@bartp The model name of the liPo batteries is they dimensions, for example: DTP603443 - "60" is 6,0 mm of max tickness, "34" is the max width of 34 mm and "43" is the max lenght of 43 mm. So with the dimensions you can find the capacity you need.

Use pytrack.py from https://github.com/pycom/pycom-libraries/tree/master/pytrack/lib. Copy pytrack.py to /flash/lib. Test: import pytrack py = pytrack.Pytrack() print( '{}V'.format(py.read_battery_voltage())) Dispaly is 4.686702V hope it's help you.

@scg94 Even if a solar cell is mostly a current source, I would limit the voltage to about 5V, to be compliant with the regulators and the interface you are using. About the charge current look at the documentation here : https://docs.pycom.io/pycom_esp32/_downloads/exp_v03_pinout_v13.pdf It's 450 mA (with jumper) or 100 mA (without jumper).

@robert-hh Oke, will make a test program. When USB is connected it indeed has a higher voltage :'). That was another mistake/issue I had :). Thanks a lot, again!

Hi @smssms You could try a 2000 mAh LiPo Battery - https://shop.pimoroni.com/products/lipo-battery-pack I'm sure you can find these cheaper/closer to where you are located but I know these work well as I've used them before from this specific supplier.

@bucknall Thanks. Purpose would be to (re)charge the 6600mAH batteries offsite, and replace an empty battery when needed. Any idea how long approximately (is it days, months) a 450mA/6600mA battery will last when only sending every 1 hour a LoRa message?

Yes I have done this with this board and others that need a 5V input. It was as simple as putting in a zener diode in between the panel and board as a cheap, simple voltage limiter cheers Paul