Continuing my current fascination with batteries for external flashes, it was only natural to try an external battery pack. In addition to recharging the flash more quickly, an external battery pack provides more flashes without changing the batteries. After a bit of browsing and reading in POTN, I decided on the 3rd party Pixel TD-381 rather than the more expensive Canon CP-E4. I was especially curious as to how an external battery pack would compare to the rapid recharge from NiZn batteries.
Whereas the NiZn batteries will fit into any flash that uses standard AA batteries, an external battery pack requires a special connection on the flash. Not all flashes have this special connection but my Canon 580 EX II has it. My old Nikon SB-24s also have a connection for external batteries but, of course, the Canon and Nikon connections are different. I decided to order the version for the Canon and also decided to order from a US supplier, Cheetah Stand, instead of an eBay supplier -- just in case something went wrong.
As shown above, the TD-381 is a hard plastic case with connection cable and a cloth carrying case. The carrying case has a belt loop; the cable is long enough to reach the flash when the TD-381 is belt mounted. The plastic case has a hole through it so that it can be attached to the bottom of the camera; a thumb screw is included.
The TD-381 holds eight AA batteries that are wired into a “dual circuit” charging system. The batteries are in a tray that is removed for changing batteries. I'd read of problems with flimsy latches and loose battery connections but mine seemed fine. The tray can only be installed in the proper orientation.
So, how well does it work? I installed eight freshly charged NiMh AA cells and tested the TD-381 in the same manner as I did the NiZn batteries. That is, I fired off five shots as quickly as the 580EX would indicate it was charged. In previous tests, the 580EX with NiMh batteries could get off five shots in 15.7 seconds or 8.1 seconds using NiZn batteriers. With the TD-381, I could get of five shots in 5.9 seconds. Naturally, I couldn't resist putting the NiZn batteries into the TD-381. Using NiZn batteries in the TD-381, the time required for five flashes was reduced to only 5.5 seconds!
Repeating my warning: Be patient and don't fire off many shots in a short time because the flash may overheat!
I normally have no need for rapid fire flash or even for hundreds of flashes in event photography but now have the equipment to do so. My plan is to use the NiZn batteries installed in the 580EX for normal use and, when necessary, use the NiMh batteries in the TD-381.