I posted this on reddit first, link here. I've bought a normal working 3DS XL off someone, it works fine, but they guy had around 20+ 3DS and XL units which varied in how they worked. Some were actually retail models that worked fine, but most of them are demo units that only work when plugged in, and also power themselves back on when turned off. I decided to ask if he wanted me to try and restore them, and we struck a deal. I've done hours of reserach into this matter, since I am an amateur tech junkie and wanted to figure out how to "restore" these units to normal working order. From what I've found and tried, upgrading the software and formatting the data on them has no effect, and thus I can relatively safely conclude that it is a hardware limitation on the mainboard. I've disassembled them and cross-referenced the fuses and chips with the normal XL that I have which works as intended, but couldn't find any differences aside from "T" and "E" sometimes marked around the charger port or the battery connector area. I've read that it may be a fuse that needs replacing, or some other engineering hocus-pocus which I am willing to try since almost no one would want a 3DS that only works when plugged in. I am in possession of most toold required for the job, ie small philips screwdrivers, pincers, a soldering iron, etc. I am willing to try quite some things (and I've already tried some already) since he won't really be bothered by losing a couple units on testing. What is peculiar is that some units will function like a demo unit when plugged in, but when I replaced the battery, it did function like a retail one. At the current moment, I have a regular 3DS that functions like a demo unit, a 3DS XL that also functions like that, and a 3DS XL that doesn't charge at all, BUT works perfectly from the battery. This last one I have tried to fix with some soldering and rechecking all the contacts, but to no avail. The 3 aforementioned units have been stripped of parental controls and upgraded to the latest 9.8.0-25 firmware. I can list all the forums I've been to, but I've been to alot (even page 2 of Google search results...) and tried many search options. Most of them were just "dead battery" threads but some were helpful and tried to speculate what the possible solution could be. Thanks in advance if anyone of you knows what to do, because I am not giving up on this unless someone clearly states (with proof, preferably) that it is impossible to modify demo units to a normal working state.