From The Currie Tech Dealer Wiki
Tricruiser (STB 36V) Battery Pack
Testing equipment required:
Battery voltage check
When fully charged, the Tricruiser battery pack should measure at about 38-39 volts. Immediately after charging, the voltage reading may be higher; let the battery sit off the charger for about 15 minutes before taking a voltage reading. Failure of the battery to charge to the expected maximum voltage may indicate that the pack has reached the end of its useful life.
Check battery voltage between charger port pins with probes. Be careful not to cause a short. Note that the top "horizontal" pin is inactive when the battery power switch is OFF, and positive (+) when the battery power switch is ON.
A fully charged battery should read about 38VDC
If, with the battery turned on, you do not get a voltage reading between the top horizontal pin and the left vertical pin, you should check the battery's internal wiring and switch for proper operation.