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Power draw on alexa classic? Figuring out how many batteries to get.


Berry Spinx

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Tvlogic 058 and nucleus follow focus are the accessories that I'd attach to the alexa classic. I've heard that 98wh gives 20 minutes, 130wh gives 1.5h and 250+wh gives 3+ hours but these are from a youtube video and most likely without accessories. 

Can anyone chime in?

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15 minutes ago, Berry Spinx said:

Tvlogic 058 and nucleus follow focus are the accessories that I'd attach to the alexa classic. I've heard that 98wh gives 20 minutes, 130wh gives 1.5h and 250+wh gives 3+ hours but these are from a youtube video and most likely without accessories. 

Can anyone chime in?

If 98WH gives only 20 mins .. how does 130WH give 1.5hrs ?...    something wrong there I think .. 

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https://cinematography.com/index.php?/topic/76590-alexa-power-draw-values-whilst-in-standby-mode/

Roughly 100W for the camera, 10W for the monitor, don’t know that follow focus, but a quick google suggests maybe 20W when the motor is running.

So 130 Wh would probably last about an hour.

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The Alexa classic is a thirsty beast and I have shot a bunch of B-Roll stuff with it to ProRes internal and ArriRaw with an Odyssey7Q and to SxS cards with just the EVF mostly using Anton 120Wh batteries and I don't think I ever got more than an hour from a battery.

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  • 1 month later...

To what extent are more expensive batteries better than less expensive ones? (Other than durability.)

I have a Watson battery that powers an Alexa Classic fine, but not for long. Then again, it seems none of the 150 WH batteries last that long...

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3 hours ago, M Joel W said:

To what extent are more expensive batteries better than less expensive ones? (Other than durability.)

Generally, the more expensive batteries can handle a higher power draw for sustained periods. You want high amperage batteries with LED lights, high-bright monitors, and power hungry cameras like the Alexa. 

Cheaper batteries with a similar watt-hour capacity but lower amperage rating will stop working much sooner when they are no longer fully charged. Especially when you are powering additional accessories from the same battery.

In those cases, you’ll notice the camera/monitor/lights powering off randomly and possibly corrupting your footage or damaging the device, even though battery still has a few bars on it. This will also shorten the life of your battery. 

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1 hour ago, Satsuki Murashige said:

Generally, the more expensive batteries can handle a higher power draw for sustained periods. You want high amperage batteries with LED lights, high-bright monitors, and power hungry cameras like the Alexa. 

Cheaper batteries with a similar watt-hour capacity but lower amperage rating will stop working much sooner when they are no longer fully charged. Especially when you are powering additional accessories from the same battery.

In those cases, you’ll notice the camera/monitor/lights powering off randomly and possibly corrupting your footage or damaging the device, even though battery still has a few bars on it. This will also shorten the life of your battery. 

Thanks, that's sort of what I feared. This battery is rated for 12A but the camera shut off with two bars remaining if I remember correctly, after which the battery read as empty. With a Gemini 4:4:4, I assume this will only get worse. Or it could have been a fluke.

Are there affordable (and good) high capacity AB mount batteries out there? The 90Wh Anton Bauers seem widely available used, but I'm not sure how much sense buying like ten of them makes.

Your post might speak to Berry's original question and the subsequent debate about the apparently non-linear correlation between Wh and battery duration.

If there's a non-zero floor below which the camera won't operate, perhaps higher-capacity batteries do last longer (particularly lower quality ones) and it would make sense to own fewer high capacity batteries rather than more low-capacity batteries for high-draw devices.

If so, yet another point for the Amira.... 

Edited by M Joel W
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13 minutes ago, M Joel W said:

Are there affordable (and good) high capacity AB mount batteries out there? The 90Wh Anton Bauers seem widely available used, but I'm not sure how much sense buying like ten of them makes.

I’ve had good luck with Anton Bauer HCX batteries with the Alexa Classic/Plus in the past. Can’t speak to the current AB models. I would avoid 90wH batteries unless you fly with your camera package all the time, you’ll be swapping every 30min. 

I’ve noticed my local rental houses like the Core SWX Hypercores. I personally own BlockBattery 2F1 14/28v switchable batteries since I have both 24v and 12v cameras. They’re pretty affordable and based in SoCal, great customer service. 

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Wanted to add, the battery voltage is a better indicator than the battery’s LED indicator bars of when your camera is about to shut down. Most camera manuals specify the minimum operating voltage and will allow you to set a warning when the voltage drops below a certain threshold.

When I was AC’ing I used to change Alexa batteries around 12.3-12.5v if I had to make them last. That is cutting it kinda close, as the voltage drops very quickly when below 12.0v. Other ACs would always change once the camera dropped below 12.9v to be safe.

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Thanks, that's really helpful to know. At some point I think I learned that but totally forgot! 

Separate question, but this seems like the right thread: is the base of the Alexa Classic the same as Sony VCT? Arri has these $900 or $1400 tripod plates and I'm wondering if I can just get a $300 Sony plate (or $150 Small Rig plate) instead.

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1 hour ago, M Joel W said:

Thanks, that's really helpful to know. At some point I think I learned that but totally forgot! 

Separate question, but this seems like the right thread: is the base of the Alexa Classic the same as Sony VCT? Arri has these $900 or $1400 tripod plates and I'm wondering if I can just get a $300 Sony plate (or $150 Small Rig plate) instead.

Well, please take it with a grain of salt because I haven’t worked with a Classic/Plus/XT in a while! If work with an ARRI these days it’s always a Mini. 

As I recall, the base needs an Alexa specific riser to get to either Studio or VCT, but I could be wrong.

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6 hours ago, Satsuki Murashige said:

Well, please take it with a grain of salt because I haven’t worked with a Classic/Plus/XT in a while! If work with an ARRI these days it’s always a Mini. 

As I recall, the base needs an Alexa specific riser to get to either Studio or VCT, but I could be wrong.

Thanks, I was forgetting a little adapter to connect to VCT. That sounds right.

Do you know if the Mini and Amira have better highlight detail than the Classic/Plus? Arri originally quoted +7.3 stops over 18% gray for ALEV III and now quotes +7.8. And I believe they changed sensor vendors:

https://www.arri.com/en/learn-help/technology/image-processing

But they also changed firmware a few times. And does ArriRAW have more highlight detail still? 

It's an interesting question (to me, a nerd, at least) what Arri will do with their new 4K+ S35 sensor. Dynamic range over 18% gray at a given ISO should be a product of full well capacity. A 4k sensor should have roughly twice as many pixels as a 2.8k sensor (and half the full well capacity) and a 5.7k "true 4k" sensor roughly four times as many (and one quarter the full well capacity) at a given ISO. So Arri should lose a stop or two of highlight dynamic range with their new camera if it stays at base 800 ISO.

I'm pretty sure Red Helium, for instance, has a stop less highlight detail at a given ISO than the Dragon, and of course both have less than the Alexa.

It'll be interesting to see if Arri works magic or if the new Alexa is 3200 Base ISO or something. 

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1 hour ago, M Joel W said:

Do you know if the Mini and Amira have better highlight detail than the Classic/Plus?

And does ArriRAW have more highlight detail still? 

Sorry, don’t know but it seems comparable to me. 

I don’t shoot ARRIRaw, so again no idea. I would imagine so without the highlight compression being applied. I’m sure others will chime in to confirm or deny!

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  • 4 weeks later...

Thanks again everyone. One last question (not just about Arri, but also Aaton batteries): how do I store these so they last, and what batteries can be re-celled and which can't? 

I don't shoot much, I have nothing lined up right now for either camera, but I like owning my own gear because I'm a tinkerer. I had a Ronin a few years back and sat on discharged batteries and they died.

How do I keep my AB mount and Aaton batteries lasting a long time while in storage? Thanks.

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There should be maintenance guidelines for your battery model on the manufacturer’s website or in the packaging. Usually, with lithium batteries you’re supposed to charge them up every month or so they maintain full charge capacity. I’d check to see if there’s anything specific you should be doing.

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Thanks, I appreciate it. I think I'll own fewer batteries and rent more when I need them.

Got a steal on Hypercores from B&H but might return them unopened as it looks like I won't be shooting as much as I planned to. 

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On 1/2/2021 at 4:50 PM, M Joel W said:

Thanks again everyone. One last question (not just about Arri, but also Aaton batteries): how do I store these so they last, and what batteries can be re-celled and which can't? 

I don't shoot much, I have nothing lined up right now for either camera, but I like owning my own gear because I'm a tinkerer. I had a Ronin a few years back and sat on discharged batteries and they died.

How do I keep my AB mount and Aaton batteries lasting a long time while in storage? Thanks.

Different battery chemistries require different storage and maintenance routines to get the most life out of them. So it depends what sort of batteries you are using.

Lead acid cells for example, which you might find in big block batteries, should be stored fully charged, and cycled every 6 months.

Ni-Cads are better stored discharged, or only partially charged, with a cycle at least once a year. 

NiMH cells can be stored either charged or discharged, with a yearly cycle.

Lithium Ion batteries are best stored at about a half charge, and will last longer if not run all the way down when used.

Individual batteries may have specific requirements so always defer to the manufacturers recommendations.

In all cases, avoid storing batteries in high temperatures. For more in-depth info, I often visit the Battery University website, very informative.

You can usually re-cell any battery except “smart” batteries. The main advantage of smart batteries is therefore to help the manufacturer’s bottom line. 

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