I don't usually post here, but this time thought I would to help someone save time and money.
Your battery charger might well be below par, but the real problem is your battery - it's buggered, throw it out. A 2.8V readout on a lipo cell at rest is terminal and indicates permanent damage. When the battery is under load, that cell's voltage will drop even further and that's why your ESC is shutting things down.
HobbkyKing batteries are in my experience, average at best and often very poor, especially the bottom-of-the-range blue Zippy packs. Before learning my lesson, I had several brand new packs drop cells (3S pack suddenly becomes 2S, etc.) on the first flight, and some even arrived puffed and gassy before they've even been used. Puffing was a real problem with the yellow Rhino packs and I won't bother with those anymore.
Another thing to consider is that HobbyKing vastly overstate the C ratings on most of their packs, and if you actually try to draw the amps that should be sustainable, well...watch the battery fail before your eyes. A genuine 2200mAh 20C pack should be able to supply and sustain 44A, but those blue packs will never even come close to that before shitting themselves. You'd be lucky to get past 20A.
I've had a lot better luck with the Zippy Compact batteries, so maybe they're a different chemistry, process, something? The 2200mAh 3S 35C packs are a nice light weight and serve about 15A in my Wildcat at full throttle without any drama.
For properly high performance models, I'd recommend Hyperion and ThunderPower, though it would seem silly to put an $80 battery in a $60 foamie.