Hi, there is the only way to supply power to the battery's contacts on the board from a laboratory power supply by connecting the appropriate contacts and applying voltage 3.8V.
BTW, one guy did the same thing that you want but using another battery as a power supplier, we wrote about it https://vrm24.com/blog/is-it-possible-to-make-the-htc-desire-s-smartphone-work-from-the-mains-without-a-battery
Hoosein Kruger
2021-11-07Thu Ra
2023-07-02