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Posted: 2/18/2006 8:54:32 AM EDT
I have an M3 light with two 3 volt Lithium batteries.

I just tested the batteries with my voltmeter. They read 2.98 and 2.95 volts respectively.

My light fails to come on. The last time I tried the light, it shined very dimly for 20 or 30 seconds and then went out. But today, no light at all.

Are these batteries dead?

Should I look elsewhere for the problem?

Thanks,

viator
Link Posted: 2/18/2006 9:25:43 AM EDT
Link Posted: 2/18/2006 9:31:35 AM EDT

Originally Posted By BrightFlashlights:
The batteries are 'dead' so to speak, most of these high power 6v incandascents fail to light if the combined voltage drops below 2.8-2.9 volts.

The dead cells will still run fairly well in certain low output and 1w LED's if you want to get all of the juice out of them.




Thanks for the help. The voltage seemed to be fairly high, compared to the batteries I have tested in other types of lights. I was sort of surprised that these didn't work.

Your explanation helps me to understand why.

Thanks,

viator
Link Posted: 2/18/2006 9:35:16 AM EDT
Link Posted: 2/18/2006 9:38:14 AM EDT
when the lithium batts die they just die, no slowly fading light light a regular battery, at least not as long
Link Posted: 2/18/2006 9:42:23 AM EDT

Originally Posted By BrightFlashlights:
The basic voltmeter won't give you an accurate assesment, if you had a load tester it would show the cells were much weaker.



That makes sense.

Danke,

viator
Link Posted: 2/18/2006 9:47:38 AM EDT

Originally Posted By twonami:
when the lithium batts die they just die, no slowly fading light light a regular battery, at least not as long




That is what happened with this light. I have had it for years, but use it infrequently. It has been mounted on one of my Glocks that goes to the range and then back in the safe.

I tried the light a while ago and it came on briefly and then went out. I tried it a time or two after that and it did the same thing. Then, nothing. There was not much of a time lapse between lot of light and then dim and then nothing.

Since it was not on my primary home defense weapon, I wasn’t all that concerned about it. A Saturday morning like this seemed like a good time to get it up and running again. It just doesn’t make sense to have a non-functioning light!

viator
Link Posted: 2/18/2006 12:31:26 PM EDT
This is a good question. Since I know I won't get any warning, I decided to avoid problems. When I know I've used a set of batteries in an "important" light (like my primary light I wear on my belt or one the light on a rifle) for a cumulative 15-20 minutes, I install fresh batteries. Then I use the partially used batteries in "less important" lights, like those I keep around the house for utility purposes, or even for a camera.
Link Posted: 2/18/2006 12:48:47 PM EDT

Originally Posted By BrightFlashlights:
The basic voltmeter won't give you an accurate assesment, if you had a load tester it would show the cells were much weaker.




I don't have a load tester.

How much do they cost?

Do you sell them?

If not, where might one purchase a load tester?


viator
Link Posted: 2/24/2006 9:46:35 AM EDT
Seems like you could put in new batteries and find out if that works... they are so cheap just throw the old ones away!
Link Posted: 2/24/2006 10:15:25 AM EDT

Originally Posted By viator:

Originally Posted By BrightFlashlights:
The basic voltmeter won't give you an accurate assesment, if you had a load tester it would show the cells were much weaker.



viator



A digital multimeter with an Amperage scale can be used to determine the current drain from the batteries under actual operating conditions. Remove the tail cap, and touch one lead to the bare metal casing where the threads are exposed, and the other lead to the end of the exposed battery.

If there is a side switch, it must be on also. Lights with electronics/switching in the tail cap can't be tested as conveniently.

For example, a Surefire P90 lamp draws ~1.17 amps. IIRC the P60 is about the same. At that level the actual battery voltage drops MUCH lower than what you would measure with the Voltmeter function and the battery out of the circuit.

The Surefire KL-3(gen I) LED head only draws about 0.21 amps, so it can easily be powered by batteries that are no longer capable of lighting an incandescent filament.

Connected incorrectly, a meter acts like a dead short, something you should NOT do to a high power lithium cell, BTW. HTH.

Paladin
Link Posted: 2/24/2006 1:40:34 PM EDT

Originally Posted By PALADIN-hgwt:

A digital multimeter with an Amperage scale can be used to determine the current drain from the batteries under actual operating conditions. Remove the tail cap, and touch one lead to the bare metal casing where the threads are exposed, and the other lead to the end of the exposed battery.

If there is a side switch, it must be on also. Lights with electronics/switching in the tail cap can't be tested as conveniently.

For example, a Surefire P90 lamp draws ~1.17 amps. IIRC the P60 is about the same. At that level the actual battery voltage drops MUCH lower than what you would measure with the Voltmeter function and the battery out of the circuit.

The Surefire KL-3(gen I) LED head only draws about 0.21 amps, so it can easily be powered by batteries that are no longer capable of lighting an incandescent filament.

Connected incorrectly, a meter acts like a dead short, something you should NOT do to a high power lithium cell, BTW. HTH.

Paladin




That does help. I can do that.

In fact, I will.

viator
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