SX25L3 and keeppower 3400 mah 18650 - cut off voltage at 3.30V problem

Hi i bought 10 keeppoweer 3400mah 18650 but have a big issue. I bought them because as specifications they cuts off at 2.50V, but with my eagletac SX25L3 in turbo that uses 3 18650 in series, one battery cuts off at only 3.30V !!!
I know when in use they are stressed up and the voltage drops lower than 3.30, but it must to drop from 3.30 to 2.50v and it is about 0.80V!!! this would be that a standard protected battery tath cuts off a 2.80V would cuts the power at 3.60v in this torch.

In this case or specifications are not correct for this PCS, or there is an issue on the battery.

PS: to prevent damages or explosion i charged all 3 18650 at the same voltage

Let me know
thank you

Have answered your pm

reply me on the forum so other people can read and reply too
This is your reply:

For what I understand it a protection-board problem. It can't be the battery since that only provides power and doesn't have a brain which controls the cut-off.

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and mine too:

Sure i think that the problem would be the PCB that control the cut off. So do you think with your experience that the problem is the PCB and is not normal to cut off at only 3.30V under stress? BUt I tryed 6 batteries and all are the same.

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Try with other brand batteries. Know cut-off point of the flashlight?

I don't know the cut off of the flashlight, but it didn't cuts off, but the battery because to reactivate i have had to put in charge the battery (he indicates 0.00V)
I have no other batteries brand so can not try.

I'm running the same setup and I haven't had any issues. I wouldn't discharge past 3.7V/cell anyway, so if your cutoff is below that I would say it's a good thing. If it's doing it reliably, it sounds like it's operating as designed, and it will help you get a good life out of your cells. The batteries cut off to protect themselves at 2.5 but they are well past dead at that point.

what flashlight and batteries do you have and tested whith? Shall you try to run the sx25l3 in turbo mode and wait your batteries to cut off? than can you put in charge to reactivate it and measure the remain volfotage? is at 3.30v or a lower voltage? Believe I have paid 130 eur for these keeppower and the reason i choosed them is the lower cut off at 2.50V, but in real life the use of these battery is completly different as i imagined. I know they can last more years, but there is not necessary because i can charge them at no more than 4.00v. Please let the test and let me know. Thank you buddy

As I mentioned, I'd rather not intentionally drain my batteries to 3.3V, but I'll put it on my bench power supply tomorrow and report on the low voltage cutoff. I have an SX25L3 MT-G2.

Normally I will recharge or replace my batteries when the low voltage warning starts, or when they dim or drop out of regulation, depending on the light. Also, if you aren't going to use it right away, charging to 4.0-4.1V is better than 4.2.

At 3.3 volt out of the light the batteries the batteries are Dead, empty, done for, time to recharge. Once you apply any decent load the voltage drops past the 2.5 cutoff.

Check out this page to see how much energy is left at a given voltage.

http://lygte-info.dk/info/BatteryChargePercent UK.html

I installed other 3 pieces of keeppower 3400 and draining in turbo, they cuts-off at 2.85v instead 3.30v like other 6 pieces. Something wrong with the PCB?

plata0190 said:

I installed other 3 pieces of keeppower 3400 and draining in turbo, they cuts-off at 2.85v instead 3.30v like other 6 pieces. Something wrong with the PCB?

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Maybe you got a couple bad cells? If one cell trips (perhaps because it is unbalanced when compared to the others), it makes the load that much greater for the others. First of heard of anyone having a similar problem with Keeppower 3400s, but a defect is always possible.

Given that the last three you tried worked fine, it definitely sounds like it isn't a problem with the light, but with some of the cells you bought. Can you test them individually, perhaps in a single 18650 light, and see how they compare?

A friend of mine gived me 3 new soshine 3400 protected where cuts-off at 2.80V as you can see on their site.
Comparing to my keeppower 3400 i have made the same test and when the sx25l3 discharged them fully in turbo, i measured them after 30 seconds and voltages was 2.84 - 2.84 - 2.82. How is possible that even the PCB cuts-off at 2.80 the remaining voltage in idle is 2.84? and more important think how is possibile that keeppower instead cutting off at 2.55 their cut off is the same as soshine or more? I don't understand

plata0190 said:

...i measured them after 30 seconds and voltages was 2.84 - 2.84 - 2.82. How is possible that even the PCB cuts-off at 2.80 the remaining voltage in idle is 2.84?

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Voltage sags under load...so if it cuts off at 2.80, it will always be a little higher than that once you stop drawing power from the cells. Also, there is some variation in the voltage cutoff, most cells specify an average voltage, and also a range. I.e., 2.80V +- 0.05. So anything from 2.75 to 2.85 would be completely normal, and no cause for concern.

plata0190 said:

and more important think how is possibile that keeppower instead cutting off at 2.55 their cut off is the same as soshine or more? I don't understand

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Have you checked the cutoff in a single cell light, as I suggested earlier? Maybe you got a defective cell, or maybe there is something else going on, but until you give more data, all we can do is guess.

Also, you should read Jay T and electromage's posts. Not a good idea to drain cells to the cutoff every time...it will likely decrease the life, and performance of your cells. The amount of extra runtime is small (cells are pretty well done long before 2.8V) and it is much harder on the cells. Also, protection can fail. Better to top off, than to run them down to nothing, even for protected cells.

I've got no idea what you are using to measure the voltage of the cells, but the difference between 2.84 and 2.80 volts is nothing. Your meter probably has a variance of =/_ 2-5% for it's reading in that low of a range.

As for the Keeppower 3400's, you need to use a piece of equipment like the Accucel-6 to charge then discharge the cell to find what you really have. The PCB used to regulate the batteries could have a fault, but without a controlled test, we're all peeing in the wind.

The only information that I can find on the Keeppower batteries isn't on Keeppower's website, but on Budget Lights forum posted by HJK. If you have that much of a concern about the batteries, contact Keeppower, describe the issue your having and see what they have to say.

I have no flashlight with single 18650 slot, so can't proceed. Im using a standard digital multimeter, and just changed his battery with a new one so, measures are true. Variance from 2.84 and 2.80 is nothing, i quote it, but as you told me i suspect too the keeppower PCB is faulty. What i can not understand is how is possiblle that keeppower with a cut-off at 2.50 (+/- 0.05) cuts off at 2.85v and soshine with a PCB where cuts-off at 2.80 (+/- 0.05) cuts at the same voltage: 2.84?

plata0190 said:

Im using a standard digital multimeter, and just changed his battery with a new one so, measures are true. Variance from 2.84 and 2.80 is nothing, i quote it, but as you told me i suspect too the keeppower PCB is faulty. What i can not understand is how is possiblle that keeppower with a cut-off at 2.50 (+/- 0.05) cuts off at 2.85v and soshine with a PCB where cuts-off at 2.80 (+/- 0.05) cuts at the same voltage: 2.84?

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Where did you see that the Keeppower battery is supposed to cut off at 2.5 volts? The protection cut off listed on the other site appears to me to be showing somewhere around 2.8 volts.
Borrowed from BLF posted by HKJ

If you are going to cite information, please list where it came from so we're all on the same page.

Just google it and you will find. I red the cut off here http://lygte-info.dk/review/batteries2012/Keeppower 18650 3600mAh (Black) 2014 UK.html and was confirmed me by keeppower.

The brand told me is a strange problem and they are looking up to this.

plata0190 said:

Just google and you will find. I found it here http://lygte-info.dk/review/batteries2012/Keeppower 18650 3600mAh (Black) 2014 UK.html and confirmed by keeppower

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The cell that you are linking to isn't the 3400 mAh version, it's the 3600 mAh version.
Secondly, the tester, (I'm assuming HJK since that site appears to have removed any credit for the person performing the testing) states for the 3600mAh cell that he COULD have gone down to 2.5 volts, but didn't. That's not Keeppowers official position on their battery.

Why do you insist on cherry picking portions of tests done that aren't the same cell as the one you are questioning?

NoNotAgain said:

The cell that you are linking to isn't the 3400 mAh version, it's the 3600 mAh version.
Secondly, the tester, (I'm assuming HJK since that site appears to have removed any credit for the person performing the testing) states for the 3600mAh cell that he COULD have gone down to 2.5 volts, but didn't. That's not Keeppowers official position on their battery.

Why do you insist on cherry picking portions of tests done that aren't the same cell as the one you are questioning?

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He isn't cherry picking...Keeppower doesn't list the cutoff voltage on their site, but you can find it elsewhere. HKJ (not HJK) gets the stated claims from the manufacturer, I believe. Just because he doesn't test to 2.5V, doesn't mean Keeppower doesn't rate it to 2.5V.

Furthermore, the link you posted is a test of high current, not the low discharge voltage cutoff. It has nothing to do with the question at hand.

You are right to point out the 3600 mAh version is a totally different cell...but in this particular case, the low voltage cutoff is the same.

thedoc007 said:

He isn't cherry picking...Keeppower doesn't list the cutoff voltage on their site, but you can find it elsewhere. HKJ (not HJK) gets the stated claims from the manufacturer, I believe. Just because he doesn't test to 2.5V, doesn't mean Keeppower doesn't rate it to 2.5V.

Furthermore, the link you posted is a test of high current, not the low discharge voltage cutoff. It has nothing to do with the question at hand.

You are right to point out the 3600 mAh version is a totally different cell...but in this particular case, the low voltage cutoff is the same.

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thedoc007,

The OP stated that he had issue with the trip voltage of the Keeppower 3400mAh cell. My first post showing the trip voltage was from a test that HKJ performed. The second post by the OP of the 3600mAh cell was mixing apples and oranges.

I find it rather interesting the Keeppower doesn't have any "real" information on their website on the cell performance. If the are relying on HKJ for data they should be able to link to his testing instead of expecting patrons to sort out the real from the unknown.

If you look at the bottom of the website referenced, ( http://lygte-info.dk/review/batteries2012/Keeppower 18650 3600mAh (Black) 2014 UK.html ) HKJ has a series of charts listing trip voltages of cells not manufactured by Keeppower that are identical to what is posted for the Keeppower cells. It appears to me that HKJ does the testing since he goes into detail on the test and setup.

Anyhow, I've PM'd HKJ to see if he can sort out what testing he performs and what data he uses from the manufacturer.

"Notes and links

The battery 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"