of a 4.35V cell with a 4.2V protection circuit. I'd happily charge it to 4.2V every time, trading a bit of capacity for the noticeably longer service life and slightly increased safety of not charging it right up to its rated limit.



Yes agree on extra PC tolerances and I also like the idea of the higher voltage cushion, particularly with certain chargers like the Klarus CH1 which has a high CV. 



RI Chevy said:


> HKJ's first post shows 4.3v max in the graph.



The cell in discussion over the few posts/day or so is the upgrade/later 2500mah version, not the earlier 2000mah version HKJ has tested. Maybe not the perfect thread for it, but also not too far off topic.


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## HistoryChannel (Oct 25, 2015)

HKJ said:


> What if you switch the internal switch to 4.35 volt?
> 
> The trickle charge is bad for LSD cells like eneloop.
> 
> The protection kicks in before the CV phase, this means you need to charge with a low charge current to get the most energy into the cell.



Thank you! I thought about changing the BT-C3400 to 4.35v but I charge a lot of 18650's and use the Xtar for 16650s. 

I did not know that maintenance trickle charge is bad for LSD batteries!!! I'll stop doing that from now on. 

I will try and charge using .25a to see if I can squeeze in every last ounce of energy into there.... Makes sense now. It usually trips around 4.29-4.3. I have never gotten it above 4.3v. I think it trips earlier if I'm charging at a higher rate. 

Thanks everyone for this awesome discussion!


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## blanex1 (Apr 16, 2016)

i just ordered a pair of these keep power 16650 battery's to run in some of my surefire's 6p's! i'll be charging on a nightcore D2,from what i have read! they should work nicely in some other flashlights i have also,by the way there coming from germany,as it was the only place to find in stock!


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## recDNA (Jan 10, 2018)

My charger will stop at 4.2 volts no matter what and that is ok with me. That said what is the max safe charging amps? I charge at .5 amps but it would be easier to charge at 1 amp if it is within spec.


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