Security researcher Charlie Miller has announced that he has found a way to hack the chips that control the batteries in Apple’s MacBook, MacBook Pro, and MacBook Air. Using these chips, he was able to brick (or ruin) batteries, or even install persistent malware that would survive a physical hard drive change.

via Charlie Miller Finds Way to Hack MacBook Battery | News | The Mac Observer.

Basically the heat controllers only have 2 default passwords, which means you can install malware in the bios which overheats and explodes the batteries.