It's a known issue with their bullet connectors. Get some ProTek solid 4mm bullets to plug into the battery and you should be fine. The problem (from what I was told) is their connector vibrates around and causes arcing inside...which melts things. I had this happen to one of my nano-tech 6000s as well. It melted the crap out of one of the terminals, lucky once I swapped to the 4mm solid connectors from ProTek....the problem went away (so far) and the battery is actually still useable.

These are what I used: http://www.amainhobbies.com/product_...nectors-4-Male

They are on backorder, but they have a male/female set that is usually in stock. Other brands will probably work as well...just not the springy crap connectors that HobbyKing ships the batteries with...

Hope that helps!