>>>>>I have some new, fresh, unused versions of these cells and they do the same thing.
Yeah, like I said, the newer higher-capacity Panasonics don’t seem to hold a charge like the old ones. I have like 25 Panasonic CGR18650D 2400-mah pulled cells that hold a solid 4.2 volts for 2 months or longer. And work like workhorses; can’t tell the diff in runtime in or output between them and the 2900s. Really.
Ditto for the newer samsung pinks (2600) and purples (2800 I think). Ditto for even the ancient Panasonic lime-green 2000s or CGR18650CE (2250 mah). Hold a solid 4.2 volts for months. And those latter two be OLD. In fact, the runtime isn’t so great. I suspect they have been beat to heck and back, but they still hold that 4.20 volts for 30 days or more.
I mean the panasonics are great cells and all, but that’s why I have been shying away from them and liking the samsungs more. What’s the sense of charging a battery and going to use it 30 days later and finding it at 4.05 or lower?
Having said that, I have found with panasonics 2600 and higher, if you cycle them 10-20 times, they seem to hold a chrge mUCH better. But not one cycle, wait a week, then another cycle, wait a week. What seems to work is run it down to 3.75 volts; charge it again; run it down the next day; charge it up; run it down the next day. Then they seem to hold it okay.
The 2200 (light green) and gray (2400) samsungs have the same problem. In fact, maybe only 5 out of 30 gray samsungs I have found were worth keeping. But then I don’t know their life history as I pulled ’em from packs.
I’m finding that samsung pinks and purples and panasonic 2600s are my best performers. I know that may not be what the charts and tests say, but when I get back home after about six months of my usual nightly desert walks, those are the cells that always read the highest remaining voltages in all kinds of lights. That’s a mix of new and pulled cells.
Just saying. IMHO. Not my intention to start a big my-battery-is-better-than-yours hoo-hah.