A very quick question about TK40

Hi folks!

Im currently using ordinary alkalines in my TK40. To those other owners who use NiMH batteries of any brand - is there to "the eye" some advantage in the light output? Does rechargable batteries have any advantage against alkalines in the TK40 (except for that they can be recharged or course)?

And, yes. I have used the search function and read some threads for an answer but I cant really find a correct/full one.

So... whats your impression on the "eye value" of the light comparison between alkalines and rechargables in the TK40?

I cant answer your question but I think that if there was an increase in output with NiMH batteries you eyes would not notice because it will would only be a small difference.

Thanx for the answer, Bubu. It would make sense in my mind too when reading the "data-numbers" in other threads about this issue. If any one have actually seen any increase in "eye-light" and with what brand - plz do tell.

A few things about the alkalines... Any type, mind you, will suffer from voltage drop under any large load. Basically, the internal resistance of each cell may cause the voltage to drop too low for the driver to access turbo output.
Also, the TK40 has a rather large "parasitic drain." Basically the electronics of the light continue to pull a minute amount of power, even when the light is off. This parasitic drain can cause the alkalines to leak as happened to one member here. It ruined the light.

A decent charger and a set of primary and backup rechargeables won't cost that much, maybe an additional $50 on the purchase price, but spending an extra $50 now, can save a huge headache later when the alkalines (eventually) leak, ruining your light. Plus, you already have a charger and batteries ready to go for any other lights you purchase.

John_Galt said:

A few things about the alkalines... Any type, mind you, will suffer from voltage drop under any large load. Basically, the internal resistance of each cell may cause the voltage to drop too low for the driver to access turbo output.
Also, the TK40 has a rather large "parasitic drain." Basically the electronics of the light continue to pull a minute amount of power, even when the light is off. This parasitic drain can cause the alkalines to leak as happened to one member here. It ruined the light.

A decent charger and a set of primary and backup rechargeables won't cost that much, maybe an additional $50 on the purchase price, but spending an extra $50 now, can save a huge headache later when the alkalines (eventually) leak, ruining your light. Plus, you already have a charger and batteries ready to go for any other lights you purchase.

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large drain? everything i read says it will take almost a year to kill the flashlight from the drain, you have a link?

Hi, John!

Wasnt the drain solved by turning the bezel 2,5 rounds - disconnecting it from the "connection-drain"? (which I always do when I leave it off for 2-3 days).

LittleBill said:

large drain? everything i read says it will take almost a year to kill the flashlight from the drain, you have a link?

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What I meant is that is is a rather large drain, all things considered. Enough, apparently to cause the batteries to leak in this guys light. https://www.candlepowerforums.com/threads/235983&highlight=TK40+battery+leak

Alkalines and expensive, high drain devices do not mix, as can often be seen. Especially when quality rechargable Ni-MH batteries and good quality chargers don't cost a whole lot, and can in fact, save you a lot of pain and cash in the long run.

John:

I see what you mean now. Still being a layman when it comes to these things.. thanx for the info. Yea, it sure is a financial and functional deal to buy those rechargebles and a nice charger for my TK40.

I have not put alkalines in my TK40 (and would not except for short periods if I had no alternative) but I have run it on lithium primaries and also eneloop NiMH rechargeables, and the light output seems about the same.

I would definitely recommend running with NiMH and only have primaries as an emergency backup plan, and if running alkalines run 4 at a time, don't use turbo, and lock the light out when not in use. An alkaline battery leak in your nice TK40 will definitely ruin your day!

In all cases, make sure all the cells used are well matched - in the case of primaries they should all be new from the same age batch and manufacturer, in the case of NiMH they should be either new or run together the same number of charge/discharge cycles. And it goes without saying they should all be the same type and manufacturer.

and pay close attention to polarity when loading!

Thanx, jahxman, for that extra info

NiMH last a lot longer.

Magic Matt said:

NiMH last a lot longer.

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Is there any difference to NiMH and eneloop or is it just a different "brand" so to speak within the same category?

Eneloops belong to a special class of NiMH known as LSD, or Low Self Discharge. NiMH lose their charge rather quickly, even when not being used in a device, which is the only downside to a very useful battery chemistry.

LSD fixes that downside, allowing NiMH to sit idle for a very long time without losing charge. They have slightly smaller battery capacity than non-LSD but they are otherwise so excellent that most will now recommend them for just about anything.

Eneloop is a specific brand (from Sanyo) of LSD that happens to be superb and trusted.

Thanx, carott, for that info! Cause I just ordered some for my TK40

When I first got my Fenix TK40 I experimented with using Duracell alkaline batteries for a week or two. I wanted to see if I would gain anything with the Eneloop batteries that every other TK40 owner swore by in the online reviews that I read before I bought mine. After messing with the alkalines I bit the bullet and I bought Sanyo Eneloop AAs.

I never went back to alkalines in my TK40.

Yes there is a big, noticeable difference between alkalines and Eneloop batteries in the TK40. With alkalines there isn't a huge difference in light output when going from high mode to turbo mode. With Eneloops, that jump to turbo is a big leap. Yes, you will notice the difference or at least I did with my eyes.

Note that if you only use your TK40 on high, medium, or low and you never use the turbo setting, then you may get by just fine with alkaline batteries. But honestly, the whole reason to get a TK40 is because of its beautiful beam pattern and light output with the turbo mode and that's what you pay for. The only way to see the full potential of the TK40 is with it powered by Eneloop batteries.

Those are just the performance benefits of Eneloop batteries. Once you factor in the fact that, unlike alkaline batteries, they do not leak whatsoever, there really is only one way to go - get the Eneloops. :thumbsup:

There are two really good reasons to use NiMH -- first, they are rechargeable, so once you get past the initial investment you are running your light for nearly free. And second, NiMH is a hardier battery chemistry -- where alkalines will suffer from voltage sag under load (forcing the regulator to work harder, and becoming more inefficient), NiMH will not sag as much, allowing a light to be driven harder for longer.

Thanx, Locoboy5150, for that comment! And that is , as you say , "the big thing"... the highest perfomance possible on the highest level! I mean... it shines "pretty" good right now on highest but... cant wait until I load it with Eneloops and with all the other advantages those come with hehe

carrot: great info for a layman trying to get into this "battery-chaos"

If you liked that explanation, you will like other things I have written on the subject of flashlights, linked in my signature.

John_Galt said:

What I meant is that is is a rather large drain, all things considered. Enough, apparently to cause the batteries to leak in this guys light. https://www.candlepowerforums.com/threads/235983&highlight=TK40+battery+leak

Alkalines and expensive, high drain devices do not mix, as can often be seen. Especially when quality rechargable Ni-MH batteries and good quality chargers don't cost a whole lot, and can in fact, save you a lot of pain and cash in the long run.

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to be honest nothing in that posts points to anything about a large parasitic drain,

the issue with his light was the batterys exploded due to alkalines, which is by no fault of the flashlight.

for me to lock requires the head to almost come off.

we shall see how long it really takes to kill the light, mine have been in over 2 weeks with 0 issue using eneloops of course

The_Viking said:

Is there any difference to NiMH and eneloop or is it just a different "brand" so to speak within the same category?

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Eneloops last no way near as long as my regular NiMH, but they stay charged for longer, which is probably more sensible in a flashlight you may not use daily.

By way of comparison, I get about 700 shots out of 4 Duracell high capacity NiMH cells, and only about 500 from the Eneloops... however I leave Eneloops in the camera bag because I know they'll stay charged.