# New Efest 18650's - confusion



## KB_314

Hey guys - I still have much to learn about batteries so this is probably a "noobish" question..

The new 2800mah efests - seems that the continuous discharge is 20A, and it's the max continuous discharge that is 35A. Pulse is very much higher still. Whereas the new 2100mah efests boast a 30A continuous discharge and a 38A max continuous discharge.

Am I right in saying that it's actually the 2100mah batteries that are comparable to VTC4's (which state a 30A continuous discharge), and the 2800mah batteries are really more like the previous 2500mahs, but with slightly longer battery life and higher pulse discharge?

In a mech, or a Reo, the VTC4's seem like they hit harder than the old purple efests. Would the same be true if comparing the 2100 vs the 2800 new efests?

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## Andre

According to the wrapper on the new Efest 2800s the continuous discharge rate is 35A (pulse is 80A) - so beats all of those you mentioned above? Do you have better information?

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## KB_314

Andre said:


> According to the wrapper on the new Efest 2800s the continuous discharge rate is 35A (pulse is 80A) - so beats all of those you mentioned above? Do you have better information?


From what I can see, continuous discharge is actually 20A, max continuous discharge is 35A (sorry, I said 30A max, but it's actually 35A). 

Efest IMR 18650 LiMn 2800mAh Battery – Flat Top – 35 Amp

Dimensions: 66mm (L) x 18mm (D)

35 Amps discharge current, great for mech mods and sub-ohm builds

*Manufacturer’s listed Specifications:*

•Rated Capacity: 2800mAh

•Nominal Voltage: 3.6V

•Voltage at end of Discharge: 2.5V

•Max Charging Current: 4A

•Standard Charge: 2A

•Max. continuous discharge current: 35A

•Continuous discharge current: 20A

•Pulse discharging current: 80A

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## KB_314

And here are specs for the 2100's..

Efest IMR 18650 LiMn 2100mAh Battery – Flat Top – 38 Amp

Dimensions: 66mm (L) x 18mm (D)

*Manufacturer’s listed Specifications:*

•Rated Capacity: 2100mAh

•Nominal Voltage: 3.6V

•Voltage at end of Discharge: 2.5V

•Max Charging Current: 4A

•Standard Charge: 2A

•Max. continuous discharge current: 38A

•Continuous discharge current: 30A

•Pulse discharging current: 60A

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## Matt

Saw the same specs the 35a is false advertisement (again). The continuous 20a is the industry's standard for all batteries. 
Besides that efest is a rewrap company so for them to have batteries that out preform others they should have there own factory and to then out preform lg samsung and sony with all there years of knowledge is very unlikely.

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## KB_314

Matt said:


> Saw the same specs the 35a is false advertisement (again). The continuous 20a is the industry's standard for all batteries.
> Besides that efest is a rewrap company so for them to have batteries that out preform others they should have there own factory and to then out preform lg samsung and sony with all there years of knowledge is very unlikely.


Thanks @Matt - I thought as much. The "too good to be true" 2800's are indeed too good to be true. But the 2100's may be comparable to Sony's if the stats are accurate (I think the 2800's are re-wrapped LG's, not sure bout the 2100's though)


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## Andre

Ah, I see, thanks for sharing this most interesting information. 

As far as I know (and I could certainly be wrong) the continuous discharge rating thus far have always referred to maximum continuous discharge rating, i.e. you can continuously discharge your battery at the maximum of the stated current. First time I have seen it indicated as you show. 

Would be interesting to know what the difference is between the max rate and the non-max rate? Grammatically I cannot see a real difference between the 2 terms. Maybe Efest is playing false with us again.

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## KB_314

Andre said:


> Ah, I see, thanks for sharing this most interesting information.
> 
> As far as I know (and I could certainly be wrong) the continuous discharge rating thus far have always referred to maximum continuous discharge rating, i.e. you can continuously discharge your battery at the maximum of the stated current. First time I have seen it indicated as you show.
> 
> Would be interesting to know what the difference is between the max rate and the non-max rate? Grammatically I cannot see a real difference between the 2 terms. Maybe Efest is playing false with us again.


It looks like that's the case @Andre - it seems like (and I can certainly be wrong here too) the 2800's are the usual 20A continuous discharge. The 2100's are the equivalent of the 30A continuous discharge - but VTC4's (30A continuous) are also only 2100mah, so nothing special about these either I guess. I don't think I will be rushing to get these at this point


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## Matt

Andre said:


> Ah, I see, thanks for sharing this most interesting information.
> 
> As far as I know (and I could certainly be wrong) the continuous discharge rating thus far have always referred to maximum continuous discharge rating, i.e. you can continuously discharge your battery at the maximum of the stated current. First time I have seen it indicated as you show.
> 
> Would be interesting to know what the difference is between the max rate and the non-max rate? Grammatically I cannot see a real difference between the 2 terms. Maybe Efest is playing false with us again.



I have never seen the 2 different rating with any other manufacturer beside efest. So to me it looks like a grammatical marketing trick.

Reactions: Agree 1


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## Andre

KB_314 said:


> It looks like that's the case @Andre - it seems like (and I can certainly be wrong here too) the 2800's are the usual 20A continuous discharge. The 2100's are the equivalent of the 30A continuous discharge - but VTC4's (30A continuous) are also only 2100mah, so nothing special about these either I guess. I don't think I will be rushing to get these at this point


But then look at their own announcement of 14 April 2015, which says the continuous discharge rating is 35A: http://www.efestpower.com/html/9504683725.html
I shall send them an email and ask for clarification.

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## KB_314

@Hein510 - can you shed some light here?


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## Matt

Wondering if someone already removed the wrap to see wich batteries they used to rewrap.


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## Andre

Where did you get those specifications from @KB_314? I can not find them on the Efest site.


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## KB_314

Andre said:


> But then look at their own announcement of 14 April 2015, which says the continuous discharge rating is 35A: http://www.efestpower.com/html/9504683725.html
> I shall send them an email and ask for clarification.


Please share if they reply. It would also be good to understand the difference between "continuous discharge" and "max continuous discharge", and why the wrapper shows the "max continuous" and not the "continuous". Smells fishy

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## KB_314

Andre said:


> Where did you get those specifications from @KB_314? I can not find them on the Efest site.


I got them from VapeMOB website - but I've seen the same online more than once. I will try and find other sources


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## Matt

http://www.myvaporstore.com/Efest-IMR-18650-LiMn-2800mAh-Battery-35A-p/ef6502835.htm

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## Andre

Matt said:


> http://www.myvaporstore.com/Efest-IMR-18650-LiMn-2800mAh-Battery-35A-p/ef6502835.htm


Thanks, got that one from ECF as well. They are as confused as we are!
Sent an email. Shall report here should I get a response. And if I do not.

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## KB_314

Changed title of thread from "question" to "confusion" - seems that it's not just a once-off noob question afterall

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## Gazzacpt

Rumour was that efest were going to use a new MNKE cell but I haven't seen any news on a new MNKE cell so I'm confused to.


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## capetocuba

KB_314 said:


> Thanks @Matt But the 2100's may be comparable to Sony's if the stats are accurate (I think the 2800's are re-wrapped LG's, not sure bout the 2100's though)


Can't remember where I read it (few places), but the consensus is that these are Sony VTC4's.

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## KB_314

capetocuba said:


> Can't remember where I read it (few places), but the consensus is that these are Sony VTC4's.


If that's true, they are 30A CD, not 38A. (Which would put the 2800's at 20A - relative to stats provided on other batteries)


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## free3dom

I've been waiting for some independent testing to be performed on these cells and still haven't seen anything. I simply do not trust any battery manufacturer anymore as they all seem to try and confuse us with their marketing mumbo-jumbo. I do hope they give you a straight answer @Andre , but I wouldn't hold my breath - or even trust them if they do reply.

Unfortunately the testing required is way too dangerous for us laymen to perform so the wait continues - this did seem too good to be true, thanks @KB_314 for bringing this to our attention 

On the other hand, a 2800mAh cell with a 20A discharge rate is still a good battery, especially considering the cost - and the 2100mAh @ 30A is decent spec too. 

I just wish for once they'd be more straightforward about it

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## ET

Doesn't this lying about battery specs mean we can all file a class action suit?


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## Silver

Thanks @KB_314 for bringing this up

I too am confused by the two different continuous discharge ratings. Strange
Looking forward to clarification. Thanks for sending a message to them @Andre 

Anyhow, for mechanical users, what I am more interested in is the curve which shows how much *usable mah* there is between 4.2 Volts and say 3.7 Volts where i would change the batt. At say a 8 amp draw, which is about 0.5 ohms resistance. And also at 4 amp draw, which is about 1 ohm resistance

Although these batteries are rated at 2800 mah, we typically dont even use a third of that before the voltage comes down to a point that the batt needs to be swapped out.

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## DoubleD

Silver said:


> Anyhow, for mechanical users, what I am more interested in is the curve which shows how much *usable mah* there is between 4.2 Volts and say 3.7 Volts where i would change the batt. At say a 8 amp draw, which is about 0.5 ohms resistance. And also at 4 amp draw, which is about 1 ohm resistance
> 
> Although these batteries are rated at 2800 mah, we typically dont even use a third of that before the voltage comes down to a point that the batt needs to be swapped out.



Same here, I'm waiting on Peg to get his hands on these batteries. 
We need charts man, charts! Give us charts

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## johan

Did some tests on one of the new efests end of last week. Will submit some info as soon as Helkom restored DSL.

via Tapatalk

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## DoubleD

johan said:


> Did some tests on one of the new efests end of last week. Will submit some info as soon as Helkom restored DSL.
> 
> via Tapatalk



Awesome  Thank you @johan , I'm looking forward to it.

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## free3dom

johan said:


> Did some tests on one of the new efests end of last week. Will submit some info as soon as Helkom restored DSL.
> 
> via Tapatalk



Great news, really looking forward to your findings 

On the other front, sorry to hear about the DSL. I was wondering why you've been so quiet lately - I was starting to miss you


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## ET

Dankie meneer, vertrou jou bevindings meer as die intawebs


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## johan

Busy typing a huge love letter (more like editing out technical jargon) regarding the new Efest 2800mAh battery. Here's a teaser (Y axis = Battery voltage under constant load & X axis = time in hours):

​

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## johan

free3dom said:


> Great news, really looking forward to your findings
> 
> On the other front, sorry to hear about the DSL. I was wondering why you've been so quiet lately - I was starting to miss you



Now you don't need to miss me anymore  - it took Helkom over 1550 new forum posts to restore DSL connection .

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## johan

ET said:


> Dankie meneer, vertrou jou bevindings meer as die intawebs



Ek gaan hierdie boodskap uitdruk en vir my vrou gee .

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## free3dom

johan said:


> Now you don't need to miss me anymore  - it took Helkom over 1550 new forum posts to restore DSL connection .



Finally 

I think new forum posts as a measure of time should be the standard 



johan said:


> Busy typing a huge love letter (more like editing out technical jargon) regarding the new Efest 2800mAh battery. Here's a teaser (Y axis = Battery voltage under constant load & X axis = time in hours):
> 
> View attachment 27831​



That looks promising...looking forward to the love letter


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## JW Flynn

some stats on the website below with regards to these pretty good looking batteries....

http://ukvapers.org/Thread-35A-Efest-2800mAh-18650-battery

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## Philip

Anyone have any opinion on the purple Efest IMR18650 3.7v Li-Mn 3100mAh 20A?


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## free3dom

Philip said:


> Anyone have any opinion on the purple Efest IMR18650 3.7v Li-Mn 3100mAh 20A?



It's a great battery...just keep the coil resistance in the higher range (0.7 and up) and <50W and they work like a charm...nice battery life

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## johan

​
I received one of the new purple wrapped Efest batteries from @Philip Dunkley about 2 weeks ago, which he obtained from SkyBlue. Only once I accepted the gifted battery I was told its for testing purposes . I decided to cycle the battery 5 times in my Reo before conducting the tests - afterall, its the right thing to do. During the cycling times what surprised me was the fact that I would vape +/-4 to 5ml of ejuice before I taste a diminishing in flavour and vapour density (aka _The Vaper's battery test method_). With all my other batteries (LG, fAW, Efest etc.) I could to date only do 3ml (_when sober_). Customery I would take out the battery and measure the voltage after x-ml of ejuice vaped and was astounded by the readings: Cycle 1 = 3.72V, Cycle 2 to 5 = 3.71V. On all my other batteries it will be +/-3.83V when discharged battery is replaced with a "fresh" one. This really wanted me to do some testing, especially the internal resistance (as that IMO is one of the most important specs of any type of battery).

Firstly, I fully charged the Efest 2800mAh (35A) battery with a Lab power supply: 4.225V constant voltage & 1.0A constant current. The battery was rested at room temperature for +/-2 hours. I had to make do with what was at hand regarding testing equipment as some of the stuff I needed are already en route to Dublin in a container.

Make do setup (_that adjustable constant load in picture is over 30 years old and bound for the bin_):




4
​
The first test conducted was to determine *internal resistance* (IR). The official Efest data sheet claimed: <10 milliohm ("initial impedance"). PS. For all practical purposes in these direct current (DC) tests, impedance = resistance.

Procedure:

Measure battery voltage without load (VNL)
Measure resistance of constant load (RL)
Measure current (Ic) when constant load is connected to battery (<100ms)
Measure battery voltage under constant load (VL)

Calculate internal resistance: IR = (VNL - VL) / Ic
IR = (4.21 - 4.18) / 0.751
IR = 0.040 Ohm (or 40 milliohm)

0.04 Ohm is extremely good compared to other batteries in my vape box, but still much higher than the claimed <0.01 Ohm - and thats is maybe why they added the term "initial" in their data sheet. Just out of interest, here are some measured IR's from various other brand batteries tested:

Efest 3100mAh (last year's generation) = 0.15 Ohm
fAW 2000mAh = 0.11 Ohm
LG IMR 2400mAh - 0.10 Ohm

Above test answered my question why I could vape the extra 1 to 2ml, compared to other batteries.

Internal battery resistance is the gatekeeper that, to a large extent, determines the "runtime". The lower the resistance, the less restriction the battery encounters in delivering the needed power. The internal resistance (IR) of a battery is defined as the opposing force to the flow of current within the battery. There are two basic components that impact the internal resistance of a battery; they are; electronic resistance (internal and external conductors) and ionic resistance (electrolyte and di-electric).

The battery cell's internal resistance levels are highest at low state-of-charge and immediately after charging. Contrary to popular belief, the best battery performance is not achieved immediately after a full charge but following a rest period of a couple of hours.

The internal resistance of a cell is closely related to its capacity and can, therefore, be used to predict the cell’s performance during a discharge. Even though there is a close correlation between a battery cell’s internal resistance and its capacity, it is not completely linear. The resistance measurement is, therefore, not used as a direct indicator of capacity, but, rather, as a warning indicator that signals if a cell has deteriorated to a level that will affect the operating integrity of the system. Field testing on all types of batteries has proven that, if a cell’s internal resistance increases to more than 25% above its known good base line value, that cell will fail a capacity test.

Next I moved over to the *capacity* (C) test of the battery to compare against the datasheet claim of: "2800mAh typical".

Procedure:

Charge battery as above and rest for 2 hours

Connect to constant current load (751mA)
Note exact time when battery voltage discharge to 2.50V
Calculate battery capaity: C = Load x t
C = 0.751 x 3.57
C = 2.68107Ah (or 2681mAh) - this is acceptable to me.








Time (hour:minute:second) period // discharge voltage under constant load:

0:00:00 = 4.21V
1:14:43 = 3.70V
2:27:53 = 3.50V
3:11:37 = 3.30V
3:24:10 = 3.00V
3:34:20 = 2.50V

It would be unfair to do comparative capacity tests of the other batteries I have on hand due to the difference in age and hence cycle history.

Unfortunately I don't have any bigger constant load than 44W to double check the 35A continuous discharge current and/or the 80A pulse discharge claims according to the data sheet and I don't really doubt the claims either. I did take some measurements with a 0.4 Ohm constant load over a period of 10sec to determine the voltage drop compared to other batteries on hand.​
New Efest 2800mAh @ 10.5A constant load over a 10sec period, showed a voltage drop of only 0.58V at the 10sec mark compared to an average of 0.87V on all other batteries tested. The rise in internal resistance was a mere 0.02 ohm under load.

In summary, I am really impressed with this battery, whether re-wrapped or not. Battery capacity (mAh) in the vaper's world, is definitely not the alpha and omega, check the internal resistance on the data sheet  before you buy.

Officicial data sheet of new Efest 2800mAh battery attached.

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## Rob Fisher

Oh WOW! That's all above my pay grade but it looks to me like these batteries are a winner!

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## johan

Rob Fisher said:


> Oh WOW! That's all above my pay grade but it looks to me like these batteries are a winner!



No its below your pay grade, I only got paid a now used purple battery, not blue screw drivers .

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## free3dom

Amazing post @johan 

This taught me more about battery operation than all the other combined research I've done...not to mention the fact that you've shone a great deal of light on the performance of these batteries.

So the bottom line is that they are great, even if they don't fully live up to their printed specifications (which are just marketing numbers in a sense, from what I've learned by reading your post).

I have had a similar experience to you - they do seem to last noticeably longer before I sense a drop when using them on my Reo (about 4-5ml @ 0.7Ohm). I foolishly put that down only to them being newer, but now I know better

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## DoubleD

Wow, great post, very informative, thank you @johan 
And now I learnt something new:


johan said:


> The battery cell's internal resistance levels are highest at low state-of-charge and immediately after charging. Contrary to popular belief, the best battery performance is not achieved immediately after a full charge but following a rest period of a couple of hours.


I need to start including a rest period between battery changes
Going on your results this is definitely my next purchase.

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## Philip Dunkley

@johan WOW, when I handed this over, all I was really expecting was a good or bad answer. This is very impressive, thank you so much for such detailed information!!! At least we have an idea now, that once again there is marketing blurb but that they are also great batteries!! These will become my defacto going forward. Thank you again mate
@Melinda and @Derick , you can sleep soundly now knowing that the new batteries are great!!!

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## Silver

Wow @johan

Superb write up and test!

Thank you so much!! You are a winner!

These batteries sound great

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## Andre

Thank you @johan. Most impressive. Together with the test @JW Flynn linked above, seems this is a great buy. 

And, if I understand correctly, the terms "maximum continuous discharge current" and "continuous discharge current", which confused us on the first page of this thread, are the same and can be regarded as 35A. I have not received an answer from Efest in this regard.

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## johan

Andre said:


> Thank you @johan. Most impressive. Together with the test @JW Flynn linked above, seems this is a great buy.
> 
> And, if I understand correctly, the terms "maximum continuous discharge current" and "continuous discharge current", which confused us on the first page of this thread, are the same and can be regarded as 35A. I have not received an answer from Efest in this regard.



According to the official Efest data sheet there is no mention of the confusing: "_maximum continuous discharge current_" and "_continuous discharge current_". Yes you are correct in your assumption: continuous = 35A maximum [and pulse (smaller /equal to 1sec period) = 80A].

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## zadiac

I decided to wait a while to post my opinion on these batteries. I've been using them now for about 3 weeks or so and I just bought two more yesterday at VapeCon.

I concur with Ohm Johan's assessment of the longer vaping time on the Reo. Normally, with the Efest 2500 and the Samsung 25R I would fill my bottle only just above half and have a good vape all the way to empty, but with these I can fill my bottle to 3/4 and have the same experience right through to empty. That's saying something to me.

I don't have the electronics knowledge of Ohm Johan (his equations make my head hurt) and/or tools to test batteries properly like he does, so my above opinion is purely based on personal experience and I prefer these new ones above the old ones and the smurfs.

These new ones also keep their charge after taking them out of the charger. I've had one stand for a day and when I put it back into the charger to check, it showed 4.2 volts. The old 2500's also did that, but not my smurfs. They still go down to 4.16 after just a few hours outside the charger.

So my choice of batteries is obvious.

Again, just my opinion.

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## Silver

zadiac said:


> I decided to wait a while to post my opinion on these batteries. I've been using them now for about 3 weeks or so and I just bought two more yesterday at VapeCon.
> 
> I concur with Ohm Johan's assessment of the longer vaping time on the Reo. Normally, with the Efest 2500 and the Samsung 25R I would fill my bottle only just above half and have a good vape all the way to empty, but with these I can fill my bottle to 3/4 and have the same experience right through to empty. That's saying something to me.
> 
> I don't have the electronics knowledge of Ohm Johan (his equations make my head hurt) and/or tools to test batteries properly like he does, so my above opinion is purely based on personal experience and I prefer these new ones above the old ones and the smurfs.
> 
> These new ones also keep their charge after taking them out of the charger. I've had one stand for a day and when I put it back into the charger to check, it showed 4.2 volts. The old 2500's also did that, but not my smurfs. They still go down to 4.16 after just a few hours outside the charger.
> 
> So my choice of batteries is obvious.
> 
> Again, just my opinion.



Thanks for the feedback @zadiac
Most helpful to have a personal experience supporting Ohm Johan's findings
Now why didnt I buy any of these yesterday? Lol? Sigh...

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