Powering an Alexa

[Eric Fletcher S.O.C.]

You could be in trouble with a single Dionic 90, even if it's only powering the camera body and recording to SxS. The specs say 85W with camera body, viewfinder and SxS recording. So...maybe 80w without the viewfinder?

 

In a nutshell, you not only risk short runtimes, but you can damage your battery and reduce its overall service life. John Ritter can confirm this. Essentially, the Dionic90 were designed for a maximum sustained current load of 50W. AB stated that they could handle up to 90W with reduced service life (which means your batteries will wear out far sooner than the normal 3 years).

 

 

Hold on there for a second tex. That info is flat out wrong.

 

A dionic 90 is good for.... Wait for it.... 90watts, not 50, that's a hytron 50 a VERY different battery. The Dionic HC is closer to 100watts but can pass closer to 200watts draw thanks to different cells and a different protection board.

 

As for the Alexa's draw I've measured mine at 72watts in the config that I'm flying it on my show Which you can read about here

 

As for damaging the dionic, it's not keeping them on charge or pulling over 100watts and causing high internal temps, pulling rated load will not short life them. That info is from Paul Dudeck who knows more about his batteries than John Ritter

 

Just needed to clarify this info

[James Davis]

Also probably worth double checking two things:

 

1. Always ask are they going to be using a codex or are they shooting straight to SXS cards

 

2. Ask for details of the rental house, call them up and check that they can provide a "steadicam plate" to bridge the gap across the shoulder cutout, if you don't have the time/money to buy one

(as made by people like Matthias, Baer Bel and Optical Support), then this is your next best option.

These plates are essential if you want to avoid potential vibration coming through the camera.

So if you are doing it through the rental house, after checking that they have it I would then ask them to hold it and speak to the production manager/producer (depending on the scale of this job) requesting that they ask the rental house for this plate, emphasizing that this is essential for mounting to steadicam and you cannot mount the camera without it.

This way you leave the responsibility in their hands/the rental house's hands if for whatever reason (worst case scenario) it doesn't turn up.

 

In addition to this a Clip on matte-box is always a good idea, if you haven't requested one already.

 

Plus, If you have a set of Torx drivers handy the fixed protruding viewfinder mount makes a great place to mount a single follow focus motor with a 45degree motor bracket, once you disassemble it and remove the sliding sleeve.

 

For now I would just put a battery on the back of the camera and use your sled batteries to power all your accessories/monitor etc, it's the simplest route to take and will be the least "incident prone" way to deal with things on the day, the last thing you want to do is cause any issues with your batteries if you are even a little unsure of their ability to cope.

Edited August 21, 2012 by James Davis

[Mark Schlicher]

Paul can you weigh in on these points?

 

I'm going off of published specs for the Dionic 90 (not the Hytron 50, I know the difference, thank you) and phone conversations with AB tech reps (not Paul) as well as conversations with John Ritter.

 

I guess I'll go pull the manuals them out and quote them, not that it will do any good.

 

The name is Mark, not "tex." You can disagree without being disagreeable. Or maybe you can't.

 

The 72W real-world power draw is useful information, less than the spec I'd read from Arri (Alexa Manual 4.0, page 20).

[Mark Schlicher]

Anton Bauer Dionic 90 manual Rev "U" page 5:

 

"Recommended operation: 15-50 watts*"

"(Maximum Discharge rate) 90 watts"

 

(footnote): "*Routine use of a battery at discharge rates greater than the recommended operating range can reduce overall service life."

[Mark Schlicher]

Dionic HC manual Rev B page 14:

 

Recommended operation 50-100 watts

Maximum discharge rate 150 watts

Fuse internal 10A

 

footnote: Routine use of a battery yada yada...

 

The discharge rate specs for the Dionic HCx (manual Rev A page 17) are the same as for the HC above. The capacity is higher.

 

It's worthwhile to distinguish between capacity (93Wh "nominal" for the Dionic 90, 91 Wh "typical" for the Dionic HC) on the one hand, and recommended/maximum discharge rate (50/90 for the Dionic 90, 100/150 for the Dionic HC) on the other hand. You could say that, roughly, that Dionic 90s were designed for two hours at 50 watts recommended load, where the Dionic HC is designed to last one hour at 100 watts recommended load.

 

I've corresponded and spoken by phone with Mike Pedevillano (Customer Support Supervisor) and others from AB about this, and am passing along my understanding of what they recommend and why. If Paul Dudek has other information, I'm eager for the clarification.

[Eric Fletcher S.O.C.]

Mark,

 

That reduced life is for draws over 90watts. If 90 watts was the true limit the thermal fuse would kick at 95watts not the 144watts that it does protect at.

 

I don't know why Sony would be rating The Arri Alexa's power draw.

 

As for obtaining tech info on these batteries and understanding them, I'm doing pretty good in that department since I am testing batteries for Anton Bauer this season on my show. Quote the manual all you want, but please understand what you're quoting

[Mark Schlicher]

I've corrected my "Sony" mistype, apparently after you'd read my post. However, it matters not to the substance of what is being discussed.

 

I do understand what I'm quoting, hoss.

 

You say:

 

"That reduced life is for draws over 90watts."

 

Anton Bauer manual for Dionic 90 says:

 

"Recommended operation: 15-50 watts*"

 

(footnote): "*Routine use of a battery at discharge rates greater than the recommended operating range can reduce overall service life."

 

It is precisely this question that caused me to call AB and ask myself. Mike P confirmed this.

 

Dionic 90's can run over the recommended current draw before popping the thermal fuse, but they do not recommend it. The reason they don't recommend it is that it reduces the overall service life of the battery.

 

The Dionic 90 is listed as having an 8A fuse (115W@14.4v) not a 10A (144W). Nevertheless, they are fused for the maximum, not the recommended current draw. Running above recommended is not good for any battery's longterm health, whether it blows the fuse or not.

 

Again,

 

There's a difference between capacity (93Wh "nominal" for the Dionic 90, 91 Wh "typical" for the Dionic HC) on the one hand, and recommended/maximum discharge rate (50/90 for the Dionic 90, 100/150 for the Dionic HC) on the other hand.

 

You could say that, roughly, that Dionic 90s were designed for two hours at 50 watts recommended load, where the Dionic HC is designed to last one hour at 100 watts recommended load.

 

If Anton Bauer is telling you something different than they are telling the rest of us, please share in detail.

[Mark Schlicher]

Sigh. We all pretty much saw this coming, didn't we...

[William Demeritt]

Sigh. We all pretty much saw this coming, didn't we...

 

Finding our way into a single technical aspect of the original topic that reveals people's personal approaches to equipment? Yea, I logged in, so I knew what I was getting into...

 

"Reduced life" meaning what, exactly? 120 cycles instead of 150? 180? How greatly reduced?

 

In my opinion, the manuals reflect the engineer's specifications tempered with legal department's "we gotta protect ourselves against the warranty". As you quoted, the Anton Bauer manual says "recommended operation" is 15-50 watts. The 8A fuse protects against an overdraw of 115W, so why is the recommended operating range less than 50% of the fault protection? Probably because when they first started making Dionics, they don't want people calling, saying "These batteries suck: I ran a 90 watt load every day, and the batteries only lasted 110-130 cycles."

 

Mark, as you said: "Dionic 90's can run over the recommended current draw before popping the thermal fuse, but they do not recommend it. The reason they don't recommend it is that it reduces the overall service life of the battery."

 

OK, duly noted. If it's my batteries, I'll probably be more conservative with what they power and how I configure my setup. If the rental house rents me a camera that sucks down 85 watts (14.4V means 5.902777... amps) and sends Dionic 90's, then I'll defer to how they rent their camera package. However, I don't think I'll be too worried when the battery with an 8A fuse and recommended load of 15-50 watts has to run an 85 watt camera at 5.9-7.0 amps.

 

Perhaps it's just my approach to gear, but recommended is a safety net, maximum is a MAXIMUM, and if we're operating with some wiggle room, I'm not incredibly worried. As far as I can tell, "recommended" here is strictly regarding service life. If we had evidence the "recommended load" was because of discharge characteristics changing, overheating as amperage increased, etc., perhaps we should be worried.

 

As long as they make it through my shoot, I'll do as the rental house or camera provider wants. In the mean time, I own Dionic HC's and I love them. I'd ask for them, but we don't always get what we want.

[David M. Aronson]

Thanks for all the help guys. Next question, this one for master series owners. Production want the lens hight as high as possible. Can a Master Series sled with stock wiring handle the draw of an alexa and arri FF if I stick the 160s on the bottom?

Edit: Also, they only have 160s.

[Brian Freesh]

Why does everyone care this much about the detailed specifics of the performance of a Dionic 90? It's got a 90 watt hour capacity, it won't last forever. Done.

 

For those who missed it, the Dionic 90s are David's. Mark's concern was that David could be shortening the life of his own batteries if used to power the Alexa. The 160s belong to the camera owner, who apparently is not a rental house.

 

Mark didn't say not to do it, just gave David a heads up that it could wear out the batteries faster. How much faster is a great question, Will. And I imagine the occasional job with the batteries maxed out won't be a significant issue. But as with any machine/device/electronics, if constantly pushed to its limits, it will wear out faster. Regardless of the specs, 100% is more than 90% is more than 50%, etc.... Doesn't matter what the manual says, or who's testing batteries. Who cares?

 

David, don't try to power the camera through the rig, figure that out later. For now, throw a 160 on the bottom, power the camera with your 90s, have a great time. At the end of the day see what you liked and disliked about the set-up and adjust accordingly for the next time. Heck, adjust during the day if you have the means and the time. Maybe the camera will be lighter than you like, or heavier. Or maybe you'll want a longer post next time, etc...

[David M. Aronson]

Thank you Brian. What's the reasoning behind not running power through the rig though? Just for less hassle or will it break my rig?

[Brian Freesh]

Because it was already mentioned it wouldn't work, from a former master series owner:

 

Yup, that 24V converter on the old Master Series sleds won't be able to give the Alexa what it needs in terms of power. Quite frankly, it won't be able to give a lot of cameras what they need in terms of power. When you get some time, I'd recommend changing that out for a 2nd battery plate so you can have true 24V, rather than upconverted 24V. For this upcoming shoot, you might have to live with a battery on board. Dionic 160 isn't small. If you can get some Dionic HC's you'd be in much better shape, otherwise the camera will get heavy on you very quickly.

[David M. Aronson]

Even if I run 12V through the rig and skip the down converter? It's filming a tour of some battle ground in as close to one take as possible, so having less weight and thus, less batteries is a good thing. I want to be 100% that I have to throw a couple of extra pounds on.

[Brian Freesh]

You'd need a new power cable, the one you have is wired to the 24v pin on the sled. I'm sure Terry West or Chris Konash could make one for you.

 

I've no idea what the wiring inside that sled is like, so no idea if it can handle the current draw. Someone at Tiffen could answer that for you.

 

The 1.8lb 90 isn't gonna kill ya, that's why I said to use that instead of the twice-as-heavy 160. Use the 160 if you want to save your batts.