K2 Kroma on batterystation rechargeables

LED61

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I have learned a lot from good folks here at CPF, now I thought I'd give something back. After much debating and consulting great people here, I finally decided to go ahead and try my new Kroma on rechargeables RCR 123's, as well as some other batteries.

First off, let me begin by stating I am no expert, and my mini review here is merely an experience. I'll leave the volts-amps-tests to the real gurus, and if some of you can add to this post it will be greatly appreciated.

To power the Kroma, I ordered 4 types of batteries from Kevin at Batterystation.com. These were:

1) 900 ma batterystation yellow-red RCR 123A 3.6 volt
2) 1500 ma 17650 (168S) rechargeables
3) Sanyo made in China CR 123A primaries
4) Batterystation 1300 ma CR 123A primaries

I began by fully charging two brand new batterystation RCR123A's, and then let the cells "cool" for four hours. Each of the cells was then run at a timed 15 seconds in my Peak CPF Special to hopefully get rid of any voltage surge on startup for the Kroma which is regulated, whereas the Peak is direct drive--no risk there. Then the cell went into the Kroma body with a slight push, a bit snuger than primaries, but no sweat. I could tell though that after the run and the increase in temperature I was probably going to have to put up a fight to get the cells out.
Then--pum!! the light turned on and I was very relieved to see everything went alright, with no alteration in brightness in the high beam from that of the primaries. I went direct to high beam and did not do any tests on the other modes. the light was placed over a cool granite top, ambient temperature was 80 F. It quickly warmed up--first the head, then progressed slowly toward the tail switch. the light reached maximum temperature after about 20 minutes, and after I picked it up I could tell my hand helped to cool it. It was very warm yes, but not uncomfortably hot to the touch. It never reached an uncomfortable temperature through the run test. past 45 minutes and I began to closely monitor SilverFox's runtime test for those cells in his thread. I knew from LedMuseum's review of the light that it was drawing approximately .8 amps, and the runtimes for the cells at both .5 and 1 amp are between .5 and .6 hours for one cell.

At exactly 57 minutes runtime the batteries (one or both?) protection kicked in and the light shut down immediately without lowering the output in the course of the runtime. I opened the light immediately, and only had to shake the light violently for the bottom cell to come out. The cells were nice and cool, much cooler than the light's body.

I sat down to write this review, there is one 17650 fully charged battery awaiting its turn but I did not want to be distracted so you'll have to wait a while to read its performance:whistle: don't worry, I will test all 4 batteries on the light and will edit the post as I go along. But these cells worked beautifully on the light, at least apparently so.

--the batterystation 17650 (168S) 1500 ma WILL FIT the Kroma but you have to unscrew the head and tail, and do a little pushing towards the tail, in other words, push from the positive side. Be careful to not overpush, as the battery will fit in so snug that contact will be lost. You have to leave the positive side up a little and push the final amount with the head...slowly. Runtime is an impressive two hours and 24 minutes in high beam white only...not bad. All functions in the flashlight worked beautifully and I even felt less heat than with 2 RCR's. This seems to be the best alternative. The light runs very cool throughout and after this I'm not even going to bother with RCR's anymore. The RCR's heated the light so much more. Some beam weakening was noticed toward the end but hardly. After this, I'll run my Kroma this way.
 
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Geogecko

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I knew from LedMuseum's review of the light that it was drawing approximately .8 amps, and the runtimes for the cells at both .5 and 1 amp are between .5 and .6 hours for one cell, make it double for the two in series I was using.

Nice review, BTW.

This comment is not quite correct though. Batteries in series increase voltage, not capacity. Batteries in parallel have the same voltage, but increased capacity.

For example, if you have one battery at 3V, 1500mAh, then with a 1A load @ 3V, that would run ideally, for 1.5 hours before being finished. On the other hand, if you put 2 of the same batteries in parallel, that would give you a combination of 3V at 3000mAh, so the same 1A load at 3V would provide 3 hours of operation.

However, it gets a bit tricky here, because when you start talking about switching regulators, which I'm sure the Kroma is, things change.

If the LED voltage is say, 3.6V or so, then obviously, in a buck only mode regulator, you'd get direct drive output (3V) from the battery. With 2 3V batteries, you'd have 6V at your disposal, so a buck type regulator would regulate the voltage with a certain efficency (maybe 85%), giving a false impression that putting batteries in series actually doubles their capacity.

Since you have more voltage to play with, and the regulator does not waste much power (15%), then it requires less current to generate that 1A of power needed by the LED (say, 0.7A instead) on the battery side of the regulator.

I'm sure you didn't want this OT discussion, but just thought I'd add a little to it...
 

LED61

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You are actually correct and thanks for the correction....I guess what I meant to say was just that...having two batteries instead of 1 would double the runtime in SilverFox´s review of the single battery, at the specified amp draw as per LEDMuseum´s review of the Kroma.
 

RadarGreg

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I'm still having the problem with the 17670 battery running the Kroma-MS properly. The battery fits just fine, but when you turn on any of the lights, the main white beam comes on as well as any of the other colored LEDs you've selected. I'll have to get a 17650 battery and try it, but I'm still not going to recommend to anyone to use the 17670 battery as the output function is not correct. Perhaps this is just a case of a bad battery, but will have to try another one to verify.
 

LED61

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RadarGreg, do you consider the possibility of a fault in the circuit of that particular light? have you tried this in another one of the milspecs you have access to? I've been through four different recharging cycles with two different same type battery and no issues. I'm amazed at how cool the light runs and the high beam white is indeed powerfull. All modes work as they are supposed to.
 

RadarGreg

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LED61 said:
RadarGreg, do you consider the possibility of a fault in the circuit of that particular light? have you tried this in another one of the milspecs you have access to? I've been through four different recharging cycles with two different same type battery and no issues. I'm amazed at how cool the light runs and the high beam white is indeed powerfull. All modes work as they are supposed to.

I'll be back in Iraq in two weeks and will try it on one of the lights there. I hope it just a defective battery. It runs perfectly on two RCR123A batteries or on standard CR123A cells. A defective Kroma would be so sad...
 

LED61

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RadarGreg said:
I'll be back in Iraq in two weeks and will try it on one of the lights there. I hope it just a defective battery. It runs perfectly on two RCR123A batteries or on standard CR123A cells. A defective Kroma would be so sad...

I've thrashed the idea of running my Kroma on RCR's. Heat is outrageous compared to the one 17650. I suspect the heat is caused by the resistors in the regulator circuit having to absorb the extra voltage. Besides, one battery is always better than one. The 17650 runs the light beautifully, and very cool. Even cooler than on primaries. Runtime is well over 2 hours with a very nice high beam.
 

benighted

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Hi LED61,

Thanks for the short review of the Kroma on rechargeables.
Do you notice any loss of output when comparing primaries to a 17670?
 

LED61

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benighted said:
Hi LED61,

Thanks for the short review of the Kroma on rechargeables.
Do you notice any loss of output when comparing primaries to a 17670?

Yes, most definitely there is probably a 10-15% at least- reduction in total output. But, for the light´s intended use it is of no issue to me. Runtime is great, and the light runs a lot cooler for a longer time.

Alberto
 

dchao

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LED61 said:
Yes, most definitely there is probably a 10-15% at least- reduction in total output. But, for the light´s intended use it is of no issue to me. Runtime is great, and the light runs a lot cooler for a longer time.
To my naked eyes, the outputs appear to be the same (mind you, 10% light change is very hard to detect by eyes). I think this is attributed to the use of lower Vf Luxeon III LED (instead of Lux V as in U2). If the Kroma has a simple buck type converter, it should be able to hold the 750mA quite easily.
 

LED61

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Hmm the single 17670 gets down to about 3.5 volts and I don´t think the Kroma runs full blast when the 2 in series primaries add up to this. I see it is also noticeable dimmer than my U60 side by side and my peak special. When I switch to primaries I do notice a slight brighter output. But I agree with you for all practical purposes the light is fine when ran with the 17670.
 

dchao

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Re: K2 Kroma on battery station rechargeables

K2 Kroma works with unprotected 17670 (from either AW or Lighthound) and it fits perfectly.

Unprotected 17670 is both shorter and thinner than the protected one, and it fits so perfectly inside the Kroma. Even the switch spring tension is maintained.

However, I have to use a little magnet spacer on the anode so it touches the little spring contact in the head assembly. I also use electric insulation tape to make sure the spacer can never get knocked off center and shorted to the cathode.

EDIT: I can also verified that the 17670 runs very cool in the Kroma, the body, after 10 min is still cold to the touch.
 
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