Same issue with my aged Dell Vostro pack which have nine Sanyo Blue top cells.
I use Xtar VP1 try to charge at 0.25A and/or 0.5A, when it reach around 4.14V, it start slowly heats up and voltage start to drop to 4.11V.
And so I monitor few more hours into charge still at 4.11V and it was very warm to the touch.
Yes all nine of them having the same issue. I repack all of it carefully and into recycle bin they went, not worth the risk :weary:
Greater internal resistance. Do they take longer to charge too?
No. they charge same as others. Maintain 3.6~3.7V under 1A load. And this thing happen only after cell reach over 4.1V. it keep cool during almost empty to 4.1V
I had that batteries too. same problem.
You can use a resistor load to measure the internal resistance if you have a multimeter:
Can you measure how much the temperature increases?
Some batteries have a temp rise when approaching full charge.
In the CV phase / saturation charge, with some batteries the current may level off and won’t drop any further. This is “fully charged” for that battery.
The capacity test ~1200mAH, what type of charge was that? 4.10v, 4.10v rest then charge to 4.20v, pushing through to 4.20v (heating up) without rest?
i bet they self discharge badly too.
run them down and recycle.
this is a BIG BRIGHT RED FLAG!
they are growing dendrites and could short without warning.
i had some that were ok till they crossed the 4v mark.then they dropped and the current stayed at the max of my triton.
thats 2.5a.a reasonable rate for 6p 18650.
they all got hot. later they sat at 2.8 or so after hitting 4v and putting in 10ah!
1200mAH capacity test was battery charged to 4.1V (I disconnect charger when cell start to heat)
charged with IMAX B6, TP4056 USB charging board & CC/CV Lab psu too. same
charged 4 cells to 4.2V after rest few hours. I will keep them another day and check voltage again.
Sorry to bump old thread but have some problem with 12 Sanyo UR18650A from 2 battery packs.
They were 3-3,5V when extracted.
They get extremely hot when charging…take them to recycling?
yes.
sanyo cells seem to fail this way.
dont be sorry.you added another data point to the database.this is a good thing.
If I had a cell that wouldn’t reach 4.2 volts it would be gone that day. I have some older cells that take a little bit to reach the end of the CV stage. But always complete. No way I’d let it continue at that stage for hours like one guy said he left it on for 10,000mah no way in hell. Cells are to cheap to risk any venting situation even though the new cells don’t really make flame anymore. I don’t want any cells to vent in my charger. I’d hope my vc2 would shut down when it heated up. I know the vc2 won’t charge a cell with a really high IR. Unlike some dumb smart chargers
Recycling it is 
Interesting is they reach 4.2V normally and in normal time and capacity if I let them cool for some time, othervise thermal protection in my Lii-500 stops charging.
just last week I had a cell get hot at 4.10v too …. An old ur18650 sanyo
Took it off the charger MARKED IT and finished it on another charger to 4,20+V … just checked it after a week of sitting and it’s 3.90V….Wow !! I’ve never seen a cell freefall like that
I believe Sanyo are the worst cells to find in a salvaged laptop battery pack. A youtuber actually went through a hundred or more laptop battery packs to salvage cells for an additional pack for his Nissan Leaf.
Here’s the link:
Complete 18650 data video
It appears that Sanyo were the worst performing cells by far and the Panasonics and Samsungs reined supreme. This is based strictly on the cell’s ability to maintain it’s original capacity. The guy in the video first charges the batteries to full and puts them on a 1A discharge test, records the mAH, recharges to full, let’s them sit for 30 days, and discharges them at 2A only if the voltage dropped no more than 0.04v. His data in the video is very organized on excel and his test methods appear to be very solid.
i put 10,000 mah into 6 parallel cells before they heated.they did NOT continue to charge for hours!
i watch things carefully when charging pack pulls.
its been my experience that sanyo cells in junk laptop packs are worn out rather than an arbitrary shutdown by the packs bms.i have some very old red sanyo cells that are still in great shape.and have been used daily.but they dont seem to last as long in a hot environment like a laptop.best so far are panasonic 2900 from lenovo packs.bms limits them badly.like planned obsolescence.never a bad cell or any reason for the pack to shut down. most have 2750 at that point.and still 60mohm ir.
like new for use in a laptop pack or anything else but subohm vaping.but even new they are not suitable for that.
I’m sorry to revive an old thread, but I’m not sure where else I can ask this.
I just got 2 of the On The Road U16 and for some reason one of the cells doesn’t want to charge fully to 4.2. I tried it on my Xtar VC4 and it seems to max at about 4.13v and then get really hot. I started charging from 3v. The cell capicity for the Orbtronic 16340 cell is 700 mah and typically measure 670-680 mah. This one cell will go on and on, past 900 mah and get really hot. Almost too hot to hold.
Would this be a sign that this new cell is defective?
I was always under the impression that when a cell gets overly hot that it’s either worn out or defective. With laptop pulls I had a number that got fairly hot like yours and never charged over about 4.10 or so. They were 2600mAh Sanyo’s and only discharged about 1000mAh. Does your 16340 cell lose voltage overnight? My bad ones dropped about .05 volts in around a day or so.
To be on the safe side I tossed those batteries.
Hey, that’s exactly the same thing that happened to me!
A few short months ago, I couldn’t find where to source 18650 batteries (I had just bought a generic XML T6 flashlight that uses 18650 cells).
After looking around forums, I note that these could be harvested from laptop battery packs, so I asked some relatives and friends if they have old laptop battery packs that may be bad and they’re not using anymore. I got 2 laptop battery packs from them (both were deemed ‘bad’ already). One contains 6 Samsung ICR18650-22F (4 were still usable, 2 were 0volts and nothing I did could recover them). The other contained 6 Sanyo UR18650A.
I bought and used an XTAR VC4 charger (that was my only Li-Ion battery charger at that time; aside from the cheap single-18650 charger that came with the generic XML T6 light) to charge the Sanyo UR18650As.
I left them for a few hours, when I came back, the capacity reading on the VC4 were already 2500+ or 3000+ mAh (which shouldn’t be possible since the rated capacity for them are 2200mAh — I was largely ignorant about 18650s at that time). Also, they were very warm or HOT (for some). The voltages were in the 3.93-4.03v. I removed the 18650s to let them cool. Then after they were cooled a few hours, I charged them again, and this time they charged to near or around ~4.20v but they don’t seem to terminate charging (I was monitoring [I touched the batteries every now and then to ‘check’ temperatures] the charging process at this time when I learned the 18650s could get quite HOT).
If I remove those batteries and then place them again in the XTAR VC4, they will now terminate charging properly.
They also don’t seem to discharge fast (leaving them for several days, only got them to around 4.10-4.15v (is this normal or is this fast self discharge?). A discharge capacity test (using EBD-USB+ load meter and an 18650 battery holder) showed they had around 900-1200mAh.
My experience (I’m new to 18650s, less than 6 months ago since I first recognize what is an 18650 battery) appears to exactly mirror the OP’s experience 3 years ago.
All the 6 Sanyo UR18650As had this overheating problem (but the lowest capacity one [around 900+mAh] is most likely to heat up first, the 2 higher capacity ones [around 1200+mAh] seems to be slightly less likely to heat up)