If you have a voltmeter:
Test voltage between B+ and B- with battery connected, disconnect the battery it and measure the battery voltage, if there is a large difference in value the board is loading down the battery and there is probably a short somewhere.
Put negative probe on a GND solder pad (that's ground) then check the 4.2V, 3.3V and +5V pads for voltage.
If you have access to an oscilloscope, using GND as ground reference probe the DAT for digital signals (data) and CLK for a clock signal. Any signals or voltages will indicate if the board is somewhat operating or completely dead.
Then if one has a working board you can measure different point between the boards. That is still guess work without a schematic but it might be worth a try.