Battery's minimum voltage in an SC600?

[bitcat70]

Hi!
First I'm not sure if this post belongs here or in the flashlight forum so please move it if this is the wrong one. I'm a new owner of an SC 600 flashlight (love it!). I got an AW 2900 protected cell for it and the Xtar WP2 II charger. I charged the battery and installed it in the flashlight. Lo and behold I experienced LIGHT! I didn't measure the voltage but I will next time I charge it. Which is now. In any case, yesterday I tried to use the flashlight and it turned on for a second and turned off. I tried a couple more times with the same result. So I pulled out my DMM and the cell read 3.4 V. Is that discharged? Or maybe the flashlight won't work with this voltage? But it would be strange because specs for the flashlight state: "Operating Voltage Range: 2.7V - 4.2V". Or is that the cell cutting out? Also I'm wondering if it's ok to fully run down such a cell in this flashlight? At this point I have a lot of questions...

 

[FreeMagenta]

Hello.

The battery is nearly overdischarged and probably thats why your light isn't working.

Fully charged AW 2900 (and nearly any 18650) should be close below 4.20V. Typical Li-Ion battery should not go below 3.6V resting.

When you will charge your battery, check if it isn't abnormally heating. If so, I'd advise discontinuing to use it. The battery should not be damaged, AW 2900 have more tolerance for deep discharge (mine got discharged twice to 3.4V - no capacity loss or internal resistance rising) - but still, with lithium batteries it still better to be careful.

Also, 3.4V resting woltage will fall instantly when the batery is put under load, so thats why your light is blinking:You are draining last remnants of power from the battery, its voltage drops instantly below 2.7V and the protection kicks in, cutting off the battery.

PS. Searching for "AW 2900 minimum voltage" should give you the answers without creating a new topic

 

[bitcat70]

Hi!
Thanks for the reply. I tried that search term but none of the results really answered my questions. Anyhoo... I charged the cell and took it out of the charger and measured the voltage. 4.27 V. Is that ok? The cell got only barely warm to touch during charging. Will it be ok?

 

[FreeMagenta]

It depends on your multimeter accuracy. The battery isn't heating, thats a good thing; still 4.27V can indicate a faulty charger - or really cheap multimeter . Do you have any other batteries that you can test in your charger?

 

[bitcat70]

The charger is the Xtar WP2 II one. The DMM was calibrated each year in my previous job. I forget the make but I don't think it is a cheap one. This being my first escapade into the world of Li ion rechargeable batteries and flashlights powered by them I only got one. I guess I will get a couple more. Can you recommend a store? And is there something to help organize/carry spares?

 

[bitcat70]

Ok. The DMM is Fluke 8020A. It's an older model but should still be good. So far the flashlight seems to be working ok with the cell. If I get the time I will try to get some runtime numbers and compare to an SC600 review.