Hmmm... Funny thing just happened. Can someone explain?
I used my 2x18650 L2x with 1-mode XML for couple of hours non stop. Untill it the cell protection kicked in and the light went off. Out of curiosity I measured the voltages. Other cell 3,04V. Ok, that seems fine. Other cell, 0,0V. I kid you not. It couldn't be the DMM, because it measured the other cell (and couple of others I tested when thing got weird) fine. Then I thought the leads were misplaced and tried again, like 10 times. No matter how I placed the leads, nothing.
Then I charged the buggers for 5 mins. After that I got 3,2V from both cells. Is this something I should worry about? Both cells look just fine, no bulging or any abnormal shaping. Both cells were equally warm after cut-off. Weren't hot, but warmish. Cells in question were blue Cytac 2600 mah, which should be quality stuff. At least I paid like 15 euros a piece. (which is just plain stupid on my behalf, but let's not focus on that)
The protection circuit needs to be reset. Pop it in the charger for a minute or two and it'll give you a voltage. The protection circuit needs to keep the cell shut down till it is recharged or someone will discharge it below the cell damage level.
This is how the protection circuits are supposed to work and is not anything to worry about.
Just make sure you don't mix partly charged cells with freshly charged cells in this 2x18650 setup. You want to make sure both of the cells have been fully charged so that will discharge at as close to the same rate as possible.
I've noticed the protection kicking in on one of my 18650s as well, but it was doing so at essentially full charge, which is odd. This happens once in awhile with an underdriven MC-E. Could the protection circuit be damaged? Does the protection measure voltage or current? Can I remove it?
with three of four flame trusties I have got recently. When I unwraped them they were all around 3,8 volts. I put them to the charger. Three of them show 0,0 volts after recharge. No way to do anything about it, exept tearing off the protections. Well, I think I have to file a complaint.