^ There are two options for internal powering of an Aerco: either three nine volt batteries or rechargeable LiPos. The LiPo option has been available for quite some time; my Aerco is a decade old and has them. The only issue with those is that the spacing is pretty tight, so replacing them is not super easy. I seem to recall that someone here (spyder9?) decided to abandon the rechargeables for this reason, although I was able to find some new ones (with a bit of effort). You need to open the case for the 9Vs, but not the LiPos. They are also quite flexible with respect to external powering. Per Jerry (Chamkis), "there is a built-in switching power converter to provide +/- 16 volts for the preamp and 48 volts for the mic, so you can also feed 9–18 volts DC in an external coaxial power jack on the side. The external power jack is floating so you can use a positive or negative or no ground system, so it's very flexible about sharing camera or other available power."
Jerry also says that they are very well shielded with respect to RF. Anecdotally, I have never heard any interference (even when using my phone next to the pre), but that is a sample size of one!