Honda TRX500FM Owner's Manual page 50

Controls & Features
Be sure the engine is on and the headlights are turned off before using
the accessory socket, otherwise you may drain the battery.
The accessory socket's rated capacity is DC 12V, 120 Watts (10A) or
less. If you exceed this limit, you may blow a fuse. See If a Fuse Blows,
page 192 .
When you are done using an accessory, unplug it, and cover the socket
with the cap.
Be careful not to flood this accessory socket when washing your ATV.
Instruments & Controls 41