BP series
The battery was connected oppositely, leading to blowout of fuse and damage of AC output part MOS tube.
1,According to the customer's response, after replacing the lithium battery, the front MOSFET bursts. It can be judged that the voltage of the replaced lithium battery is too high that exceed the voltage range the machine can withstand, causing the front-stage MOS tube to burst.
2,Change fuse and MOStube.