Polarity of power cord, BMPCC?

I'd like to make a custom 12v battery pack but don't know the polarity of the .7mm charge cord, does anyone know if the center is positive or negative?
Has anyone made a custom external battery yet?

I'd like to make a custom 12v battery pack but don't know the polarity of the .7mm charge cord, does anyone know if the center is positive or negative?
Has anyone made a custom external battery yet?

Center is always positive. To confirm just look @ your Switching Power Supply.
And I bought this battery which last 6/8 hours.
One example but you can find smaller batteries
http://www.amazon.com/s/ref=nb_sb_noss? ... ry%2023000

Thank you Surfer, most plugs use center positive but not all....thanks for the info!

But that Amazon sold battery you showed is for car jumper.

Does it work with the camera?