I have an issue with 3 brand new EagleTac 17650 cells.
I popped 4 on my BTC-3100 v2 and 3 of them read 0.49v. (they showed as NULL on my other 3 chargers)
LiitoKala Lii-500 ~ MIBOXER C4-Plus ~ ESYB E4
They were charged to 3.7v and stored in battery cases, as are ALL my li ion inventory.
What would cause this severe voltage drop from sitting for 6 months?
They won’t budge on the charger - usually that BTC-3100 can bring back a low low cell for me.
This has never happened with any other li ion cells … and I have dozens of 18650 - 17650 - 16650 –14500
The internal protection circuit is always powered up by the cell and has a small but significant current draw over such a long time. Most likely that depleted your cells.
6 months is probably too long to let protected cells sit without checking on their rate of drainage. This would be true for tool packs such as ryobi and kobalt too, since they have internal BMS boards that are powered up from the cells for which they monitor. An EV can also have this problem but it may be lessened if the BMS is powered from the 12V starter battery, which would need to be kept on a trickle charge or it will sulfate and fail.
If you have something like a bench power supply or some sort of current regulated source, then you might be able to ‘bump’ charge it back up to 2.6 and your lithium chargers might decide to help again.
But the protection circuit may have the cell locked out. sometimes they can be charged back thru the body diode of one of the FETs in a tool pack.
[edit] this is a risky procedure and the cells could ignite when re-charged from such a low level.
