Battery stops charging at 84% and gets very hot
Solution 1:
Battery heating can be a sign that there's a bad cell in the stack.
The other cells charge up to full capacity and the bad cell then just turns into a resistor, creating a lot of heat as it dissipates the wasted current, and in the case of Li-Poly, eventually smoke.
Solution 2:
Replace your battery. Fiasco Labs is right. Your battery is broken and needs replacing.