I found an unmarked, cylindrical lipo cell in my box of cells. I can only assume it came out of a vape. My question is, if possible, how can I know if it can be charged to 4.3-4.35. Like, I know I can charge it to that state. But is there a way to know if it was designed for that? To my knowledge it’s tweaks to the chemistry that allow for the higher, voltage, correct? They aren’t just over charging a cell at the cost of cycle counts are they?
Hey Joe, <insert Hendrix lyrics….>
Cells have a nominal voltage which is normally a giveaway of its fully charged voltage but you are right, in that manufacturers dont simply “overcharge” a cell to give a higher voltage. Most lithium-ion cells will tolerate an overvoltage of about 0.1V in their fully charge state but it will adversely affect capacity and life cycle availability. Differing voltages are acheived/set by differences in chemistry and internal materials used, and not by simply forcing more juice in than they were designed for. Only “HIgh Voltage” LiPo/Li-ion cells have a fully charged voltage of 4.35
Give it a gentle charge (circa 250mA) upto 4.10V. If you have a way of measuring temperature reasonably accurately (cheap IR laser and some black electrical tape to take a reading off on the cell would be ok), that would be beneficial and make sure its not getting hot. Anything over about 40’C would be a worry.
Essentially, without having more information on the cell, it would be very difficult to see if it was (or not) designated a HV Lipo and its better to be safe than sorry!