All I know is what the Manual says, maybe yours was changed by a previous owner.
The auxiliary battery is located behind the passenger access door behind the rear wheel, (see Picture B-P46). Under heavy use it is recommended to check once a month, see maintenance section.
In order to access the auxiliary battery one must do the following:
1. Unscrew wing bolt, (see Picture B-P50).
2. Pull down on release handle above the exhaust pipe, (see Picture B-P51).
3. Lift barrel bolt.
4. Slide out battery tray.
CAUTION: DO NOT ATTEMPT TO REMOVE BATTERY COVER WHILE ENGINE IS RUNNING / EXHAUST IS HOT. HOT EXHAUST CAN cause SEVERE BURNS.
To reinstall reverse steps above. (Ensure cover is engaged with flange above battery).