Without any circuit, the 18650 lithium battery has the same voltage as the smartphone battery and can be directly connected to the mobile phone. It's just that the smartphone has some protection, so just remove the battery protection board from the smartphone and install it on the 18650. The size and installation method are big problems, because it doesn't fit in a smartphone.
Can any master make a circuit for 18650 lithium battery so that 18650 battery can reach the current
Introduction Can any master make a circuit for 18650 lithium battery so that 18650 battery can reach the current and voltage of smartphone battery without any circuit, 18650 lithium battery and smartphone?