GPD Win Max Repurpose Needs Help!

[Baregeek]

I have a personal project that I could use some help/guidance on.  GPD recently released an upgrade main board for the device so DIY folks can swap out the mainboard with the latest 11^th gen Intel CPU.  GPD even release CAD files for a case to repurpose the board.  I modified the CAD files so that they were more easily 3D printed, found a CPU cooler, I found a solution for the Wi-Fi antennas and am this close to getting the old board up as a full fledged mini PC.  One thing stands in my way.  The board will not boot without the original handheld battery connected!  It will run fine over USB type C PD, but you need to connect the battery to get it to boot.  This is all that is missing to repurpose what would otherwise be an unusable board.  I have contacted GPD and they don’t have a solution.  The original battery is much too large and not needed for a desktop type application.  I figure I could solve this in two ways:

 

1. Wire something to the battery connector so that it “detects” a battery and will boot correctly.
2. Wire a much smaller battery internal to the device that would both satisfy the battery check on boot and could have the added benefit of holding the time when powered off.

 

Both of these options seem possible, but I don’t have enough experience with battery engineering to work through what is needed.  I don’t want to blow up a battery or burn out the board.  Please help!