ARC-P DS weird behavior

Last November I bought two DS, one for me and the other for a friend that is deployed to Afghanistan. This week my Arc started to do strange things. First, it suddenly went down. I thought that maybe the problem was with the contacts. I cleaned them and it did not work, then I changed batteries and it worked, so I thought the battery charge was depleted, although it did not go into "moon" mode.
I put the old battery back and to my surprise it worked. I switched it on on off a few times and it still worked. After 1 hour after switching it off I had the same behavior (works with new battery and with the old one back and after a while it does not work with the old battery). The problem is that I think I am getting less runtime than expected since it suddenly shuts off.
Any suggestions? Should I send it back to Arc?

Just curious. Is the negative end of your AAA battery dented? The spike-shaped negative contact inside the Arc's battery case dents my batteries.

What you're describing is characteristic of a run down cell. It takes a higher voltage to 'fire' the ARC than it does to run it. Letting the cell 'rest' allows the voltage to recover enough to fire it again.

I use lithiums in mine and sing the praises of all the positive stuff about them, but the one negative is that I get almost no warning of when it is depleted.

I will have used the light and with no problems and the next time I go to use it - it won't turn on. I realize after the fact that the light had been dimmer for quite a while, but when you only use it intermittently for short periods, I often don't notice the dimming.

I'm guessing that you're using the ARC more than you think that you are, but the easy way to tell how it's working is to do a run time test. Use a new inexpensive alkaline and time it.

Thank you. On the Parnass' question about the dent on the battery, yes. It has a small dent on the negative side. Kitelights, I will follow your advice and make a runtime test. I will make it after I test the battery with my old CS (that is now on my wife's keyring). If it does not work, I may conclude that the battery is dead and that I am using the light more than I think I did. I will check with the runtime test.

What confused me is that I did not experiment the same behavior with my old CS. I will pot the results of my runtime test as soon as I can.

That happened to me this weekend! About 2 weeks ago I thought I saw the moon-mode flicker. I used the light to read and went to sleep. It did not turn on when I got up to use the bathroom. It was a lithium cell. I changed the battery the next morning and all is well. The cell that died has been in service since I got my DS in October.

kelmo