2005 Kawasaki KAF400 Mule 600 and Mule 610 4x4 Service Manual, Page 348Get this manual
16-18 ELECTRICAL SYSTEM Battery
Initial Charging
WARNING
Keep the battery away from sparks and open flames during charging, since the battery gives off an explosive gas mixture of hydrogen and oxygenWhen using battery charger, connect the battery to the charger before turning on the chargerThis procedure prevents sparks at the battery terminals which could ignite any battery gases
CAUTION