The Canon Compact Battery Pack CP-E4 is a high-capacity, heavy-duty, yet compact power source for compatible Canon Speedlites – it helps to deliver faster recycling times and more flashes between battery changes. The CP-E4 pack is powered by eight AA batteries via the supplied CPM-E4 battery magazine and attaches to the flashgun via a cable. For control functions, you'll still need to have a separate set of batteries in the flashgun as well. When the 580EX/EXII is in its default mode it will draw power from both sets of batteries, but in order to save battery power within the flash unit you can use the 580EX/EXII's Custom Function 12 to ensure you only draw power from the CP-E4 battery pack. This preserves a fully charged set of batteries in the flashgun in case the power from the CP-E4 battery pack starts to run low.

Compatible with the following Canon flash units:

580 EX / 580 EX II / MR-14EX / MT-14EX