Can you use the m1 MacBook Pro with the battery disconnected?

I don't think any one has experimented doing that.

What I can tell you is with the Intel models the SMC services which monitors your hardware for problems and manage the thermals have issues when you disconnect the battery. Between the loss of the battery thermal and voltage inputs your SMC will place the system into CPU Safe mode which ramps up the fans and lowers the CPU's clocking. And you can't over-ride it!

Now when we work on fixing the logic board on our desk this is not an issue as it won't affect the diagnostic process of tracing the power rails or checking the signals. It's only an issue if you are trying to use the system.

Now you also introduce a new problem as without the battery your data can get corrupted! With the newer MacBook Pro's with soldered drives (flash) that could lead to a logic board failure! As all it takes is a loss of the power adapters power.

So you would be playing Russian Roulette which as you know watching the movie The Deer Hunter it's a dangerous game!