Fenix TK40 on 4AA....

[pseudoblue]

2. Is the MC-E wired parallel or in series?

They are driven in series.

...Slightly less than half. You can get around 1 hour runtime with 4 good quality AA batteries. I wouldn't recommend running 4xAA alkaline at turbo mode.

i think 4aa would be fine and safe for any level but turbo " you can use turbo but i wouldnt do it for to long" but that just my opinion

To add, yeah, it's probably because with 4 alkalines on Turbo, they cannot hold 2.3A - 3.0A very well once they drop to a certain voltage (links given by LEDNinja were very useful). Older alkalines for example, will tend to leak almost immediately. Some newer alkalines may hold up until the light dims, and will need replacements immediately. I may think majority of consumers falls under the category of storing alkalines too long and are still in their packages. It's probably best to run at Low and Medium in any emergencies.
NiMHs are recommended if you want to run with 4AAs on Turbo. Since Eneloops are recognized, so it's good to use them. I am using 8x Imedions for my TK40 btw.

 

[csshih]

I'd also like to hear from more dealers or Fenix itself. Myself and plenty of others haven't had a problem with their lights and I use mine often, although with Eneloops.

fact: this is the most returned light due to consumers making mistakes, batteries leaking, etc.

is that enough, or do you have to hear it direct?

 

[pseudoblue]

...
If one were to use NiMH cells right away, would one be best with high capacity or low self discharge, due to lower internal resistance?

I think either is fine. The thing is with high capacity nimh (2500-2700) it's prefered that all 8 batteries are of the same age. You may have 2 different sets(of 4) that is 2 years older, but they retained their charge differently after prolong used together, one set appears to have a higher resistance, may become a problem in the TK40 setting. Something to think about.
Same for LSD batteries too, but it may not be an issue...

 

[defloyd77]

I think either is fine. The thing is with high capacity nimh (2500-2700) it's prefered that all 8 batteries are of the same age. You may have 2 different sets(of 4) that is 2 years older, but they retained their charge differently after prolong used together, one set appears to have a higher resistance, may become a problem in the TK40 setting. Something to think about.
Same for LSD batteries too, but it may not be an issue...

Thanks. If I were to get one of these, I'd definately get 8 new NiMH's and mark them somehow and use them exclusively on the TK40.

 

[jirik_cz]

They are driven in series.

That is interesting info. How do you know?

fact: this is the most returned light due to consumers making mistakes, batteries leaking, etc.

is that enough, or do you have to hear it direct?

I would recommend asking other dealers about return rate of TK40. I asked our local dealer and they already sold tons of TK40 (much more than other MC-E/P7 lights running on lithiums) and the return rate is very small.

 

[pseudoblue]

That is interesting info. How do you know?

In the Cree's MCE datasheet mentioned flux readings with 4 LEDs driven in series.

 

[jirik_cz]

In the Cree's MCE datasheet mentioned flux readings with 4 LEDs driven in series.

Well, the dies of MC-E are individually addressable. You can wire them in series, parallel, serio-parallel...

Cree defines the light flux at some given conditions, but that doesn't tell us anything about the actual wiring of the LED in the flashlight.

I thought you have some better sources

 

[ubetit]

fact: this is the most returned light due to consumers making mistakes, batteries leaking, etc.

is that enough, or do you have to hear it direct?

Presented in that form it is hearsay evidence, not fact.

Again folks, i'm not saying that issues with the TK40 don't exist, it may be the worst design in the history of flashlights. The problem so far is that one dealer had a comment with no details on the rates of return and the reasons for return in quantifiable numbers. Just for giggles, it may be that 4sevens received a bad batch so his experience is different from other dealers.

My theory is that the problems with the TK40 are mainly due to inserting the batteries incorrectly. This is something I can't prove without data.

 

[pseudoblue]

Well, the dies of MC-E are individually addressable. You can wire them in series, parallel, serio-parallel...

Cree defines the light flux at some given conditions, but that doesn't tell us anything about the actual wiring of the LED in the flashlight.

I thought you have some better sources

Hrm, as I understand it, unless someone can clarify this point for us. At Turbo, it's drawing about 2.3 - 2.6A with nimh. Each LED can't possibly take that much if it's in parallel @ around 5.2 - 5.6v.

 

[jirik_cz]

Hrm, as I understand it, unless someone can clarify this point for us. At Turbo, it's drawing about 2.3 - 2.6A with nimh. Each LED can't possibly take that much if it's in parallel @ around 5.2 - 5.6v.

The light is not direct driven. There is a driver Current draw will tell you nothing about wiring of the LED.

 

[collo]

I did a test last night using 4 * Eneloops on turbo.

Was not concerned about the head overheating, but relied on the over-temperature protection to kick in if required, which did not happen.

Evey 10 minitues, removed the battery carrier and felt if the batteries were getting hot.

All fine up to the half hour mark - the head was warm, but not so hot that you couldn't hold it. The batteries were fine.

At about 40 minutes, there was a single quick dip in the output, but then the output looked the same.

At 45 minutes, checked the batteries and they were quite hot.

I would say that once the voltage of the batteries starts to drop steeply, the driver pulls increasingly larger current causing the heating.

The torch presumably would cut out when the voltage gets low enough, but since it's designed for 8 cells on turbo, the cutoff limit would be too low to limit the current on 4 cells to a safe value.

I like the reduction in weight when using 4 cells, and bought the light for the high output. Based on this quick test, I would say half an hour is a good limit for 4 Eneloops on turbo.

 

[coldpointcrossing]

What about 4 lithiums? I've seen the dealer sites state alkalines and NiMH are ok but nothing of lithiums. I understand that lithiums carry a higher voltage and may blow a TK40 with a full carrier, but what if you used 4 in a pinch?

 

[flasherByNight]

all I have to say as far as 4sevens comment about them never carrying an 8AA flashlight again is one thing....

BUT has ANYONE seen a single thread here on CPF about a TK40 blowing up due to this?
Continually repeating this in threads where it's not directly relevant is trolling imo

Not to refute 4sevens experience, but again I think you have to be an idiot to install the batteries improperly.

 

[Link Archer VI]

Not exploding lithiums, but someone here did have alkalines leak in their TK40. There was a thread about it posted a few months ago. Let me see if I can find it... Ah! Here it is: https://www.candlepowerforums.com/threads/235983
And I just remembered someone else did load lithums incorrectly and the batteries got really hot! The thread is here: https://www.candlepowerforums.com/posts/2908296#post2908296

 

[coldpointcrossing]

I'm not sure if the following was in response to my question -

BUT has ANYONE seen a single thread here on CPF about a TK40 blowing up due to this?
Continually repeating this in threads where it's not directly relevant is trolling imo

If so, my question about using 4 lithiums in a pinch and if that could blow a TK40 was not meant "to explode", but rather cause damage to the electronics and LED's. If I wasn't clear enough and my comment too easily misconstrued then my mistake.

 

[coldpointcrossing]

https://www.candlepowerforums.com/posts/2908296#post2908296

Just used the shortcut. Thanks for posting!

 

[headophile]

i definitely think the problems associated with this light stem from user error or incapable cells

 

[mikekoz]

I see no reason for using 4 cells in this light. Why would one want to use the TK40 with half the runtime? That is one of the best features of this light! It does make it lighter, but what are we......(As Arnold would say)girlie-men!!!!!! . As far as the problem of using 8 AA batteries, there is no problem. Just put the cells in correctly...like any light, whether it uses AA, AAA, 18650, CR123, etc. Plus AA NIMH batteries are a lot safer than lithium ion cells anyway. Just my 2 cents!

 

[headophile]

I see no reason for using 4 cells in this light. Why would one want to use the TK40 with half the runtime? That is one of the best features of this light! It does make it lighter, but what are we......(As Arnold would say)girlie-men!!!!!! . As far as the problem of using 8 AA batteries, there is no problem. Just put the cells in correctly...like any light, whether it uses AA, AAA, 18650, CR123, etc. Plus AA NIMH batteries are a lot safer than lithium ion cells anyway. Just my 2 cents!

i think the weight factor is an important consideration if one needs to use this light for an extended amount of time. in such a scenario, i'd rather have 4 cells in use and have 8 or even 12 in my bag or pocket as backups. this light is not too heavy by any means but i'm thinking if you have to use it for, say, 5 hours straight you'd start to feel the weight a bit on your hand.

the tk40 is very light with only 4 cells in