Here is a little modification I made to my sled to better power the ALEXA. It works like a charm so I thought I'd share:
Been flying the same setup for the past 3 years; ALEXA with Cooke lenses (5i's), cinetape, teradek, 2 motor preston with MDR2 on my HD PRO GPI sled.
To keep the post short, I fly 1 Dionic HD in the front (below the post) and 2 Dionic HC at the rear : I have been using the 2 rear batteries in 24V mode to power the ALEXA until last week.
The 2 HC's at the rear would drain very fast feeding the ALEXA ; I needed at least 8 of them to get thru morning. Since the sled is very well balanced the way it is right now, I considered using the front battery in 14V mode to feed the camera. The big Dionic HD battery in front is from the rental house and we already use them in studio and handheld mode.
Since the 3 jumper blocks from PRO are not designed to feed the camera from the front plate, I called David Hable and he re-wired one of my blocks to do just that : front is now camera only, and the 2 rear plates are ACC and MONITOR only (see pic).
At the same time , he also re-wired one of my Arri power cable to feed the camera in 14V instead of 24V. Only thing to remember if going with this mod is to go into the ALEXA menu and change the "low battery" warning on the BAT1 position to somewhere around 11v instead of 22V: if not, the camera will "think" the voltage is way too low to power the camera.
The mod is simple and cheap(re-wiring a jumper block and a power cable) and the difference is huge in power management: not only am I saving my batteries (using the rental house instead), the camera will last almost 70 minutes on one single fully charged Dionic HD .
On paper it seemed like a win-win modification and I can now confirm it works great with this setup.
Would love to see if people here have made such modifications and what they did.