I assume that universal chargers should not be used for activating overdischarged LiIon cells. Is this assumption correct? My theory is that such a charger would read the low voltage and assume NiMh, pushing high current into the cell and that’s not recommended.
The nitecore I4 & D4 do this correctly.
How do they detect a LiIon cell? This is the interesting part.
AFAIK, if the voltage is very low, they assume it is a LiIon cell & charge it at a very low rate & monitor it (ie: they don't assume it is Ni-MH battery).
Btw, HKJ is our go-to expert on these matters.
Right, HJK could possibly have insights on this. Anyway, checking with voltage doesn’t really make sense, 0.8V is a valid discharge voltage for a NiMh cell and you want full current applied there, but for a LiIon, anything lower than around 2.8V (not sure on the exact value, lower than 3V, over 2.5V?) would be the point where a charger has to do slow charging with a very low current (under 100mA).
Usual LiIon cells will jump above 2 volt when charge current is applied and 2 volt is the common changeover point between NiMH and LiIon in chargers.