Gotta love the way they did the first one inside, so they could huff the toxic smoke, and permanently contaminate the workshop with particles of god knows what. Burning pvc makes pcb's, but not sure what plastics are used in the lipo pack.
But they did learn, and took the next one outside.
THE LIPO RULES. NEVER ABOVE 4.3V NEVER BELOW 2.7V DON'T PUNCTURE
Ideal charging /discharging range for Lipo, 3.65v minimum 4.1v maximum
See battery technology section, FAQ thread at the top of the page for lipo noob info.