TK40 Battery Problems?

I've been looking at getting myself a TK40 recently, and while i have lots of eneloop/duraloop batteries i was wondering if the small differences in capacity between cells, some having been used more than others, would cause any problems in such a multi-cell light?

It is this worry that is putting me off, as i had thought that if some had been cyled 5 or 6 times compared to others only once or twice, then some may have slightly higher capacities than others even if they are all eneloops. If i then ran the batteries right down then couldnt this cause technical problems as some would be flat before others and current would be drawn at different rates? :shrug:

Im definately not any sort of expert on the technical problems involved so any help would be great.

Thanks

How much difference?
All batteries are not alike and even among same batch there's difference.

I wouldn't worry too much. Although I would make sure that the new set and the set used more each span across the full 4.8 v if you understand what i mean. It's OK to put new batteries in parallel with old ones (fresh from the charger) but putting them in series isn't - at least if their capacity vary too much.
Even amongst a new set I believe I've seem a difference of 100 mAh from the best to the weakest (AA LSD). So if it's not more then don't worry too much about.

ill avoid this light forever simply because 8 cells leaves too much room for problems (incorrect insertion in holder and difference in charge state)

single cell lights ftmfw.

waddup said:

ill avoid this light forever simply because 8 cells leaves too much room for problems (incorrect insertion in holder and difference in charge state)

single cell lights ftmfw.

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Not a problem if you focus on your loading and use a dedicated set of Batt's for your light.

To the OP just discharge all the cells to about the same level using another aa device, then charge the cells together and use them together. Small differences won't be dangerous or cause performance problems, especially with NiMh.

If possible charge them as a pack. I got a 8aa series battery holder at Radio Shack for 2 bucks and use this and a smart charger to charge all cells at once.

After a few cycles they will be balanced, just get em pretty well discharged before your first group charge and you'll have a good start.

I haven't had any of these problems with my TK40 but then again the batteries that I use in it are all fairly new. I also pay attention to the polarity when loading batteries into anything, including my lights. I honestly cannot recall the last time that I loaded batteries in anything incorrectly.

I'd suggest waiting until the TK45 comes out then pick either that or the TK40. People have been complaining about the 8 AA power source ever since the TK40 came out. Let them stew and just get one (or the TK45) and enjoy it.

That's what I did. Instead of complaining I bought one..and was blown away by its quality. :twothumbs

i charge 4 eneloop at a time in a 15 minute charger for varied times, to full of course, no issues.....and have u seen the batt cartridge....if U load the + side against the spring, i feel sorry for u. the tk40 is so simple, and worth every penny.

PBX

PolarBearX said:

i charge 4 eneloop at a time in a 15 minute charger for varied times, to full of course, no issues.....and have u seen the batt cartridge....if U load the + side against the spring, i feel sorry for u. the tk40 is so simple, and worth every penny.

PBX

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If you charge eneloops (2000 mAh) in 15 minutes, that's 8 amps through the poor things. It might be slightly bad to run 8 AAs in a group, but it won't significantly hurt them - just be careful when you're loading them and it ought to behave nicely. And I do hear that the TK40 is a great light...

yep I live on the edge lol, and my lights better keep up...thats why i mentioned it tho, cuz the eneloop and tk40 can take it....plus I hate waiting for a long charge with every bone in my body.

PBX

Eneloops are pretty resilient and not terribly finicky. If the difference is only 5-6 cycles on some and 1-2 on others, you don't have anything to worry about. If however any of those cells have been severely discharged (to the point of internal damage), then you might be in trouble and should discard the damaged cells.

I think the two biggest mistakes people frequently make with rechargeable cells is over discharge, and inter mixing. Cells should never be over discharged EVER. In the case of flashlights that means discharging them past the point of dimming. Carry backups, if you need to. But do not excessively discharge the cells. Cells should never be inter-mixed (especially cells in series). If one cell is discharged more than the others do NOT mix it in with fully charged cells.

Vent, fire and explosion reports on CPF almost always result from either or both of the above user mistakes. Flashlight vent/fire incidents without either of the above conditions are very rare. Flashlights do not just spontaneously explode without provocation. (I am going out on a limb with that last statement... so perhaps an IMHO is needed)

kramer5150 "In the case of flashlights that means discharging them past the point of dimming."

What about unregulated lights. Don't they normally dim as the voltage drops. Also I have a TK40 and charge the batteries once turbo mode cannot be maintained. Is that the way to go?

Jash said:

kramer5150 "In the case of flashlights that means discharging them past the point of dimming."

What about unregulated lights. Don't they normally dim as the voltage drops.

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I have found direct driven eneloop setups to diminish very slowly, and behave more like regulated circuits in bigchelis' sphere. DD-18650 lights also exhibit a very gradual drop off, at least with the sanyo 18650 cells I use. But once the cell dumps, its a slight but noticeable drop in output... at least I find that to be the case.

The best advice I can give is to always play it conservative (especially with Lithium-Ion), and leave yourself some buffer and room for error. I run my Malkoff M60 with an 18650. At that voltage it draws .81A. My cells are around ~2200 mah (reading off my hobby charger). From there run time is 2.2 / .81 = 2.70 Hours per cell. I give myself a 2 hour window for each cell and keep mental tabs on how much I have used the cell. Sometimes I forget after a few days and just play it safe and replace/recharge the cell.

Its pretty well documented that eneloops are ~1950 mah, so you don't even need a hobby charger to do this.

Hope this helps... and OP, I really do think you are OK with the TK40 + eneloop setup, just avoid over discharge and inter-mixing. Carrying topped off backup cells is the easiest way to avoid these conditions.

Good Luck!!

I have some questions on TK40 battery and charger configuration for two situations: greenfield and existing set up.

Greenfield: User has no AA rechargeables and no AA chargers. How many Eneloops (probably 8, unlikely 16) and what specific charger should they get - to be used only for TK40.

Existing: User has a mixed bag of a few dozen AA's mostly used for other flashlights, radios, CD player, portable speakers, whatever - in varied rotation around home. Has maha c9000 and maha fs401 - often in use. To suppport TK40 should a new set (8) of Eneloops be purchased? Or will more dedicated be more practical? Will those charger suffice? (I would think so) I know this is a more it depends kind of question, but mainly looking for any learnings of a TK40 user.

I was concerned like you about using and maintaining a 8 cell light until I got the TK40.

I've had no battery problems. I exclusively use eneloops. I have a 'eneloop' 4 cell charger (not fast- not 15 minutes).
It's my understanding that because the light can operate on 4 cells in an emergency it's not absolutely critical that each bank of 4 must be at the exact same level. That said, I always charge all 8 cells at the same time, four at a time, and always re-insert them in the holder in the same ''bank''
* the battery holder could be better looked at as having two sets of four banks (slots).

Not sure I've helped but.... to answer the original posters question don't worry about it. I have marked with a sharpie all my ''4 sets''. I just keep the TK40 set together.

Hope that helped

ps ... if you have ''lots of eneloops/duraloops' then this really is the light for you. I love mine.

noisebeam said:

Greenfield: User has no AA rechargeables and no AA chargers. How many Eneloops (probably 8, unlikely 16) and what specific charger should they get - to be used only for TK40.

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The above Greenfield situation was what I was in when I bought my TK40 last October 2009. I used it with the eight free alkaline AA cells that the dealer threw in for about a week or two just to see if I could tell the difference when I got eight new Eneloop batteries. I *immediately* could tell the difference between the two types of batteries, especially when using turbo mode.

As for the charger, I nearly caused a riot over in the Flashlight Electronics forum because of my recommendation to someone else based on what I bought. I honestly don't care really because I love what I bought and I stand by it so I'll mention it here too. I bought the Titanium Innovations M-8800:

http://www.batteryjunction.com/8800.html

Others jumped on me over there because I said it was good and that I liked it. People wanted to quantify how good it was because they had similar information on other chargers, some that cost a lot more than mine. Whatever. All I can say now is what I said then. It just works and it works great for me. I have no scientific data to back up my battery charger choice other than the following:

Does it work well - yes.

Do you like it - yes.

Are you happy with your purchase - yes.

Here's that other thread to give you an idea how technical this subject can become:

https://www.candlepowerforums.com/threads/258486

So there you go. That's the battery and charger set up that I bought right after I bought my Fenix TK40. I did not know how dedicated people are to their battery chargers and how technical they are when they purchase one. I had no idea that flashlight guys were as dedicated to the subject as us R/C guys. (The Tekin BC112A and BC112C are all that I use for my R/C battery packs.)

Honestly, if you have trouble inserting AA batts into the tk40 battery holder properly ... there's a much bigger issue at hand. It is very, very clear the first time you see the holder. It's not like there's any real room for confusion.

If you have troubles having 8 dedicated Eneloops etc ... for your tk40 - then, again, there are serious concerns non-flashlight related at work here.

If there are any lingering issues over the above two mentioned points ... then a suggestion for a mag 3D would be more appropriate.

If a person has reservations driving ... they should take public transit and let someone else drive for them. Simple as that.

I'm not speaking to anyone specifically here ... i'm just saying that given this is a 100 dollar + light ... there should be at least 100 dollars worth of brains to accompany it ... not a 5 cent brain. If problems arise, then shine the light at the user instead of the product.