We have an iPad 2 mini that is several years old with recent issues with the battery. After charging for extended period of time it will display a dead battery symbol and not boot up. After plugging charger in and out for a couple of minutes it would finally start to work and when screen comes up it says it is fully charged. The chargers are same as we are using to charge our iPhones so the chargers are still working fine. When the iPad 2 mini booted it is fully charged and would work fine off charger for hours. Now we can't get it to boot at all and just get the screen that says the battery is dead. It also says its charging when not plugged it but not when it is plugged in. Very confused and need some ideas how to fix this thing.
The battery is failing/dead, the circuitry inside may be damaged, or both. You need to have this iPad serviced and needs to be opened and checked out by an Apple Tech. If it is out of warranty, any reputable 3rd party Apple Tech fixit shop should be able to help.
There's nothing anybody can do remotely - the device has obvious hardware issues. I've handled enough iPad minis in similar shape to be certain of it.
Your best bet is to get a new (or newer) iPad. If funds are tight, Apple has pretty good refurbished models in the Apple Store (US link).