2. External Power Sources
Speedlite 550EX can use any of the following two external power sources.
For details, refer to the Instructions of the respective external power source.
(1) Transistor Pack E
Uses Canon Battery Magazine TP (six size-C alkaline batteries) or Ni-Cd
Pack TP.
(2) Compact Battery Pack CP-E2
Uses six size-AA alkaline or nickel-hydride batteries.
Size-AA lithium batteries can also be used.

Recharging Time and Available Flashes

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•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 touch the plug.
•Even when an external power source is used, batteries must be installed in the 550EX
to power the internal circuitry.
•The 550EX uses both the internal and external power sources to recharge the flash.
Therefore, the internal power source may become exhausted sooner than the external
power source. For prolonged flash photography, keep a spare set of batteries handy
for the internal power source.
Internal
Power
Sources
External
Power
Sources
Power Source Recharging Time (sec.) Available Flashes
Quick Flash Normal Flash
Size-AA alkaline batteries ×4 Approx. 0.1 - 4 Approx. 0.1 - 8 Approx. 100 - 700
Transistor Pack E (Ni-Cd Pack TP) Approx. 0.1 - 1.5 Approx. 0.1 - 3
Approx. 300 - 1800
Transistor Pack E Approx. 0.1 - 2 Approx. 0.1 - 5
Approx. 350 - 2200
(Size-C alkaline batteries)
Compact Battery Pack CP-E2 Approx. 0.1 - 1.5 Approx. 0.1 - 5
Approx. 350 - 2200
(Size-AA alkaline batteries)
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