Fenix TK50 constant on problem

So I made my purchase of a Fenix TK50. Nice light indeed, however I am now having issues with the constant on modes of which there are 4 .... low, med, high and turbo. With really cheap batteries I can get all four modes but when I swap those batteries for better ones like the Energizers I turn the light on and it appears to start off in medium. Then when I click again nothing happens then I click and get high and then turbo. So with cheap bateries I get all 4 modes ok but not so with the more expensive batteries. I can only think that as the Energizers may be over (and are) the 3.0 volts total that the light recognises that as too much for it so rather than giving me low it gives me med. Any suggestions??

That is unfortunately a "feature" of a few Fenix 2-cell AA/D lights. With fresh alkalines, the voltage is too high for the driver to properly regulate low. You end up with something between low and medium instead. My TK50 does the same, as well as my ld20. I use only NiMH on them, and this mostly solves the problem - except for "hot off the charger".

Thanks very much for that ... could I ask therefore if once the voltage has dropped if I can expect normal operation. I guess the answer would be yes but only someone who has got that far down the track would really know.

That would be yes. If you leave it on low, it may take a while to get the voltage low enough, but a few minutes on high did the trick for me the first and last time I used alkalines in my TK50.

I've never used, or will use alkaline batteries in my TK50, only eneloops in D adapters (2 in each ) Never had a problem with this setup..

Thanks all. Will try and run down the energizers to see how long it takes to click into normal 4 modes of constant on. I am offshore to the US so wonder how I can get these AA adaptors to allow use in the TK50. I can buy eneloops here and use these in my Zebra light but wouldn't know where to get those gizmos so I can use the same in the TK??

I got my D Cell adapters from here. Cost $2.68 each with free shipping.

http://kaidomain.com/ProductDetails.aspx?ProductId=2710

Thanks again. I note that you show a pic of the TK50 with the adapters and each adapter has 2 x AA's inside however when using the TK50 should you not be using 1 x AA inside ech adapter total voltage 3.0 (2 x D's or 2 x AA's)?. As I am not familiar with adapters I have to ask.

The batteries in those adapters are parallel so the voltage is the same as if you only had 1 in each adapter.

There is also a 3AA version of these adapters available from dealextreme if you want longer runtime.

Thanks JacobJones, thought this could be the case but wanted to learn. I wonder if the run times would change or be differant that those stated when using the standard D size cells. I guess this comes down to the mAH's? One chart I read says 2000 hrs approx for the AA's and up to 17000 for a d cell so if I buy some adapters which would allow me to use the eneloops I have (AA's) th run time would not be as long as the D cells so maybe I am just better off with D's as run time is important.

I searched dealextreme's website and can't find the 3 cell version. Do you have a link?

How odd, I can't find the product on dealextreme. I guess it must have been a different seller that had it

I also note that at the end of life of the batteries that the turbo mode is lower in intensity than the high mode again showing that the light will neither perform perfectly when the batteries are brand new (if hig quality ones) due to the hig voltage nor when they are at the end of life as the light tries to work out what to do with both high and low volatges. Thsi turbo mode not being as bright as the high mode is happening with the low quality batteries I have in the light but I suspect the same would happen with any battery variation as you cannot expect turbo mode unless you have enough juice. Really enjoying this light.