FiiO BTR3K Shell for a bigger battery

The body fits a 55x45x4 mm battery. I used a 1200 mAh battery. For reference, that lasts around 26 hours of use with LDAC codec.

Also included is a special version of this model and a mount for it to fit onto Sennheiser HD650 headphones headband. It has extra extrusions that slot into the mount.

If you are gonna do this mod: Make sure to cut the original cables high and solder the new cables onto them. Do not try to desolder the original cables at the PCB contact points, you will likely ruin your btr3k. And be careful when disassembling the thing, the glass panel might shatter (ask me how I know). Better start with the back panel.

NOTICE: The topology is pretty bad, since I barely have any experience modeling. And the model is designed to be printed on my poorly-runed Ender 3 V3 SE, so you should expect to need to tune it for your own printer. The tolerances might not work well for you. The screw holes are not threaded, my printer simply wouldnt be able to print such fine detail. The holes came out too small, so I had to enlarge the them with a sewing needle.