Bhan you need warranty service, your battery is fused off due to a manufacturing defect or third party charger damage. The most common cause of the latter is the mini 12v to USB adapters. I've seen new-ish laptops so the same thing, sometimes they smoothly drain fast but more often there is a "jump" where more than 60% of estimated power just disappears in an instant. How quickly does it seem to take a charge once it reads as depleted?
Also does any part of the tablet get hot. Because a true discharge rate of that level would indicate VERY HIGH RISK OF EXPLOSION. You need this thing diagnosed and fixed or replaced immediately.