@jmelson,
Not sure if looking at the same Encoder (a bit new to this...). From my analysis, Bit 5 corresponds to presence ('0') or absence ('1') of Battery Voltage. Nominal Voltage is 6VDC according to documentation, the Switching Point seems to be at ~4.7VDC.
Regarding the Checksum or other Integrity indicator - do you have anything regarding CRC with such Encoders?
Thanks, Alon Harpaz