Canon WFT-R10A Wireless File Transmitter for EOS R5 C & R5 Mirrorless Camera - Manual (Page 20)

(4) Battery release lever
To remove the batteries, release (3) and pull (4) in the direction of the
arrow.
Caution
When only one battery is used, inserting it on the camera side will
power only the camera. Inserting it on the transmitter side will not
power the camera or the transmitter.
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