Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 52)

Charging the Battery
1.
Connect and plug in the battery charger.
Connect the power cord to the charger and plug the other end into a
power outlet.
All indicator lamps are off when no batteries are loaded.
2.
Remove the protective cover.
Remove the included protective covers from the charger and battery.
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