I have 3.7V 4000mAh Li-ion battery.
I also have 0-30V/6A power supply which can limit output current. Provided that I charge the battery with voltage limited to 4.2V, I can change the maximum current output of the power supply.
Let's say that have set these parameters on the PSU
-voltage limit = 4.2V
-current limit = 500mA
On the powerIf current is higher than 500mA, then the voltage will drop to a value where the current is 500mA.
Assuming the battery is @5%, I can set the current limit to 4A and charge the battery less than 1 hour.
My questions are >
What is the optimal charging speed at which the battery will be safely charged?
What is the fastest charging speed (safe charge)?
What is the fastest charging speed (unsafe charge)?
unsafe= can damage battery life or charging cycles
Temperature may and may not be considered in the answer.