I used to be able to charge both my 3DS and my powergrip accessory at the same time by turning the backup battery on and plugging it in, but now when I try this for some reason it seems to short out and stop charging anything altogether. So far the only workaround I have found is to plug in each device separately. The stangest thing is, when I remove the charger from the wall socket and plug it back in, nothing happens, and it just keeps not charging anything, regardless of if they are plugged in separately, but if I plug in another device into the wall, such as a lamp or my phone charger, it works fine, and after that the 3DS charger works on both the 3DS and the Power Grip, but shorts out again when I try both together. What is going on here? Can anyone explain this to me?

That's weird... now that they're both charged the charger is working just fine... guess I have to make sure they never run on empty...

You're talking about the Nyko Power Grip, that thing that doubles the thickness of your 3DS but adds a ton of battery life externally, right? I've never experienced problems with the actual device charging when plugged into an outlet (except for when I overworked a few outlets when I was in Australia, but that's different), but when I'm playing, and especially when I'm using the R Button, mine occasionally "pops out" slightly, wherein the 3DS and the Grip don't separate completely, but just enough so the Grip stops charging my 3DS. It's very noticeable when playing on maxed out brightness settings. For that, I just press down on my 3DS in the space inbetween the X button and the upper-right hand corner of the touch screen, and it heads back in. Not sure if that pertains/helps you; it's just my observation from using mine for a year.