dark current noise

and can use an ac adapter as an alternate power source

That's nice, I was not aware of that possibility. But you could still make your own solution for that problem, as described here by another forum member.

Excellent, so there's a solution to making an alternate power source for the E-PL series of cameras?

I'm guessing a similar thing can be done for any camera, really. But I'm not really good at stuff like this, can't even say how hard/easy that would be.

In that thread he mentioned USB "power packs" I'm really curious about what that might be.

No idea.

If you read through the thread linked above, you'll see that in it, I posted a link to *another* thread, which is where the USB power bank was discussed in more detail. That other thread is:

http://www.dpreview.com/forums/thread/3938674

That person is using a fairly-special USB power bank with an adjustable voltage output. He set it to 8.4V output (within the range of output for Olympus batteries, and likely also Panasonic), and made a setup to allow feeding that to his camera.

If you want more info on options for longer runtimes, at least for Olympus cameras, read through those two threads. I made a simpler setup that what faithblinded did, but in his thread (http://www.dpreview.com/forums/thread/3939601#forum-post-56938637 ) I posted info on my setup.

It gave me 8 hours of time-lapse when I tested it, on my E-M5ii, up from about 2.5 hours on the Olympus battery. If I needed it to run longer, I could make a larger battery pack, or add a second pack in parallel with the one I already built.