I did not "condition" the battery as discussed elsewhere in the forum, but had been waiting until it got below 40% or so before recharging and the time between charges seemed uniform and predictable. Recently I noticed that it was displaying 100% charge for a long period of time before starting down. I downloaded a free battery app that displayed charge over time and discovered that it stayed at 100% for several hours before showing a linear decay. Then last night, the low battery alarm sounded; the charge was 4% and it head been at 100% just hours before. I plugged in the charger and looked at the battery app after a couple hours; it showed a rapid discharge from 100 to 4 over a very brief period of time (the graph resembled a very narrow "V"). What is causing this? Can I fix it or must the battery be replaced?
The thing with Windows Phone 8 limitation is that apps can only update every. 30 minutes. So for something like a battery app, it can't continuously update every time a charge percentage goes down. However from 100% to 4% seems like you have a battery issue. Go to settings > battery saver. What does the battery info say there?
Also what app did you get? A good paid battery app is Battery Sense and a good free battery app is Battery Status
Try to download one of those and see how things go. A "V" shaped graph would indicate that your phone is rapidly losing battery charge. If your battery life is draining very fast then you have a bad battery and you should get the battery replaced.
When I got my 8x, within 24 hours the phone died out and battery would no charge or respond. I got a new phone and this 2nd one has been good to me so far
I had the EXACT same issue, 100% to 4% and low battery warning. I then charged it up and it has stayed consistent for awhile. Today I saw a fast drop from 89 -50 after downloading some updates. I don't have an answer but you aren't the only one with this issue. My battery generally lasts me 2 days sometimes longer.
The circumstance has repeated several times since my original post. I'd try a new battery but I am not convinced that is the problem. Either the OS is reporting erroneous charge data or something is causing the rapid battery drain. Eventually I'll take the phone back to see if the problem can be fixed, but I guess as long as I repeatedly charge the thing, it may be OK. When the problem happens whem I can't readily charge it, I'll demand a new phone, I guess.
Make sure you turn off Wi-Fi, Tap+Send, Bluetooth and Location when you are not using them. Turn off any background apps that really don't need to be updating all the time. See how that helps your battery life