What caused Apollo13 to lose their oxygen?

While on Earth, the O2 tank had its wiring damaged during a heating process. The meter registering the temperature inside the tank only went up as high as they wanted the temperature to go, so it had no way of displaying "it's too hot!".

When in use (a motorized stirring process to keep the slushy O2 loose) the wiring caught fire, and the tank detonated. Things burn very quickly and powerfully when given all the pure O2 it needs! I believe the wiring diameter was wrong too, it had not been thickened when they made the voltage 32 volts, from some lower figure. I am not 100% perfectly certain of this but it is how I remember it. If you want to get an idea of what went on inside the tank, see the below YouTube video!