MJLED strobing?...

270winchester

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Hey FOlks:

I have a MJLED in my MM, and it worked great for a while. Two weeks ago while I was in Texas I left it on with two alkalines for about 160 hours and toward the end it still produced good light enough for a night light. I of course loved it.

So I put in some lithium AA's this monday, and to my surprise the LED strobed like crazy as soon asI turn the light on, and the problem intermittenly occurs on a regular basis. Anyone know as to why this might happen? I put it in a different MM and the same result happened. Alkalines caused the same result.

P.S., the MJLED apparently required quite a bit of voltage to workj since it didn't like NIMH AA's, and the seemly depleted alkalines cells I used for my run time test fired a NexGEn 750 with TWOJ right up, I was amazed. I ran for a good 30 minutes in the sammie before i noticed the dimming. DOuble weird....
 

wwglen

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MJLED needs somewere between 2.8 and 3.2 Volts to work properly.

Two Lithium are overdriving the LED (3.4 Volt @ 130mA for mine).

Two rechargeable batteries only give 2.5 volts at full charge.

With 1.4-1.45 volts left in each battery when you need to replace them there is still 80% or so of the charge still in the batteries.

wwglen
 

3rd_shift

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I have an mjled surgically installed direct drive in a Q3 running 50-80 milliamps direct off of a 3.1 volt cr123.
Even at just 60ma, the mjled hit a temp of 120 degreesF in only a few minutes.

Try a 26k led with the lithium batteries and see what you get.
I think you will be impressed with both brightness and an even longer runtime. /ubbthreads/images/graemlins/smile.gif
 

Bob_Ulhedd

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This problem has been mentioned before on Candlepower Forums. See this thread. I believe that Crossbar, who started the thread I linked to, mentioned on another thread that he used lithium batteries with the problem MJLED. I have also experienced a flashing MJLED after powering it with two lithium AA batteries. For a thread advising caution when using Battery Station AA Lithium batteries click here.
 

LEDninja

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I use RECHARGEABLE alkalines (pure energy / renewal) in my MJLED minimag. As soon as the light start to get dim (about 2-3 hours), I pop the batteries into the charger and boost it back up to 2x1.6V or 3.2 volts again. That way I do not waste the 80% unused battery capacity.

You could have damaged your LED by running it on lithiums.
 

WildRice

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the strobing is from a loose INTERNAL connection. When the die heats up the connection goes away, when it cools back off it re-connects (very quickly). from what I have seen, the strobing will turn into flashing, then it will just die, sorry.

Jeff
 

wwglen

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270winchester,

Send me an PM with your mailing address. I will send you a "Homemade" MJLED. This is a high power 100mA 5mm LED I got from a group buy, ground down using a dremal tool. Looks rough but the three I have are about the same (brightness and beam shape) as the third gen MJLEDs I got.

I will also toss in a 26K LED.

wwglen
 

Crossbar

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[ QUOTE ]
Bob_Ulhedd said:
This problem has been mentioned before on Candlepower Forums. See this thread. I believe that Crossbar, who started the thread I linked to, mentioned on another thread that he used lithium batteries with the problem MJLED. I have also experienced a flashing MJLED after powering it with two lithium AA batteries. For a thread advising caution when using Battery Station AA Lithium batteries click here.

[/ QUOTE ]
Yep, I smoked two MJLEDs by using Lithiums. I'm still disappointed because the site I bought them from recommended using Lithiums, and as a novice flashaholic, I didn't know any better /ubbthreads/images/graemlins/icon23.gif
 

wwglen

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I believe the First Generation MJLEDs needed the voltage from Lithiums to get a decient current.

The latter ones seem to have a lower Vf and with Alklines I get around 35mA.

wwglen
 

HaulinLow

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[ QUOTE ]
wwglen said:
270winchester,

Send me an PM with your mailing address. I will send you a "Homemade" MJLED. This is a high power 100mA 5mm LED I got from a group buy, ground down using a dremal tool. Looks rough but the three I have are about the same (brightness and beam shape) as the third gen MJLEDs I got.

I will also toss in a 26K LED.

wwglen

[/ QUOTE ]

wwglen, if you have "too many" /ubbthreads/images/graemlins/wink.gif of these homemade MJLed's I'm interested in buying two. PM if you want to work something out.
 

Prometheid

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Any idea what the failure rate is for MJLED and lithium AA?

with all the MJLEDs out there, maybe a thousand, how many are using 2AA lithium and getting away with it? Are failures rare, or common?

I really like the performance of this combo in my mini-mag, but if it only lasts an hour or so before failure.... I guess I'd have to use alkalines only, and that's not nearly as impressive.

Thanks for any insights.
 

chimo

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I found that with a recent uncut MJLED (from the shoppe) the forward current was around 200mA at 3.2 volts. That's way over rated current. I also found that they degrade quickly at around 100 mA.

Paul
 

Prometheid

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Chimo -- maybe that batch has such a low Vf that NiMH would be suitable?

Or maybe there's such wide variation that individual testing is required?

One of my MJs on fresh Energizer L91 lithiums draws 130 mA. I really like it, but I'm worried that the batteries will outlast the LED.

Thanks for again for any insights.
 

voodoogreg

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For use newbies's eap the one not with a lot of electronics knowledge, tend to just set a host LED , and batt and don't know it may need to be resistored.
I learned that with a 26K and a 3.7(4.2 off the charger)
AAA li ion. I really got the host and it's reflector tunes well, and know need to know were and how much resistor value to add! the batt is great but the 26 get's dimm only after one run on the Li ion. VDG


PS< I know you can put the resistor n the bottom spring, just not sure were to solder it. Anyone know a good site or thread to learn this?
 

chimo

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This graph will give you some idea of the current at various voltages for a few different LEDs. This is a sample size of one for each type so YMMV.

 
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