I haven't tried it myself, but I've seen a couple of posts on the forum that state you can "charge the 12v from the IMA using ACC position," [EDIT] but it's a very slow, trickle charge. [END EDIT] providing that you have all other accessories turned off--no lights, no radio, no fan blower, etc. If so, it may be the case that listening to the radio while key is in ACC position is draining the 12v battery prematurely, if you have some other power draining things running at the same time, and making sure the fan blower and other things are turned off, will provide enough power for radio use only.
Last edited by litz; 04-16-2017 at 12:08 PM.
Reason: added info