WARNING Battery Danger

[guitardoc64]

Originally Posted by nxtech3

id like to see pictures, it probably leaked battery acid, which would cause the "burn" and the smell of a chemical reaction. All comes down no matter what to a defective battery. If it was OEM i would be raising he** with HTC.

For the record, in the interest of public knowledge;
Lithium ion batteries do not use acid. My guess is the battery case was either bent by your a$s sitting on it and cracked. The electrolyte leaked out into the cotton and reacted with moisture in the fabric in what is known as an exothermic reaction.
From wikipedia:

Liquid electrolytes in Li-ion batteries consist of lithium salts, such as LiPF6, LiBF4, or LiClO4, in an organic solvent, such as ether. A liquid electrolyte conducts Li ions, acting as a carrier between the cathode and the anode when a battery passes an electric current through an external circuit. Typical conductivities of liquid electrolyte at room temperature (20 oC) are in the range of 10 mS/cm, increasing by approximately 30-40% at 40 oC and decreasing by a slightly smaller amount at 0 oC.[20]
Unfortunately, organic solvents are easily decomposed on anodes during charging. However, when appropriate organic solvents are used as the electrolyte, the solvent is decomposed and forms a solid layer called the solid electrolyte interphase (SEI)[21] at first charge that is electrically insulating yet sufficiently conductive to lithium ions. The interphase prevents decomposition of the electrolyte after the second charge. For example, ethylene carbonate is decomposed at a relatively high voltage, 0.7 V vs. Li, and forms a dense and stable interface.