Whether you are installing a hardmod, or replacing a bad part.The struggle is real when it comes to wanting to test whether or not what you've done works. I suggest just putting the back cover back on before attaching the battery, but if you intend on attaching the battery with the back plate off, make sure it is faced the right way. Placing it the wrong way reverses power, and blows fuses in both the power board and motherboard. Such a simple mistake can cause a huge headache for those who are not experienced with electronic repair. With that said, you should seek experienced help to service your system anyway, but some can't afford parts and labor, and will attempt it themselves.