I have a set of devices using Li-Ion batteries and featuring a charging IC (LTH7). Charging works normally on recent batteries, but does not on used ones.
Knowing that chargers initially try to maintain a constant current (CC phase), I was assuming to have a very low or no charging current for those used batteries, and thus expecting the charger to respond like if no battery were connected: increasing Vbat until the max value (4.2V).
Instead of that, I observe that Vbat remains constant around 0.1V. Any idea why the charging IC does not increase the battery voltage ?