Hot batteries in Fenix TK40

[jahxman]

Hot Batteries! Yowch!

So I got my TK40 today, and right away loaded it up with Energizer Ultimate Lithiums ( I dont have a recharge setup yet for AAs) and played with it for a while. Overall, I am pleased with the light.

Then, I put it away, unscrewing the end cap 2.5 turns as the little instruction manual says to eliminate slow battery drain...Can't say I was all that happy having to do that, but ok.

I put my hand on it about 40 minutes later and it was just about hot enough to cook something on! I immediately took out the batteries, and some of the lithium batteries swelled a bit, to the point that their outer foil/plastic jackets no longer touched at the seam.

What is going on? Did I do something wrong? I am admittedly a bit of a newb here but I've been lurking at CPF for a while and decided to try this light out.

Anyone have any ideas what's going on?

 

[qip]

ok that does worry me a bit , considering the L91 is my favorite battery that i was gonna have this puppy run on , and all the stories i read on primaries exploding and with the tk40 using 8 of them well

 

[jirik_cz]

What was the condition of the cells. Were they brand new or not?

 

[EngrPaul]

Sounds like you exchanged slow battery drain for fast battery drain.

Sorry to hear that! :mecry:

 

[DeadLed]

Do you have a way of measuring your L91´s? I use Eneloops in my TK40 and no issues. We need to get to the bottom of this.

 

[AusKipper]

And all the batteries where definitely in the correct way around???

 

[jahxman]

OK - I may have jumped the gun on this.

First of all, the batteries were all brand new, out of the same 8-pack.

After this happened I put alkalines in, played with it with the alkalines, and then tried the unscrew end cap test and left it for an hour. No problems.

I examined the lithiums I had in it before, and realized that they didn't swell up - they just got hot enough to shrink their plastic/foil jackets a little. And only three of them looked like this - the other 5 looked normal.

I put the Lithiums back in, taking extra care of the polarity - I thought I had had it right the first time; I am a pretty detail oriented person and battery polarity is just basic. However when I took them out before they were very hot and I was more focused on getting them out than checking the polarity.

SO I tested the light with the lithiums back in for a while, all seems normal (and turbo mode seems a good deal brighter with lithiums then with alkalines)

I untwisted the end cap until the light would no longer come on, just as I had done before, and put it down for a while. It has been almost 2 hours now and the light is cool to the touch, tests fine, and when I check the batteries they are cool as well.

So, I think this one was user error - I must have gotten the polarity wrong when I put them in first time, and maybe the light was mainly running on the four that had the right polarity.

With 8 of these little suckers, I guess extra care needs to be taken with polarity, especially if using lithiums. Or you just have to not be a bonehead like me

 

[Burgess]

_

 

[StarHalo]

Something somewhere shorted..

 

[Haz]

How is the battery carrier and the contact with the interior of the light?. Any incorrect alignment?, I wonder if that is the place causing the shorting.

 

[Mike89]

Something somewhere shorted..

That's what that sounds like to me, or incorrect battery placement. I have regular alkalines in mine. When it's off, it's off.

 

[Glock27]

I had a hot battery event in my TK40 last night also.
I ran a set of Sanyo 2700s for a while and then changed out to a second set of Sanyos. All cells are new and were purchased for the TK40. I can't remember whether I had it on low or off, but when I went to pick it up a couple minutes after changing batteries, the tube felt warm. I immediately took out the carrier and the cells were very hot. I did not think any cells were installed incorrectly. I see no signs of a short.
After cooling, 5 of the 8 cells accepted ~840 mAh. 3 took substantially more....~1200 mAh.
Cells from the "event" set are in light now and have not heated up even on turbo.

Does any of the above point to anything but goofing cell polarity on a pair?
What could effect 3 of 8 cells?
One thing I did notice is that one of the 4 Negative contact "fingers" was not bent to the same level as the other 3.
Looks like a good idea to order a spare carrier. I don't think a loaded carrier would survive a 3 foot drop test.
G27

 

[MichaelW]

Has anyone done this comparison:
8 x AA alkaline against 4xAA L91 lithium.

 

[Glock27]

I've changed out several sets of cells since I had a pack get hot the other night.
A close inspection of the carrier, tube and all contacts revealed no shorting of any kind. Therefore evidence strongly points to me having one cell in backwards.
Could someone confirm one cell reversed in a 4s pack would cause the heat to rise?

Fortunately, the Sanyo 2700s that got hot have given a consistent 2 hours and 20 minutes on 2 cycles of Turbo....so I don't think they're hurt.
G27

 

[Bullzeyebill]

Well, today is the 8th and I am sure that those having problems with their TK40's have done the right thing and contacted the seller by now. What did they say? This problem sounds sort of dangerous, so the seller should know about it, if not the manufacturer, and maybe production/sales should stop till this is worked out.

Bill

 

[Glock27]

I have heard of no problems with the light....It is not the lights fault that a battery was probably inserted backwards. I have had no further events and have used my light every night this week.....depleting at least 1 set of 2700's a day...sometimes 2.
I think the TK40 is a great light.
G27

 

[jahxman]

contacted the seller by now. What did they say?

I wrote fenix-store.com, where I got the light, and the response was:

Jim,
This may have been an isolated incident. How are the batteries oriented inside the light? There may be some confusion as the diagram in the instructions shows all cells positive side towards the front. In reality the cells should always be installed with the negative end towards the springs. Can you confirm this?

Regards,
Trevor


I have been using the light daily, and same as Glock27 I have had no further heating events. It is possible that we both managed to reverse polarity on a cell, as unlikely as it seems to someone experienced with putting batteries in devices - but there are 8 of them in this one.

I like the light a lot, I think others will as well - so, unless it happens again I think it was my own error. I continue to check the light 30 minutes after putting it away on lockout, just to be sure.

 

[f22shift]

they should consider making a carrier with a built in port. sell with a charger.
like a fm style carrier.
this can reduce user error with less loading.

 

[TedTheLed]

the battery install instructions that come with the tk40 are confusing - Trevor tried to correct the TK40 diagram by saying 'all batteries should be installed with negative ends towards springs..' but this can be confusing also because it could mean either the spring in the end cap, or the spring sticking out of the forward end of the battery carrier, doing either would be wrong: the 'spring' the negative battery terminals should 'face' ie. contact, are the springS INSIDE the battery carrier. duh right? well I did it wrong the first time --
(hey they do things differently in China, right?)
...works fine now.

 

[Mike89]

the battery install instructions that come with the tk40 are confusing

Don't know how much clearer the instructions could be dude. Almost sounds like you've never installed batteries before if you didn't know the springs would make contact with the negative end. Dunno man, it was pretty clear cut to me.