Enhancement - Adding a cutout to the PCB for a thicker battery

[peterjc]

Quoting another issue:

How is the battery life on it and would it be possible to fit a bigger battery in that case or is it pretty full?

Left side lasts about one to two weeks, right side two or three months give or take. There is a little more room, the maximum that can fit is 36x16x4mm.

Looking at the case STEP file in FreeCAD (one big model of both sides fully assembled), the bottom case ribs are not in the way of the battery region, so the available height is from z=-4mm (top of the inside floor) to z=+1.6 (inside ceiling of the top case, should be flush with the top of the PCB) making 5.6mm, so a 5mm thick battery should fit snuggly with a cutout. Without the PCB cutout and a 1.6mm PCB, the vertical space from the bottom of the PCB would be only 4mm (as quoted above).

I don't think there is enough slack in the bottom case to shave off any more vertical space, so when @carrefinho wrote this on #17 perhaps he misremembered or would thin the top case here?:

A battery cutout is definitely viable. 601230 (200mAh) should fit, which would roughly double the capacity compared to the original 301230. I stuck with the 301230 in the orginal design primarily due to the size's ubiquity.

Rather than just a rectangle cutout, I would bring in the board edge here, leaving the battery width limited by the case (and the inside of the bottom case is not vertical). The length is bounded to just two choc key widths, perhaps 36mm - as per the current max battery length. You'd have to move the diodes, or remove them - see #16.

That would mean a theorical maximum battery size of 36x16x5.6mm (with same case, new PCB).

So pushing the tollerances with the current case, with a large PCB cutout, you might be able to fit a LiPo 501535 battery at 250mAh (nominally 35x15x5mm). Something like a 501430 180mAh or 501235 180mAh seems a good bet - I didn't find anything at the hypothetical 501435 size. A safe choice would be the LiPo 501230 advertised at 150mAh, better than the current 110mah 301230, but surprisingly not by much for the extra thickness.

(Which if any of these are available with the current design's connector is a separate challenge, see #14.)