odd battery issue

[Virtual Life]

I have 2 unprotected NCR18650B's that I use in VTR's. I use the VW setting at 6-8 watts (well within battery capabilities). One of them started turning off in the older VTR (about 8 months of daily use) this morning. So I tried in the other VTR (new one not in service yet, but verified working) and it won't see it at all. Will not turn on. Back into the old one and it does have a green light, get one drag then turns unit off. Just goes dead as if I did not turn it on. As if there is short. Not warm at all. Volt meter shows 3.9, about right since after charging I used it 1-2 hours. I charge 2-4 of my 7 at a time in an Intellicharger so they do rest before/after charging.

The battery is one year old and extrapolating based on how long it lasts in my VTR and how many total batteries I have I think it has had about 75-100 cycles of charge/discharge.

I would accept that it just went bad over time, but 3.9 volts and not warm at all makes this a mystery to me.

Best guess is an intermittent short. Not worth trying to preserve it and it is retired, but this is a quest for understanding. Any ideas? Maybe retire the other one also? My newer ones are 10 amp NCR18650PD and I got 2 of them in February and 2 more in May (marked so I can tell the diff). Should I be replacing them soon also? My oldest is also one year, an EH IMR 2000mah. All of them are in rotation and get the same usage. Think I am lucky to last that long?

Since I am going to get more, perhaps I should be thinking about replacing them all? I can afford to replace them all, but if it works...

 

[Ryedan]

These batteries should not be worn out after 100 charge cycles, but I have no experience with these. I had a couple of MNKE that lasted around 200 cycles and I thought that was a bit low, but my Sony VTC3s are lasting longer in the same charger so maybe it's just that some batteries don't last as along as others.

I would check their voltage very soon after the charger finishes a battery. Should be 4.2v. If it's higher it will reduce battery life. If a battery is worn out it sometimes will drop voltage soon after charge is finished. New batteries only drop ~0.01v in the first couple of hours. Old ones can go down a lot faster.

The other thing that happens as batteries wear is their internal resistance goes up which causes voltage under load to go down. If this is the case with your batteries, your VTR might measure voltage under load and may be shutting down because it thinks the battery is empty. This doesn't explain why the other VTR will not even start up with a 3.9v battery though.

Let us know what voltage the charger leaves the batteries at. One thing at a time

 

[Virtual Life]

At first I thought my (old) VTR was having issues or I would not have tried the battery (again) multiple times. Too risky (to me) for these batteries, not worth pursuing.

It is the only battery that did this, I have zero doubt that something is wrong with that battery since the hardware accepts other ones. Been using same VTR now for 2 more days since then. I am not going to try recharging, not worth it for $10-12. I was just hoping someone who had a similar issue could shed some light on this event.

 

[Papa Lazarou]

I've got some unbranded IMR batteries that are a couple of years old and measure around 4v resting. But apply any sort of load to them at all and the voltage just collapses. They are useless. I wouldn't expect this of a high quality Panasonic battery after 100 cycles though, unless they'd been used beyond their capabilities.