They Lost AC power 4 minutes before the crash. That'll happen when you lose both engines.

This airframe was built in 2009, and independent battery for the black boxes was made mandatory for aircraft built after 2010 I believe.

Hope they change this and retrofit.

I don't know, I doubt these recorders are made by the aircraft companies.

Aren't they mostly self-contained units, and just connected to aircraft power to maintain their batteries?

I'm a lot more suspicious.