Well, you could probably get a EC CCD if you wished.
The Embedded Controller (EC) is a very small ARM chip that controls all sorts of things, one being the boot up procedure. The EC runs even if you have powered off the laptop, but have the PSU still plugged in.
So, if you cannot boot the mainboard, you will still be able to talk to the EC and collect useful information. For example, the EC has a “battery” command that reads the values stored in the BMS via SMBus. You can get this information even with the laptop powered off.