Today I took apart my N9 and replaced the battery with a new one I bought online. Unfortunately the new battery was dead upon connecting it (the tiny notification LED didn't light up when plugging in the battery), but I was able to get it to charge by plugging the phone into a DC outlet. Now when I turn on the phone, the battery always starts at 100%. Phone "drains" to 80%, reboot, shows 100% on reboot. Does anyone know how I can fix this so the correct battery percentage is displayed?

EDIT: Also, when I try to charge the phone I always get an error that something went wrong with the charger.

Use search function. All that its solved here in the forum

I did use the search function. From what I gather, I need to flash my phone. This has just been very frustrating which is why I reached out for help. This forum doesn't seem to be strict at all about duplicate threads or bumping, which is why I thought it would be ok to get a second opinion apart from what I found in my searching. To clarify, I try very hard not to be that guy who posts ten thousand "help i'm an idiot and i don't know how to do anything" threads. I only create a new thread or post when I genuinely am unsure of what my next step should be.