Why NiMH's for the Fenix TK 70 ?

noopy

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why does fenIX only recommend nimh battery's for the tk 70 flashlight?:party::drool: are not lipo batterys top of the line?
 

AnAppleSnail

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Because the TK70 is built for 4 D cells, and NiMH D Cells have much better performance than alkaleak D cells. This is one of those flashlights built for commonly-available batteries.

If you wanted to step outside your warranty, you could probably bodge together a 4P1S pack of 26650s. AW IMR 26650s (D size) give [email protected], or 42 watt*hours at 3.2v. 4 NiMH D cells give [email protected], or 48 watt*hours at 4.8v. This surprising result (NiMH energy > LiIon) is because the increased safety of IMR cells comes at a power disadvantage. You'd also need a very strange pack construction!
 

walterr839

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I have just started using two 32900 5000 mah LifePO4 cells in my TK 70 and so far is it great. I don't' have run times yet but it is as brighter or brighter than using 4
tenergy 10000mah NiMh D cells
 
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hyprmtr

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I bridged the sense resistors and use 3 26650 TF Flames. I also swapped out the T6 LEDs to XML-2 U2 leds though. Its very bright now!


Ken
 

noopy

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WOW thanks guys a lot of good input .. i just received my TK 70 and it is going from brightest setting down to the lower almost instantly i have only 4 alkaline battery i am waiting for my new tenergy 10000 d s to charge HURRY UP SLOW *** CHARGER!!!!
 

N8N

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yeah, your light probably thinks your batteries are dead due to the high internal resistance of the alkalines, or in other works when you turn it on high the voltage sags almost immediately. It'll probably be better with the tenergies...
 

Rexlion

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Low self discharge NiMHs like Tenergy Centuras are the best way to go. Then the light will be ready to go on max even if it's been sitting a while.

Although those 32900s sound attractive... but most Fenix lights tend to default to direct drive (nonregulated output) on overvoltage, don't they?
 

Cataract

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Low self discharge NiMHs like Tenergy Centuras are the best way to go. Then the light will be ready to go on max even if it's been sitting a while.

Although those 32900s sound attractive... but most Fenix lights tend to default to direct drive (nonregulated output) on overvoltage, don't they?

There was an Asian / China version that ran on, I believe, 26650's. you should search for the old TK70 thread.

The LSD Tenergy batteries gave me very little runtime on turbo (max 15 minutes) until they almost quit running turbo mode; that is due to the fact that D sized LSD batteries have a max output just around 9-10 amps, while the non-LSD D sized Tenergy have an output of 30-40 amps. the regular NiMh Tenergy batts were the way to go for me.

Sorry for the lack of precision on the numbers, but I'm going by memory here...
 

StorminMatt

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The LSD Tenergy batteries gave me very little runtime on turbo (max 15 minutes) until they almost quit running turbo mode; that is due to the fact that D sized LSD batteries have a max output just around 9-10 amps, while the non-LSD D sized Tenergy have an output of 30-40 amps. the regular NiMh Tenergy batts were the way to go for me.

Are you sure that your batteries weren't bad? I've actually heard others say that the Premiums and Centuras both give them about the same amount of runtime on Turbo in a TK70 (about 1:15). By the way, I have noticed that Tenergy rates the Premiums as being able to deliver a maximum current of 47.5A vs only 7.8A for the Centuras. I actually spoke to one of the engineers at Tenergy about this, as I didn't want to buy Centuras if they're even wimpier than your typical Eneloop (which can do 10A). They assured me that the Centuras could do a 5C discharge (~40A) just like the Premiums, and weren't sure why the Centuras were rated so low. But to this day, those numbers are still on the website. I should also note that measurements of internal resistance show that the Centuras actually have a slight edge compared to the Premiums.
 

Cataract

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Are you sure that your batteries weren't bad? I've actually heard others say that the Premiums and Centuras both give them about the same amount of runtime on Turbo in a TK70 (about 1:15). By the way, I have noticed that Tenergy rates the Premiums as being able to deliver a maximum current of 47.5A vs only 7.8A for the Centuras. I actually spoke to one of the engineers at Tenergy about this, as I didn't want to buy Centuras if they're even wimpier than your typical Eneloop (which can do 10A). They assured me that the Centuras could do a 5C discharge (~40A) just like the Premiums, and weren't sure why the Centuras were rated so low. But to this day, those numbers are still on the website. I should also note that measurements of internal resistance show that the Centuras actually have a slight edge compared to the Premiums.

All right, you had me unpack a box (just freshly moved) to double-check if my memory is still there... I did make a slight mistake. I currently use the Tenergy Premium (non-LSD) in my TK70, which work just fine. The batteries that did not work up to spec are Accuevolution (Accupower) 10 000 mAh LSD's (not Tenergy LSD... oops... I did want to buy Tenergy LSD's at the time, though). The accupower gave me the 1:15 runtime for a few cycles and then the runtime on turbo went down to 15 minutes and then around 15 seconds only a small number of cycles afterwards. I was told by guys who really know their stuff (local battery warehouse) that the Accupower are pretty much as good, if not the same, as the Tenergy as they are most likely made in the same facility. Those guys do know their stuff and I did double-checked a lot of their sayings and it turns out they seem to be 100% on track.

Is it possible the claims about the Centuras running fine were only a first impression, same as I got with my accupower LDS's? If you had asked me in the first week I got my TK70, I would have said buy the Accuevolution and nothing else, yet now I say don't use those in a TK70 ever (non-LSD is quite possibly fine, though).

The specs I just found rate the Tenergy Centura at 0.5C, not 5C, consistent with my personal experience and advice from the guys at the warehouse I bought all my high capacity D cells at:


  • Industrial high capacity rating for long lasting performance.
  • Advanced low self-discharge NiMH technology to maintain charge during inactivity.
  • No memory effect.
  • Replacement for Alkaline D size.
  • Can be charged up to 1000 times.*

  • Maximum Discharge Current: 1C
  • Charge Current:
    • Standard: 780mA x 16 Hours
    • Rapid: 1560mA x 7 Hours
  • Maximum Discharge: 7.8A (exact same as the accuevolution 10 000mAh LSD; too low for the TK70 @ 10-11 amps)
  • Standard Discharge: 0.2C - 0.5C

  • Weight: 145g
  • Operating Temperature: -10°C - 50°C
  • Operating Humidity: 45% - 85%
  • Storage Temperature: -20°C - 30°C
  • Dimensions: 61.5mm x 33mm (H x D)


I'm wondering where that 5C discharge rate spec came from as I just
Is it possible the Centura have an exceptionally high discharge rate for LSD's?

My actual research was limited to the guys at a specialized battery distributor and a quick check on the internet, but in all the conversations I had with them, they do seems to know their stuff. One major possible difference between you data an mine is that I use 10 000 mAh batteries

I do suspect, however, that their stocks could be a little old and the batteries might have been sitting on the shelves for well over a year
 
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N8N

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I have no experience with Accupower cells but some reading told me that they *were* highly regarded in the past but consensus seems to be that their quality has gone to crap in the past few years... so I bought Tenergy. All of mine are still on their first cycles though so I don't really have a personal opinion of them yet. Working so far though (in a light I never use, and in various meters...). Wish Panasonic would make Eneloops in C, D, and 9V formats but they seem to be concentrating on AA and AAA only.

Sent from my XT897 using Tapatalk
 

StorminMatt

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Don't know about Tenergy Centuras and Accupower being made on the same assembly line. But given the fact that the Accupower is 10000mAH and the Centura is 8000mAH, I find this somewhat doubtful. I've also heard that old Accupower batteries were good, but newer ones are not so good. As far as Tenergy Centuras, I've had mine for over a year. And they seem to be good so far. I've not seen a loss of capacity or increased self discharge in that time. Admittedly, I have not used them on anything with REALLY high current draw, though. As far as using them, I would definitely recommend you give them a try. As NiMH D cells go, they're actually rather inexpensive.
 

Cataract

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Just a quick comment so this thread does not go off track:

The main point I was bringing up was mainly the discharge rate of LSD VS non LSD NiMh D cells in regards to the high (10-11 amp) draw of the TK 70. My research and direct experience with 2 different sets of batteries -one set being LSD and the other non LSD- so far indicates that LSDs are not the way to go with the TK70. I also noticed that a lot of the online Fenix vendors (including Fenix themselves if my memory serves) did recommend and package Tenergy Premiums (non LSD NiMh) with the TK70.

The original question was about why NiMh in the TK70 and the answer is simply because they can handle the high current draw demanded by the TK70. I hope my nitpicking on the details of which type of NiMh is best for this purpose will not derail this thread into just battery discussions...
 

StorminMatt

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Just a quick comment so this thread does not go off track:

The main point I was bringing up was mainly the discharge rate of LSD VS non LSD NiMh D cells in regards to the high (10-11 amp) draw of the TK 70. My research and direct experience with 2 different sets of batteries -one set being LSD and the other non LSD- so far indicates that LSDs are not the way to go with the TK70. I also noticed that a lot of the online Fenix vendors (including Fenix themselves if my memory serves) did recommend and package Tenergy Premiums (non LSD NiMh) with the TK70.

The original question was about why NiMh in the TK70 and the answer is simply because they can handle the high current draw demanded by the TK70. I hope my nitpicking on the details of which type of NiMh is best for this purpose will not derail this thread into just battery discussions...

Then again, when you say 'two sets of LSD batteries', are you talking about two different brands? Or just two sets of the same brand? As has been said, newer Accupower D cells are known to be substandard. And that alone could be the reason why they can't do it. Of course, even if you try two different brands, that doesn't mean that NO LSD batteries are capable of powering a TK70. And the fact that Fenix sells the TK70 bundled with Premiums but NOT Centuras doesn't mean that Centuras are not up to the job. Only after actually trying the light on these batteries can this be determined.

As far as the original question, it was actually not about whether alkalines could be used, but rather why NiMH is recommended rather than Li-Ion. The answer is that lithium ion batteries could certainly be used to power a light in the brightness category of the TK70. In fact, many such lights are available (including the Fenix TK75). This particular light simply uses NiMH D batteries because Fenix wanted to make a bright light that runs on D batteries (rather than Li-Ion). And alkaline batteries don't have the oomph to run the light (as has been said).
 

Cataract

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Then again, when you say 'two sets of LSD batteries', are you talking about two different brands? Or just two sets of the same brand? As has been said, newer Accupower D cells are known to be substandard. And that alone could be the reason why they can't do it. Of course, even if you try two different brands, that doesn't mean that NO LSD batteries are capable of powering a TK70. And the fact that Fenix sells the TK70 bundled with Premiums but NOT Centuras doesn't mean that Centuras are not up to the job. Only after actually trying the light on these batteries can this be determined.

As far as the original question, it was actually not about whether alkalines could be used, but rather why NiMH is recommended rather than Li-Ion. The answer is that lithium ion batteries could certainly be used to power a light in the brightness category of the TK70. In fact, many such lights are available (including the Fenix TK75). This particular light simply uses NiMH D batteries because Fenix wanted to make a bright light that runs on D batteries (rather than Li-Ion). And alkaline batteries don't have the oomph to run the light (as has been said).

Just to avoid possible confusion from the less knowledgeable; NEVER mix battery types, brands or capacities in any appliance.

My cousin also has a TK70 and all the same batteries I have, so the experiment has been conducted twice with identical results:

I tried with 4 AccuEvolution LSD's -rated at max 7.8 amps discharge rate -same as the centura- while the TK70 is rated as pulling 10 amps by Fenix, but has been measured by CPF members to pull 11 amps on turbo; on paper, those batteries are not powerful enough to power the TK70 on turbo. Perhaps the AccuEvolution are overrated, but the numbers still don't add up for the Centura unless they are underrated, which is doubtful as the rule of thumb for LSD NiMh is (max. discharge rate = ~battery capacity). If anyone has been able to use the centuras or any LSD batteries for more than a couple of weeks in their TK70 and use turbo regularly I'm definitely interested to hear about it.

I also tried with 4 Tenergy Premiums (non LSD), rated at a max discharge rate of 47.5 amps. and those work just fine to this day. The rule of thumb for non-LSD batteries is (max discharge rate = ~ 5X battery capacity) In theory, any high capacity non-LSD NiMh D cells should be fine in the TK70 on turbo, but capacity will dictate the max runtime.

Allright, back to the topic at hand; I'm just trying to save people from expensive bad experiences.
 

eff

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Just to avoid possible confusion from the less knowledgeable; NEVER mix battery types, brands or capacities in any appliance.

My cousin also has a TK70 and all the same batteries I have, so the experiment has been conducted twice with identical results:

I tried with 4 AccuEvolution LSD's -rated at max 7.8 amps discharge rate -same as the centura- while the TK70 is rated as pulling 10 amps by Fenix, but has been measured by CPF members to pull 11 amps on turbo; on paper, those batteries are not powerful enough to power the TK70 on turbo. Perhaps the AccuEvolution are overrated, but the numbers still don't add up for the Centura unless they are underrated, which is doubtful as the rule of thumb for LSD NiMh is (max. discharge rate = ~battery capacity). If anyone has been able to use the centuras or any LSD batteries for more than a couple of weeks in their TK70 and use turbo regularly I'm definitely interested to hear about it.

I also tried with 4 Tenergy Premiums (non LSD), rated at a max discharge rate of 47.5 amps. and those work just fine to this day. The rule of thumb for non-LSD batteries is (max discharge rate = ~ 5X battery capacity) In theory, any high capacity non-LSD NiMh D cells should be fine in the TK70 on turbo, but capacity will dictate the max runtime.

Allright, back to the topic at hand; I'm just trying to save people from expensive bad experiences.

It's funny because I get slightly different results with LSD Nimh with the TK70 on turbo. 1h17 mn max with the LSD and 1h31mn max with non LSD. I did a few tests with the LSD and got consistent results (~1h15mn on turbo)
LSD 8000 mAh from Enix brand. Non LSD 10000 mAh white label from Tenergy.
 
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StorminMatt

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I should also say that I have NEVER heard that LSD batteries are unsuitable for high current. In fact, it is generally accepted that Eneloops are better for high current than other, non-LSD mainstream NiMH AA batteries (this wouldn't include high drain batteries like Elites). My recommendation would be to at least try using a LSD NiMH D like the Tenergy Centura before saying it WON'T work.
 
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