2000mAh battery upgrade for the Sonicake Pocket Master: since the battery port uses a standard JST connector, this is pretty much a drop-in upgrade aside from the fact that I did have to design and 3d print this riser to give about 2mm extra height to accommodate the thicker battery. The battery gives the Pocket Master about double the life.

So far, it works great and the capacity rating seems about right. I've been running it with bluetooth on for 90 minutes without any bars going down on the battery capacity meter, so expect this will approximately 5.5-6 hours. 

I had to use longer screws to reach the holes. #4 x 1/2" wood screws to be exact. The stock JST connector is secured with hot glue which you need to peel off first. Remove the old battery carefully, it is stuck on with an adhesive pad and excessive bending or compressing the battery can cause it to catch on fire. Untested Tip for removing the old battery the board without bending it: use unwaxed dental floss to cut through the adhesives. 

Note that I eventually secured the battery to the bottom plate (not the PCB) reusing the sticky pads from the stock battery. That gives enough space for the chips on the board to have some ventilation. 

The specific battery I purchased for the upgrade https://amzn.to/4pG88FV (affiliate link). There are cheaper ones available if you look around, but quality and may vary greatly and I have heard many cheap ones falsely advertise their capacity. This one was decently reviewed. Make sure the red and black wires match the original battery polarity order (red on top, black on bottom when looking at the back of the pocket master).

Update: I have added a 4mm riser option if you want to experiment with larger batteries. The original model (2mm) is sufficient for 2000mah but I have not tried with other sizes.

Update 2: Looks like some versions of the pocket master have some extra capacitors on right side, preventing proper fit.Try the 8 or 10mm models if that is the case. You will need longer screws.  If the board looks like the one in my pictures, the default 2mm should work.