The Speedlite 550Ex can use any of the following two external power sources. For details, refer to the instructions of the respective external power source.
Transistor Pack E
Uses Canon Battery Magazine TP (six size-C alkaline batteries) or Ni-Cd Pack TP
Compact Battery Pack CP-E2
Uses six size-AA alkaline or nickel-hydride batteries, lithium batteries can also be used.
- While High-voltage Pack E315's main switch is still on, do not clean the connector plug with water or a metal pin and do not tough the plug
- Even when the external power source is used, batteries must be installed in the 550EX' to power the circuitry
- The 550EX uses the and external power sources to recharge the flash. Therefore the power source may become exhausted sooner that the external power source. For prolonged flash photography, keep a speare set of batteries handy for the power source.