The battery and accelerometer boards came in at the same time. The accelerometer worked, the battery, not so much.
The first problem is that fitting a 20mm coin cell into a square inch with headers on each side is a loosing battle. My idea was to drop the front six pins to allow entry and to angle the holder so the battery would not short out on the back header.
The main board requires insulation such as electrical tape to keep from shorting the bottom of the front bus pins on the battery holder. Minor issue. I also somehow managed to get the battery backward in the schematic, requiring some trace cutting and bodge wire. The good news is that per the whole KISS principle, I'm only out $5 in PCB and an hour of screwing around trying to figure out why ground and VCC were shorted even after I cut the traces (its the vias, dumbass).
Next up? RTC or pressure.