THIS JUST IN...
One of our Tech's just got off the phone with a customer who this last weekend was running at the TCS race up in Washington and they had an IB NiMH pack blow up on them. The pack was sitting on there pit table for about 5 minutes after it had been charged and was completely disconnected from anything when it went, luckily nobody was hurt but his pit towel did catch fire but was quickly extinguished.
Looks like no battery is safe.