Adding solar charging for Bangle watch

Hi,

I want to see if I can convert the watch to "solar" power,
by adding Vishay Photodiode "BPW34" (https://www.vishay.com/docs/81521/bpw34.pdf)
in the corners (left/right to GPS module, and same on bottom)

According to website, the power consumption:
( https://www.espruino.com/Bangle.js#power-consumption)
is "100% CPU usage running JavaScript - 7mA",
and from what I found, this about the same as one Photodiode produces in full sun light,
so theoretically, it looks possible.

Does anybody know if this is possible regarding the circuit, or any limitations ?

Also space-wise, I was searching to see if the files of the case and inner frame models, are available anywhere for 3D printing, but couldn't find it, are they available ?

Thanks for your help,
Si.

That'd be interesting - although I'm not sure if those cells produce that much power. https://www.sparkfun.com/products/9541 seems to imply it's less than 0.05mA per cell at 0.3v.

I think ideally the easiest thing would be if you could get enough of them in there that in series you could make the voltage up to ~4v, then you could connect it straight to the battery. Input power is small enough that overcharging is unlikely to be a problem.

I'm afraid that right now there are no 3d models of the case or inner frame available. Someone was going to look into it for the case but that never happened - however actually making your own model for the frame should be pretty easy.

I'd say there is not enough solar energy in such small area to charge device like bangle. Even pocket calculator that can live years on single button cell battery would probably not run from that photodiode.

I tried to use small solar panel with DS-D6 fitness tracker running Espruino, the panel was called "Solar Panel Mini 0.15W 5V 53*30mm" ($0.75 a piece on aliexpress) and during one very sunny summer day it almost managed to charge the tracker from empty to full. So since it lasts few weeks on one charge this panel would perhaps work as sustainable source even during cloudy days for some outoor BLE sensor.

Thanks for your answers.
I confess I cant read all these specs sheets.
my value of 7 micro amp, 450 milli volts, per cell in full light, is from this video:
https://www.youtube.com/watch?v=rSRclKWZFWY

That's sounds about right - but a microamp is 1000x less than a milliamp :)

My excuse is that I use the watch as a calculator,
and the battery ran out (-;