I have an 18000 ma hour version of one these and it will start your car (this one is rated at 450 amps for a short period of time). Not sure what they are doing inside the box to get that current, but they appear to charge “something” up.
They can be used for other things as they have multiple outlets for 5 volts, 13.8 volts, etc. It comes with AWG #4 very short jumper cables.
They deliver extremely high currents for a short period of time, and they do work. I have not actually used it for the radio yet, but others have. We have started cars with them.