Odd RCR2 behavior

[moshow9]

Some quick background.. at the moment I own 15 li-ion batteries. A number of the small cells include 10440's, IMR 123, IMR 18350's, and RCR123's (all AW's). For these small cells I use Cottonpickers USB Charger with voltmeter display, current set to 90ma.

Recently I ordered 3 RCR2's and am baffled/concerned. Here is a look at what I am seeing at the start, during, and after charging is complete, compared to a 10440 I had also received in the same mailing:

10440
Starting voltage: 3.9v (as received)
Termination voltage: 4.2v
Time to Termination (@90ma): ~1hr57min
Resting Voltage (after 12hrs): 4.18v

RCR2
Starting Voltage: 4.03 (as received)
Termination voltage: 4.2v*
Time to Termination (@90ma): ~3hr30min*
Resting Voltage (after 12hrs): 4.09v

*I repeated the tests with the two other RCR2 cells. Both charged in the same manner, however, 1 was different. As it was charging, the display indicated 4.20 and held there for approx. 1.5-2hrs as it neared termination. Once the charging led went out termination was reached, however the voltage now indicated 4.13v. I rechecked with a digital multimeter and it confirmed the cell was at 4.13v.

At first I thought it might be the charger that is going bad. I put the rest of the 10440 cells (including older ones I had on hand), a few other RCR123's, and IMR123's to charge and did not observe any oddities.

I then went back to the RCR2 cell that ended at 4.13v and set it to charge again. Sure enough, the charging led lit back up. Roughly about an hour later it went out at ended at 4.19v. Unfortunately, after resting it also dropped to 4.09v. Once they drop to 4.09v they seem to stabilize and hold there.

This is the first time I have observed anything like this. While I am confused and want to understand what is happening, my primary concern is the safety with regards to these RCR2 cells.

 

[45/70]

Hi moshow. It would appear that you have obtained some older RCR2 cells. While it is rare for a LiCo (ICR) cell to maintain the same voltage 12hrs later, as it had when removed from the charger, your cell's voltage retention is considerably lower than normal, for "new" cells. Newer cells will often drop from say, 4.19 Volts off the charger, to 4.18 Volts in 12 hrs. The older a Li-Ion cell is (any type), the more the voltage will drop after resting, after being fully charged.

This is the nature of all Li-Ion cells. They begin to degrade whether they are used or not, from the moment they leave the factory. Your RCR2 cells likely sat around for a while before they got to you. This is not unusual, particularly in the "off" sizes, such as RCR2/15270. The demand is much lower and they don't move as fast.

Also, from the voltage reading you read after receiving the cells, I'd say the storage voltage was a bit high. This will speed up cell degradation as well, especially if the cells were stored in a hot warehouse for a period of time. Most LiCo cells are charged up to only 3.8-3.9 Volts before distribution. Limiting the storage voltage slows down the decay process somewhat, as compared to storing at a higher voltage, and helps to prolong cell life.

Your cells may still be useable. One of the parameters for determining when to recycle/dispose of LiCo cells due to age or use, is if the voltage drops to less than 4.00 Volts within a day after charging with a 4.20 Volt CC/CV charger, such as Cottonpicker's.

Some of the other guidelines for determining if it's time to recycle Li-Ion cells are if a cell will only retain 70-80% of it's original capacity, if a cell does not maintain voltage well under load, or the cell heats up when charging, at a moderate rate.

If I were you I would contact the seller and see what they have to say. At any rate, it appears to be the cells, not the charger.

Dave

 

[moshow9]

Hi moshow. It would appear that you have obtained some older RCR2 cells. While it is rare for a LiCo (ICR) cell to maintain the same voltage 12hrs later, as it had when removed from the charger, your cell's voltage retention is considerably lower than normal, for "new" cells. Newer cells will often drop from say, 4.19 Volts off the charger, to 4.18 Volts in 12 hrs. The older a Li-Ion cell is (any type), the more the voltage will drop after resting, after being fully charged.

This is the nature of all Li-Ion cells. They begin to degrade whether they are used or not, from the moment they leave the factory. Your RCR2 cells likely sat around for a while before they got to you. This is not unusual, particularly in the "off" sizes, such as RCR2/15270. The demand is much lower and they don't move as fast.

Also, from the voltage reading you read after receiving the cells, I'd say the storage voltage was a bit high. This will speed up cell degradation as well, especially if the cells were stored in a hot warehouse for a period of time. Most LiCo cells are charged up to only 3.8-3.9 Volts before distribution. Limiting the storage voltage slows down the decay process somewhat, as compared to storing at a higher voltage, and helps to prolong cell life.

Your cells may still be useable. One of the parameters for determining when to recycle/dispose of LiCo cells due to age or use, is if the voltage drops to less than 4.00 Volts within a day after charging with a 4.20 Volt CC/CV charger, such as Cottonpicker's.

Some of the other guidelines for determining if it's time to recycle Li-Ion cells are if a cell will only retain 70-80% of it's original capacity, if a cell does not maintain voltage well under load, or the cell heats up when charging, at a moderate rate.

If I were you I would contact the seller and see what they have to say. At any rate, it appears to be the cells, not the charger.

Dave

Thank you Dave for a very thorough explanation. Cheers :)