Hitting overcharge voltage on new AW 18650

[NutSAK]

I've been using a DSD charger for about three years that has always reliably terminated at 4.18 - 4.22 volts. I check the voltage of all batteries coming off this charger when the light turns green.

I've recently purchased a button-top black AW18650 2200mAh that is showing different behavior than all the other AW Li-Ions I've been using (16340 and 18650). When I charge this 18650, the charge terminates in error (red/green LED flash) and the battery tests at 4.20 volts. It appears that the overcharge protection of the battery is kicking in before the DSD determines that the charge is complete.

I contacted the battery retailer about this, and they sent a replacement 18650 that does exactly the same thing. I've since charged all the other Li-Ion batteries I own on this charger, protected and unprotected, and the DSD always finishes with a green light and a resulting battery voltage of 4.18-4.22 volts.

What is going on here? Is the protection circuit in these particular 18650s set to a more sensitive (lower) voltage threshold? Am I going to damage these batteries if I keep hitting the overcharge protection at 4.20 volts? Does the charger need to show a complete charge at a lower voltage?

 

[NutSAK]

Can anyone help me here? My apologies for the noob questions, but I was under the impression that protection circuits allow +/- 0.05 volt variances from 4.20. Therefore I assumed the 4.22 V that I get from this DSD charger would be in the acceptable range.

 

[Black Rose]

I have a couple of those AW cells and I charged them successfully with a WF-139, which is known to put extra voltage into cells, and it never tripped the PCB on the button top AW 18650 cells that I have.

I would check with AW about this.

 

[BVH]

I charged 6 of these cells (individually) on my Schulze to 4.2 - 4.21 with no issues.

 

[NutSAK]

I would check with AW about this.

Of course! I will do that.

Thanks for the replies!

 

[amigafan2003]

You need to monitor the "charging" voltage of your DSD charger. My old one used to spike at 4.27v at the end of a cycle with a battery in it even though the battery showed 4.2v when removed from the charger.

AW cells have an over charge protection circuit set to 4.25v - so giving it 4.27v is enough to trip it.

 

[NutSAK]

I have been monitoring it at 4.25 V toward the end of the charge. According to this post, I'm assuming that is correct.

 

[DM51]

4.20V is the maximum you should charge a Li-Ion cell. Anything above that will decrease the cell's cycle life. The higher you charge it above 4.20V, the fewer cycles you will get out of it.

 

[NutSAK]

4.20V is the maximum you should charge a Li-Ion cell. Anything above that will decrease the cell's cycle life. The higher you charge it above 4.20V, the fewer cycles you will get out of it.

I understand that. What I don't understand is why, out of the 6 AW cells I own, these two new 18650s are the only ones that trip at the 4.25 charging voltage. They come off the charger with 4.21 volts, which is no higher than the ones that complete the charge cycle.

I don't believe I've read of this issue with the DSD charger before, but I could have missed it. The transformer for the DSD is rated at 4.25 volts.

I am having a PM discussion with AW right now...

 

[NutSAK]

You need to monitor the "charging" voltage of your DSD charger. My old one used to spike at 4.27v at the end of a cycle with a battery in it even though the battery showed 4.2v when removed from the charger.

AW cells have an over charge protection circuit set to 4.25v - so giving it 4.27v is enough to trip it.

Just an FYI... AW stated that the battery protection circuit does not monitor charging voltage. It only monitors the voltage across the battery. So, a 4.27v charging voltage should not trip the overcharge circuit.

After trouble shooting my charger and these new batteries, AW and I decided both are functioning properly. It seems that the protection circuit in these particular batteries must be a bit more sensitive to overcharge than most, and the protection is kicking in at 4.21 volts. I actually like this, because it should prevent these batteries from accidental overcharging and reducing their lifespan.