The IC I am using is: STNS01. As I read, charging Lithium ion cells consists of three phases:
Precharge ("conditioning" on other articles) phase -> Approximately 10% or 20% of fast charge current (Constant current phase). A Precharge timer is used here apparently. When this timer times out,(30 mins for STNS01) charging is stopped.
Constant current phase -> Happens when Vbat is between 3v and 4.2v. Constant current is applied while voltage rises until ~4.2v. Apparently, this charges the cell to approximate 70% full.
Constant voltage phase -> Constant (4.2v) voltage is maintained while charging current dies down (phase terminated when charging current reaches some low threshold).
- When this precharge timer times out, does this indicate a faulty lithium ion cell?
- I understand that in the first place, lithium ion cells shouldn't be discharged to below cutoff to prevent damage (2.6-3.0v for most Li-ion). Is this correct?
- If statement 2. is correct, does this mean that "deeply" discharged batteries (Li-ion cells discharged all the way to 0v) are not always successfully charged by STNS01 (or similar charging ICs)?
- If this timer timed-out, is better to assume the battery is damaged or can we restart the entire charging cycle to try to recharge the battery again (ie., restart the 30 min timer)?