Honda TRX500FM6 Owner's Manual page 203

Battery
Battery Charging
Refer to Safety Precautions on page 115.
(1)
(1) charger
Be sure to read the information that came with your battery charger
and follow the instructions on the battery. Improper charging may
damage the battery.
We recommend using a charger (1) designed specifically for your
Honda, which can be purchased from your dealer. These units can
be left connected for long periods without risking damage to the
battery. However, do not intentionally leave the charger connected
longer than the time period recommended in the charger's
instructions. Avoid using an automotive-type battery charger. An
automotive charger can overheat an ATV battery and cause
premature damage.
Servicing Your Honda 193