Yamaha YFM660FS Grizzly 4x4 Supplementary Service Manual page 209

Charging method using a constant voltage charger
YES
Charge the battery until the charging
voltage reaches 15 V.
NOTE:
Set the charging time to a maxi-
mum of 20 hours.
Leave the battery unused for more than 30
minutes before measuring its open-circuit
voltage.
→
12.8 V Charging is complete.
→
12.0 ~ 12.7 V Recharging is required.
→
Under 12.0 V Replace the battery.
CAUTION:
Constant amperage chargers are
not suitable for charging MF bat-
teries.
CHECKING THE BATTERY
Measure the open-circuit
voltage prior to charging.
Connect a charger and
ammeter to the battery and
start charging.
Is the amperage higher
than the standard charging
amperage written on the
battery?
Voltmeter
3 - 62
CHK
ADJ
NOTE:
Leave the battery unused for
more than 30 minutes before
measuring its open-circuit voltage.
NO
This type of battery charger cannot
charge an MF battery. A variable
voltage charger is recommended.
Charger
Ammeter