I just successfully repaired a Botvac D85 that had a similar issue. I connected my computer to the USB port and saw an error flash that said the battery was overheated. This caused the main board to automatically power off. The root cause for mine was the Fuel Gauge IC. It took a hot air station and some patience. You might give this article a look. http://www.robotreviews.com/chat/viewtopic.php?f=20&t=20413