The driver board is 1.25” diameter, there is a Q1 N-FET NCE2060K, and U1 is an 8-pin ic that has been sandblasted to remove the part number, and U2 is a 5-pin with tab ic, D7136. i don’t like that big solder ball, it indicates lack of wetting of the solder to the wire and the device and is likely to fail as a cold-solder joint.
The battery carrier has 3 spring-loaded pins on each end and can be inserted either direction, it is polarity insensitive.
