How to replace it
1．Take the plastic cover off the battery bottom.
3．Take the original pack out of the house.
2．Press the red clip at first and then separate the housing.
4．Desolder the red wire and blue wire off the pack and then re-solder them back to new pack. Step by step to put the new pack back to house. Done!!
1．Unscrew the 4 screws to separate the battery house. One of them has a seal to prevent unauthorized opening, you may use a wood screw to drill into the seal to pull it out or, just drill some holes on the house to take the seal out.