Fenix TK75 Review including Extended Runtime Kits (2/4/6/8/10/12x18650 or 4/8xCR123)

[cheaperrooter]

Just got it. Be here in two days. B&H Photo for $169.99 free shipping (yes, the 2900 version)

 

[subwoofer]

Just got it. Be here in two days. B&H Photo for $169.99 free shipping (yes, the 2900 version)

B&H prices can be very good, they have even been good enough to get things shipped to the UK (photographic equipment rather than lights).

Hope you have a couple of sets of good quality 18650s charged and ready to go ;-)

 

[Lightning Bub]

Just got it. Be here in two days. B&H Photo for $169.99 free shipping (yes, the 2900 version)

I just ordered mine from B&H as well, along with two of their extended runtime kits (which they state include batteries, but I doubt it). I also picked up 12 3400mah 18650s and a nitecore charger from Amazon. All told, I am out about $300, but I have the bug now. I picked up a couple cheap lights recently, and now I am hooked.

Thanks for this awesome review!

 

[Lightning Bub]

The Fenix website and packaging for the runtime kits state "The use of more than three kits in one TK75 flashlight is not recommended", so I am confused as to whether or not they are considering the single tube that comes with the flashlight as a "kit".

 

[Lightning Bub]

Hello CPF!

I just got my TK75 today and I took it for a little walk. After a few minutes I noticed a little condensation(?) on the inside of the lens, near the middle. Is this normal for anyone else out there? The temperature tonight was about 5 degrees celsius. I can provide pictures if this does not make sense.

The actual light was mindblowing and the distance it covered was amazing! The only other light I have to compare it to was the SRT7 and it easily blew it out of the water. Not a fair comparison, but it was all I had to work with.
The weight was minimal. I could easily walk the dog and hold the light without any discomfort.

Hopefully the lens fogging up is not a big issue, but I had to ask.

Thanks in advance!

Mine gets a small condensation spot as well. It is right in the center of the lens and about the size of a dime. It shows up when the head is hot and goes away when it cools off. I am wondering how moisture could have gotten in there.

 

[subwoofer]

The Fenix website and packaging for the runtime kits state "The use of more than three kits in one TK75 flashlight is not recommended", so I am confused as to whether or not they are considering the single tube that comes with the flashlight as a "kit".

Having added two extensions (so having three battery holders in use), the tail-cap does not screw on as far. I would not want to add a third extension (fourth battery holder), so feel that their intention was to mean using no more than three battery holders (or the TK75 plus two extensions). IMHO.

Mine gets a small condensation spot as well. It is right in the center of the lens and about the size of a dime. It shows up when the head is hot and goes away when it cools off. I am wondering how moisture could have gotten in there.

The head is not sealed, so any moisture entering the batter tube (and being sealed inside when re-fitting the tail-cap), can make its way into the head by diffusion - just as with most lights.

 

[Lightning Bub]

Having added two extensions (so having three battery holders in use), the tail-cap does not screw on as far. I would not want to add a third extension (fourth battery holder), so feel that their intention was to mean using no more than three battery holders (or the TK75 plus two extensions). IMHO.


The head is not sealed, so any moisture entering the batter tube (and being sealed inside when re-fitting the tail-cap), can make its way into the head by diffusion - just as with most lights.

Thanks for the info. I went with two extension tubes and glad I did. I can get the tail cap to screw all the way down, but it is not easy and put a pretty decent rub ring on the inside of the tail cap.

Our weather has been a bit moist as of late. I will throw it in a box with a buch of dessicant packs to see if that removes the moisture.

 

[AA#5]

Does anyone know if the new TK75 uses a XM-L2 U2 or XM-L2 T6.

Also does it now have a lock-out facility?

The weather in London is sunny with a cool breeze.

The manual with mine says, "Unscrew the tailcap 1/2 turn or take out the battery to prevent accidental activation during storage or transport." After trying that, I found that the manual should have said, "Unscrew the tailcap TWO OR THREE TURNS."

 

[AbbyY]

Thanks a lot for review subwoofer!

Based on your runtime tests I've got it (L2 version/2.900 lumens) + 2 extender kits (12xNCR18650B Panasonic). It fits perfectly in my Niwalker BK-FA01/02 holsters:

And a comparison with SR95S UT, RC40 and SR96:

 

[NorthernStar]

Great review with nice pics!

Now i have a TK75-L2 incoming, and i have some questions about the light. It did not include any holster(like you mentioned) so i am going to carry it either in the pocket of my parkas or in my backpack. Since it has no lockout mode i wonder if accidental activation happens easy on this light? This question is subjective, but is it comfortable to carry the light with one extension kit attached to it over a longer time?

 

[blah9]

If I were you I would definitely lock the light out at the tailcap if it is in a backpack. I thought it would be okay to leave it on low mode and then turn it off to put it in a backpack since then if it did turn on it would only be in low mode. But then at an airport it turned on by itself in my bag and became very hot. It turned out that it even got switched into a higher mode. I could not easily touch the light because it was so hot, so I turned it off and unscrewed it with a buffer layer between my hands and the light. Be careful!

 

[AbbyY]

Is it ok to use unprotected cells? If I am not wrong, unprotected cells have a higher drain capacity and I think TK75 is suitable for using them. I have both protected and unprotected Panasonic NCR18650B rechargeables and I would like to use unprocteded ones too.

 

[NorthernStar]

If I were you I would definitely lock the light out at the tailcap if it is in a backpack. I thought it would be okay to leave it on low mode and then turn it off to put it in a backpack since then if it did turn on it would only be in low mode. But then at an airport it turned on by itself in my bag and became very hot. It turned out that it even got switched into a higher mode. I could not easily touch the light because it was so hot, so I turned it off and unscrewed it with a buffer layer between my hands and the light. Be careful!

Thank´s for the advice!

Well,then i will etiher lock it out by unscrewing the tailcap, or like mentioned earlier in the thread one can wrap a stick on velcro around the buttons to prevent accidental activation.

 

[Lightning Bub]

I use unprotected NCR18650B 3400 mah cells in mine (12 of them) and have had no issues.

Sent from my SCH-I605 using Tapatalk

 

[Visna]

Hi all,
are there any problems with switches like on tk41 ??? they looks similar

 

[AbbyY]

I use unprotected NCR18650B 3400 mah cells in mine (12 of them) and have had no issues.

Sent from my SCH-I605 using Tapatalk

Thanks! I also used unprotected 12xNCR18650B 3400 mAh and I've had no problem yet.

 

[gigahertz]

I have a question about the TK-75.

I want to buy an extension tube for my TK-75 and I am wondering if I should or have to use batteries of the same exact model/capacity for the extension tube.

Currently I am using the Fenix batteries that came with my TK-75 and would like to get some 3400mah Panasonic for the extension tube if it's ok to mix the two battery types.

Thanks!

 

[AbbyY]

You have to use the same capacity batteries and the same model/manufacturer. It is also strongly recommended that all batteries must be balanced (the same batch, the same number of charging/discharging cycles). These are condition for using batteries in multiple configuration.

 

[thedoc007]

I want to buy an extension tube for my TK-75 and I am wondering if I should or have to use batteries of the same exact model/capacity for the extension tube.

Currently I am using the Fenix batteries that came with my TK-75 and would like to get some 3400mah Panasonic for the extension tube if it's ok to mix the two battery types.

I know it stings, but as AbbyY said, you really should use batteries from same batch/capacity/manufacturer. Better to order a whole new set of 3400s when you order the extension tube (eight of them if you buy one tube). You can either keep the original four 2600s as spares, or sell them on CPFMP, or use them in other lights. Mixing cells is a bad idea - those warnings are there for a reason, and people have found out the hard way that lithium cells can fail spectacularly if they are mismatched. Learn from the mistakes of others, and stay safe!

 

[subwoofer]

I have a question about the TK-75.

I want to buy an extension tube for my TK-75 and I am wondering if I should or have to use batteries of the same exact model/capacity for the extension tube.

Currently I am using the Fenix batteries that came with my TK-75 and would like to get some 3400mah Panasonic for the extension tube if it's ok to mix the two battery types.

Thanks!

You have to use the same capacity batteries and the same model/manufacturer. It is also strongly recommended that all batteries must be balanced (the same batch, the same number of charging/discharging cycles). These are condition for using batteries in multiple configuration.

I know it stings, but as AbbyY said, you really should use batteries from same batch/capacity/manufacturer. Better to order a whole new set of 3400s when you order the extension tube (eight of them if you buy one tube). You can either keep the original four 2600s as spares, or sell them on CPFMP, or use them in other lights. Mixing cells is a bad idea - those warnings are there for a reason, and people have found out the hard way that lithium cells can fail spectacularly if they are mismatched. Learn from the mistakes of others, and stay safe!

I'm going to be controversial here and contradict the previous two posts.

The TK75's battery carrier uses 2S2P configuration which gives the 8.4V working voltage. If you add a second you still have 8.4V as the second carrier is also 2S2P, and is connected in parallel by the TK75's contact design.

Now the effect of this is that combined the cells are get 2S4P (remember that the total number of cells for XSYP = X x Y, so 2S2P has 2x2 or 4 cells and 2S4P has 2x4 or 8 cells).

The reason for talking about this is to reinforce the most important principles when combining cells.

If using cells in series, it is very important that they are as well matched as possible in capacity, charge level and that they are protected.

However, when using cells in parallel, this capacity matching is far far less important. In fact the only really important factor when using cells in parallel is matching the charge level. (Note that cell age can affect its ability to hold full charge, so cells should be similar in age - and age refers not just to calendar age, but to cycles as well).

When you have cells working in parallel (or even batteries - being a collection of cells), each individual cell will work together with the others, and if one cell is weaker, the others will simply work a bit harder. All the cells are linked in voltage, so it will be the strongest cell that works hardest. If you have one 2600mAh cell with one 3400mAh cell connected in parallel, during use, the 3400mAh cell would normally maintain its voltage better than the 2600mAh cell, but when working in parallel, as the load causes the voltage of the two cells to drop, the stronger cell will take the load off the weaker one but the cell voltages will stay the same.

So take this to the TK75's configuration...

The TK75 can run on 2 cells as long as you install these in 2S1P configuration (one cell with +ve facing towards the LED and one towards the tailcap). These cells are one 2S1P 'battery' and need to be closely matched.

Theoretically, you could now use 2 matched cells of a different capacity to make up the second 'P' part (to make it 2S2P), however it is far easier to avoid mistakes, by using a set of 4 matched cells in the TK75's battery carrier.

That is one battery carrier, so when moving onto a second one (which will be connected in parallel), the theory of using cells in parallel comes into effect. So if you have a second set of 4 matched cells that you can keep together in the second battery carrier, this will then be working in parallel with the first battery carrier so the actual cell capacity is not important, only the level of charge matters.


So despite the overstated paranoia regarding li-ions on CPF, given a bit of logical thought, I personally would be happy to use the cells as you described with 4x2600mAh in one carrier and 4x3400mAh cells in the second. I am happy to do this ONLY because they are used in parallel, if the combination of battery carriers was in series, I would not consider this safe.

Before doing this I would ensure all cells are charged to the same state of charge (measure the resting voltage of the fully charge cells), and each set is kept together and never mixed between the carriers.


Yes, ideally, in an ideal world, and one in which money is no object then get 8 new matching cells, but in the real world where money is a consideration, as long as you think about what you are doing, you don't need to buy 8 new cells, the four you are thinking of will be fine if used as I have described.