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Callum Ross Thomson

Battery help for Arri 2c crystal motor

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I have recently ordered a CP crystal 24fps motor for my new (or should I say old) 2c.
In my hunt for a battery locally, and it's been suggested to me by a hobby store that

I could use a 14.8v LiPo battery as they're much smaller, lighter, run at a more constant

speed and hold much more power than the NiMH batteries that most people seem to

use with their arri motors.


I was originally told by the seller that this motor needs 16-18v, that if I use 12v it

won't maintain crystal sync speed. My understanding from reading on this forum

is that pretty much all constant speed 2c motors actually only need 12v, but if you

use a 12v battery the voltage can/will drop below 12v occassionally, so you need

a battery higher than 12v as a sort of safety net.


I haven't been able to get in contact with the seller of the motor since i've made the

purchase, so my question for you bright folk here is: do you think a 14.8v would allow

enough of a margin to maintain crystal sync speed for this motor?

Thanks in advance for any help!


Edited by Callum Ross Thomson

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Are you sure this motor requires 16-18V ?

If the power connector is a 4-pin XLR, there are good chances the motor requires 12V only.

In that case a 14.8V battery should work fine.

You'll probably need a capacity of at least 5A to get a decent running time.



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Thanks Jean, I hoped that was the case. That's the thing, the seller said it needed 16-18v, but maybe he meant

to imply that it just can't run on 12v. I've gone ahead with the 14.8v LiPo battery, it's 4.4A, hopefully that'll be sufficient -

unfortunately I can't see myself having the pleasant problem of having enough film to run a battery out first.


I've just got to figure out how to solder these beefy battery wires to a new little 4 pin XLR connector and i'll be

able to confirm if it works alright.



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I wired up the battery tonight and it works perfectly. Not sure on total run time once it's fully charged, but

in terms of size i'd definitely recommend LiPo batteries for these older cameras. It's small enough

to velcro onto the side of the motor base.

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From memory, with 16V power supply the constant speed Arri motor draws around 2.5 - 3 amps with a mag. Start up current can spike higher.

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Thank you Dom. I've now got a 12V, 7.2 AH sealed battery, fuse holder with 5A and 10A fuses, and XLR connector etc. Bruce McNaughton advises that this is a good battery for this camera/motor combination, up to 30 fps. The power connection on the motor (Cinema Products) is 7 pin. On the other end of the power cable is a 4 pin Cannon XLR connector. What I need to do now is solder up a short cable with 4 pin female connector at one end, and fuse holder and clips for the battery terminals at the other.


Have I got this right? The positive wire coming off the battery solders to pin 4. Between the positive terminal and pin 4 goes the fuse holder. The negative wire off the battery goes to pin 1. Is it correct that no other wires are needed, so ignore pins 2 and 3? I will wrap electrical tape around all the external solder joins. Later I will get a small plastic case to hold the battery and fuse holder.


Hope I've got this right. Sounds basic but never done it before.

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