Fenix TK75 runtime with NCR 3400mah PCB

Greetings to all. I just need to compare other peoples experiences with these batteries and being used on the specific flashlight (or similar) . Right now, although I am very impressed with the power of this flashlight I am very disappointed with the running time.
I thought I'd buy some of the best batteries on the market (Panasonic 3400mah) and also I have some LG2600mah with no PCB for back-up. You are probably wondering what results I am getting right? well with the NRC's about 30 minutes on turbo and less than 25 mins with the LG's. that's right, around 30 mins instead of the 1h & 15 mins that the manufacturer claims!! its also very difficult to test the flashlight on turbo mode due to the heat. it gets really hot!! I think 10 mins at a time is more than enough. I didn't get at 15 mins continuous running time because I want to take care of my flashlight ( I guess that the 150 euros + that I paid for it is a constant reminder of how careful I have to be with it).....
As you would expect all the other modes, high and medium (who cares about low mode right? ) have significantly reduced running times. I didn't have much time to test it more to get exact figures because I sent it to China for repairs (bad led needs replacement). I am trying to convince them that there is a problem with the electronics and that I would prefer I replacement.
I mean, its not possible that you could get these numbers with the Panasonic batteries due to them having a PCB? I believe that the LG's with no PCB prove this.
And if its a problem with the batteries please tell me what batteries will let me have more than 1h and 15 mins runtime so I cant get them !!!

Depending on the 2600lm (20min) or 2900lm(15min) step downs,you should get 3 or 4 full runs of turbos on 3400mah cells. Also there are extenders available which will more than double your run time. As with all lights though your hand holding the light is the best judge of heat,if too hot to hold step it down a level or 2.

Capolini (roberto)on here has done lots of run times,have a search on here and:welcome:

Thanks. I have the 2900lm version. I am not even getting 2 full runs on turbo. anyway I asked fenix to check it out. There is no doubt that there is a problem with the specific flashlight. I guess that happens sometimes

The manufacturers claims are with step down,so 2900lm for 15 ish mins,then steps down and the rest of the time running it taken so very misleading(as with most manufacturers).

I have used both 3400mAh Orbtronic and NCR 3400mAh cells in my TK75.

I was able to get a COMBINED[minus step downs] 62 minutes of turbo with my Stock Original TK75[2600 Lumens] with both of those batteries.

When I got it modded[TK75vn] I was still able to get ~ 51/52 minutes of Combined turbo.

I have read about this before on here. Must be something wrong w/ the flashlight or possibly the batteries???

Capolini said:

I have read about this before on here. Must be something wrong w/ the flashlight or possibly the batteries???

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The OP doesn't talk about how he is charging the batteries and to what voltage before use. What is he using to verify the fully charged state, (charger just shuts off or monitoring via multimeter)

Are the batteries fully charged to 4.2 volts or there abouts? Is he verifying the end voltage (and what that voltage it is) and how many charge cycles have the batteries seen? Also if he's in a very warm area, once the light gets warm, it's going to step down and may not recover for sometime before turbo is available for use again.

My orbotronics and thrunites have consistently outperformed my nitecores many many times however I have seen both orbotronics and thrunite 3600 mha and may be wrong but I thought I saw 4000 thrunites but I can't be certain about that since I couldn't find them again has anyone used the 3600 or above that in the reputable brands and any comments all comments welcome


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NoNotAgain said:

The OP doesn't talk about how he is charging the batteries and to what voltage before use. What is he using to verify the fully charged state, (charger just shuts off or monitoring via multimeter)

Are the batteries fully charged to 4.2 volts or there abouts? Is he verifying the end voltage (and what that voltage it is) and how many charge cycles have the batteries seen? Also if he's in a very warm area, once the light gets warm, it's going to step down and may not recover for sometime before turbo is available for use again.

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Your right he did not mention that. You would think that he is giving them a full charge and using a voltage meter to verify that.........who knows!

It gets hot where I live in the summer. The heat never affected my TK75's ability to run on turbo. It has a TIMED step down, not a THERMAL step down. Mine never got too hot where I couldn't bump it back to turbo after the step down. Then again, I have the original TK75.The people who have listed this problem with cumulative Turbo run time being low ALL had the new version TK75[2900 Lumens]

Another thing to think about is how the capacity of the batteries is measured. I know that with Alkaline D Cell batteries they can claim 15000 mah because they pull a very low current from the battery. However the same battery can only support 3000 to 5000 mah on a higher draw. I remember reading something on one of Selfbuilt's reviews about how he didn't get a proportionate boost in runtime on a light when he switched from 2600mah AW's to 3400mah. He mentioned something about how the batteries would only be able to support the high draw of the light he was reviewing for a certain period. The advantage of the higher capacity cells was that they were able to maintain a regulated output at a lower level after they couldn't support the higher draw any more. The light would just shutdown with the lower capacity cells because the high draw had completely drained the cells. :shrug:

I don't know much about batteries, but, I suppose that most batteries that are based on the ncr 3400mah don't have much difference other than the addons, PCB's. Specs for the NCR cut-off voltage at 2.75v should be enough to power the flashlight in turbo mode.
Now about the 1 hour and 15 minutes that the manufacturer claims... they don't mention anything about increased current and how that will affect the running time of any batteries. do they? otherwise they would state that on Turbo mode " running time is approximately 30 minutes note : due to high current".
or should we ask them what special battery they are using to get these times? from what I read somewhere, they are using 2600mah batteries to time all the modes.
I have an amp meter, I measured the batts each time, it was was over 4.18 volts for each, up to 4.2v.
I even went up to 14 minutes 15 mins I think without a step down, then went for 10 minutes, and after about 5 mins (stopped timing) it stepped down to High mode. room temperature was around 25 degrees. between turbo modes I waited around 30-60 minutes for the flashlight to cool down. it got really hot.
anyway, if there is a problem with the circuit board I am going to ask for a replacement.
its very disappointing to look at the outside of the box, with the "pretty" running times and not getting even close to that.
its like buying a VW golf with 150 horsepower and only getting 50 horsepower. if that was the case I would get a bicycle.

poupi29 Said:

Specs for the NCR cut-off voltage at 2.75v should be enough to power the flashlight in turbo mode.

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Sorry,not a chance! Once the batteries hit around 3.5v to 3.60v it NO longer has the power to sustain turbo. I am positive of that. When I run it on turbo for ~60 minutes and it stepped down to high for good because of battery depletion. I measure the voltage every time after use and 3.5V to 3.60v is what it always was.

Other than that it sounds like it MAY be a defective torch.

ven said:

The manufacturers claims are with step down,so 2900lm for 15 ish mins,then steps down and the rest of the time running it taken so very misleading(as with most manufacturers).

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I understand what you are saying ven, but it looks like they are not giving out any exact numbers on performance. is it possible that each flashlight is unique and has a different performance? I think that sounds a bit dumb, it wouldn't be very professional.
I also used some older LG2600mah without PCP and I got around 20-25 minutes on turbo. I should have kept the light longer before returning it so I can do some more testing (actual testing).

Flashlight manufacturers always twist,manipulate figures as these sell,like cars do x amount of mpg for example.

too many factors from cells,how old,much resistance as this increases with age,basically you have about 0.6v of working turbo,as the 4.2v 2s2p set up the cells at 2900lm get sag,so it wont show 4.2v. at 3.8v on turbo the sag from power could bring it to 3.5 or 3.6v and step down only allowing a burst in turbo then a sustained high till the cell sags too far again.

Please note the above are just rough examples to show what happens . Once the light is off the cell partly recovers and allows turbo again,maybe for a few mins before stepping down.

All lights will have slight differences but will be in the manufacturers specs/allowances/tollerence. Try some IMR 3100 or 3200 cells in and see if you get better run times on turbo as the cell gets in the high 3v .

the 2600lm version is 20 min step dome ,presume the 2900 version is 15 min due to extra heat from the 300 lumens.

Best solution is decent cells,extension kit,then more than double your run time on turbo if needed.Most uses(unless walking capo) don't require a constant turbo

Just remember manufactures mislead and it's only true testing like Roberto that shows real world figures.these also change in the climate ,hot climates = worse run times and visa versa.

fenix are not too far out compared to other manufactures......mentioning no names nitecore...doh :laughing:

But the all do a run time on turbo including step down for their too good to be true run times.

Check self builds review ,I am sure he reset at turbo,other than that Roberto will give you real world figures out in the field....literally. :thumbsup:

Thanks everyone, you really answered all my questions/doubt's. I already ordered another set of NCR 3100. I think that's enough money spent on this flashlight, I will admire the imr batteries from a distance: p

Gentlemen, finally fenix has repaired my tk75 (changed 1 of the led bulbs) but haven't done anything about the electronics.
I told them what runtimes other people are getting with 3400mah batts (around 60 minutes) and they told me that's impossible.
this Is what their final answer was... "Also it is normal that turbo mode only works 30mins then drops to high mode. Because it produces a lot of heat and the temprature is over 60 C deg. It has to drop down in order to protect LED."
which is incorrect since temperature protection is at around 15 minutes I think, 20 mins for the 2600lm version. 30 minutes of use with cool down periods in between.... to protect the flashlight from overheating???
not a very professional answer if you ask me, since for the past few weeks the topic was about the magic number, 30 minutes, and why I cant get more total time with turbo.
are other people getting 30 minutes total turbo with rest periods in between?
anyone know how many watts the leds are or what the amperage draw is at turbo?

I am sure you will get an accurate answer but iirc 3.5A per led what rdfronty recorded.

I was hoping for a runtime with their step down not mentioned as it has been previous but found this at the fenixtorch

Brightness Levels:
Turbo: 2900 lumens - 1 hour 15 minute runtime (15 minute before dropping to 1100)
High: 1200 lumens - 4 hour runtime
Mid: 450 lumens - 12 hour runtime
Low: 25 lumens - 200 hour runtime
Strobe: 2900 lumens
SOS: 450 lumens

Note the turbo quoting the drop to 1100lm(would have thought 1200lm as thats high) but still its now mentioned!!

They (fenix) , mentioned that the temperature step down for the 2900lm is 20 minutes.
"Turbo: 2900 lumens - 1 hour 15 minute runtime (15 minute before dropping to 1100)", so if it drops to high after 15 mins and you cycle it back to turbo again, what happens? it runs out of juice and drops to high again or runs for another 15 mins on turbo?
I also asked them to add more precise details about runtimes on their site, which of course I am certain they will never do.
all this secrecy they have...

poupi29 said:

They (fenix) , mentioned that the temperature step down for the 2900lm is 20 minutes.
"Turbo: 2900 lumens - 1 hour 15 minute runtime (15 minute before dropping to 1100)", so if it drops to high after 15 mins and you cycle it back to turbo again, what happens? it runs out of juice and drops to high again or runs for another 15 mins on turbo?
I also asked them to add more precise details about runtimes on their site, which of course I am certain they will never do.
all this secrecy they have...

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The answer to your step down after 15mins(2900lm is 15mins/2600lm is 20 mins),is it will go back to turbo,now how many 15 minute turbo runs depends again on cells etc. So going off the 2900lm and around 60mins run time,you would expect potentially 4 step downs from initial run on turbo ..............
Then it may step up ,but for a minute and step down as the cell can not hold the turbo draw................

If this is not enough,easiest solution imo is an extension or carry more cells to swap...........