I have a NOCO GB 70 battery charger and a plug-and-jump for my Cherokee. I'd like to use these to learn the avionics in the panel (it's a new plane to me); however, there's nothing in the POH re. how to do this (only a general statement indicating that one can use an external power supply). Plug in the plug-and-jump, attach the battery cables, and then? I'm eager to do this, but also nervous about doing it incorrectly and damaging the avionics. Thanks.