TK40 and Eneloops question

Up until recently I have been using Duracell Alkalines in my TK40 and they work well. I have been researching info on the best batteries for the TK40 and nearly every response in the forum indicate that Eneloops are by far the best to use.

I went out and purchased 16 Eneloops, put them through a recharge cycle to make sure they were all at the same voltage level. I then measured the voltage of each and they were all indeed at the same voltage.

So out came the Alkalines, in went the Eneloops, on went the TK40, big burst of light, a few flashes, and no light!

I checked to make sure the batteries were in the correct direction and all was OK. I checked everything was nice and tight and all was OK.

Just no light!

I put in the Alkalines and still no light.

I sat there and pondered this slight catastrophe. After a few minutes I thought I'd click the TK40 button just one more time before I put up the R.I.P. sign, and LIGHT!

I turned it off/on a few times and it flickered on and off a few times, but after a while it came back to life.

I flicked through the modes, tried the beacon, the blinking, the strobe and all was OK.

Not sure what the blazes happened, but all seems OK on Alkalines now, high mode is just as high as ever, and I'm VERY reluctant to try the Eneloops again.

Just thought I'd share my scare with you and ask if anybody might have an idea what might be the problem.

Looks like the Polestar will get the next try-out with the Eneloops before I risk my pride-and-joy again.

Regards,
bedazzLED.

The Eneloops should pose no risk as they're lower voltage than the alkalines.

It would be worth cleaning the all the contacts....
- battery carrier, both the battery side and the ends
- the head unit.
- ends of batteries
A pencil eraser makes for a good mild cleaner. Some iso-propyl alcohol can remove any grease etc that has found its way from the threads to the contacts. (available from chemist shop)

You may also want to re-seat the switch and clean its mounting surfaces.

My nine months old TK40 has never showed any difference in behaviour between alkalines and Eneloops. :thinking:

I guess that the reason behind your trouble is a bad/uncertain contact between one of the various springs of the battery holder and their interfaces in the body of the light. If I were you I would clean and check all the internal contacts and springs.
Besides it is unlikely that you can damage your Fenix just by using NiMH's.

Thanks for all the suggestions and advice.

I've just finished cleaning all the contacts, reseated the switch, tightened and checked everything.

Put the Eneloops back in and still no light.

I gave it a little 'percussive maintenance' around the head in frustration and all of a sudden it turned on!.

I've switched it off/on a number of times and it seems to be OK. I then left it on high for a while and after about 10 minutes it just switched off. I banged it around the head again and it switched on again.

Looks like something is loose somewhere.

One possibility is poor contact (bad soldering point, something is loose or something is dirty) at a point where tiny size differences in batteries actually makes a difference. "Percussive maintenance" (I love that word) makes everything snap back in place and restore contact. You have indications that this happens with eneloops, so I would suspect the battery carrier or somewhere that the carrier connects to. Measuring the exact dimensions of the alkaline and eneloop may give you a hint of where to look.

Trying to chase down exactly WHERE the poor contact is located can be very tricky and time consuming. It's no big deal if you can clean away some gunk to restore contact, but finding a bad solder point or otherwise broken / partly broken connection is another story. Even if you find it, fixing it requires some skill and would most likely void the guarantee.

I would focus on the carrier: Scrutinize all contact points between batteries and holder, all wires/connections and the connection points between holder and flashlight. Clean it again. If nothing improves, contact your dealer for a replacement because this clearly is not how it's supposed to be. Others use the TK40 with eneloop and absolutely no problems.

I don't know if this is helpful, but as I was taught, use a pencil eraser on the contacts. It always has worked for me? YMMV

Of all the Lights out there, the one I'll never use Alkalines is on the TK40, to much room for disaster, mine has work flawlessly with all kinds of LSD NiMH Eneloop Sony and the original Sanyo 2700,

If your lamp shuts down before the o-ring shows when unscrewing the back cap then thte top contacts in the magazine are maybe to flat. or dirty

good luck.

I've never ever had this problem either and I use Eneloops in my TK40 exclusively now. With my TK40 it never reached its full output potential in turbo mode with alkalines, only with the Eneloops.

I would try cleaning out the threads on the end cap and the end of the body tube. The grease that Fenix used on mine got "gunked up" pretty quickly.

Strange ... jankj has it nailed I think. Check out his comments.

I've been using Eneloops since day one ... hell, I bought this light based on AA usage like many people out there.

I've now tried cleaning, tightening, checking everything I possibly can and it is still playing up.

I can switch it on, let it tailstand for a few minutes and it will sometimes turn off. I can press the button and nothing happens. If I then apply a little more percussive maintenance either to the head or to the tail-end, sometimes it will turn on, and sometimes I have to press the switch again for it to turn on.

I think it's time to contact the dealer I purchased it from. Light is only 6 months old and has not seen hard times at all.

Sorry to go a little OT, but I've just received my TK40 today, put in some fully charged eneloops, and nothing happens :-( I've checked, double checked and triple checked I've got the batteries the right way round. The batteries show as ready in my Ansmann battery charger, so I think they're ok. Had the batteries in, out, unscrewed everything and put it back together, still nothing! Have I received a dud? Does this happen? Or am I just being a dullard?

Any advice much appreciated

Thanks

O NO! Lucky there's a warranty.

Jkbam said:

Sorry to go a little OT, but I've just received my TK40 today, put in some fully charged eneloops, and nothing happens :-( I've checked, double checked and triple checked I've got the batteries the right way round. The batteries show as ready in my Ansmann battery charger, so I think they're ok. Had the batteries in, out, unscrewed everything and put it back together, still nothing! Have I received a dud? Does this happen?

Click to expand...

Yes, duds happen. Fenix has a pretty good reputation, though, so if it was me, I'd go buy a cheap multimeter (in the US the cheap dial-based ones are about $9, I don't know about overseas). With the multimeter you can confirm that (a) the batteries are all working individually, and (b) when put into the pack, you get the full 4.8V (? I think the TK40 is 4 batteries in series?) out of the pack. If the pack is performing properly, then try reassembling the light, but leaving the switch off and manually performing it's function with a wire / paperclip / etc. (note: tongue not recommended :laughing. I don't own a TK40, so I'm not entirely sure this is possible--it depends on how the battery pack is designed. Alternately, you can use the resistance meter on the tailcap switch leads to see if the switch is allowing current to pass when clicked on.

If the batteries, battery pack, and switch are working, but you still don't get light, then I'd call it defective and send it back.

Hi Jkbam.

After trying the cleaning, tightening, re-seating the switch, ..., have you tried what finally worked on my TK40? "Percussive maintenance". A quick sharp hit to the head then see if it switches on. This certainly turns mine on but it turns off soon after.

Another suggestion I was told was to bend the contacts at the 'head' end of the battery carrier up a little because sometimes they don't make proper contact.

And don't worry too much Jash, the TK40 is still my all time favorite torch. I got in contact with the dealer I purchased if from and we was surprised to hear of the problems. He said he sells many many of these to LEO's and has had a total of 5 returned since it's release.

Mine is going back today and my replacement is already on its way.

I'm confident mine was just a flaky contact somewhere and is not common. I'm also impressed and filled with confidence at the durability of the TK40 by the Tk40 extreme torture thread:

https://www.candlepowerforums.com/threads/233856

One awesome test, don't know if I'd like to put mine to the test in that fashion.

Jkbam,

You can try checking to see if the switch is at fault by removing the tailcap completely, pressing down on the battery holder so that the 4 gold tabs and spring are making full contact with the head of the light, holding the battery holder in that pressed-down position, and then using a wire or paperclip to make a connection between the flat silver bottom of the battery holder (where the tail cap spring makes contact) and the threads of the body tube. If the light turns on when contact is made, then your switch is bad.

I did the above with my TK40 a couple of weeks ago when the switch was getting a little "flakey." I had to press it extremely hard to get it to turn on and off all of a sudden. After I did the above process, I determined that the tail cap switch needed some maintenance. I disassembled the switch and sprayed electrical contact cleaner in it and voila - it worked just as good as new again with just very light touches on the switch to get the light to operate.

Thanks for all the replies! I've tried the "percussive" and the paperclip, with no joy. I'll try and get a multimeter today, been meaning to buy one of those for a while anyway. I'll post back here with how I get on.

I am a bit dubious about this torch, I got it from Bestofferbuy in Hong Kong, and to me it looked as if the box had been opened, just little things like the instructions looked a bit crumpled. Don't really want to ship back, as I guess the cost of shipping is not going to be cheap and BOB don't refund return shipping according to their T&Cs.

Sometimes you do get duds, it happens.

I got a dud TK40 but it wasnt the same problem as you guys are having.

Details in this thread:

https://www.candlepowerforums.com/threads/250637

Jkbam, sounds like you dont have much choice and may have to ship it back to HK. That sucks. You often get it cheaper from HK and Ebay etc. but I rather pay a bit more and get it from somewhere more reputable.

I had a wrong light sent to me by a reputable store, I sent an e-mail complaining, the next day I had a reply and the correct item was already shipped out. They asked me to send the other item back and they were going to reimburse me for shipping or give me store credit. I ended up wanting to keep the 1st item they sent out so in true flashaholic style I ended up paying for the 1st (incorrect) item they sent out and the 2nd one I originally wanted, so I could keep both.

I'm having the same problem with my TK-40. If I have it on turbo it sometimes starts to flicker and then goes out. If I twist the head or tailcap a bit, it comes back on again. :thinking:

OK, if your TK40 didn't come on with the paper clip trick, then that rules out the tailcap switch as being the problem. The only other things left that I can think of are an electrical connection problem with the batteries or a problem with the head portion of the light.