Is there some documentation on the limits and best practices for using a USB solar panel and a LiPo with an Argon? I’ve got a design in test right now, and what I’m seeing is very little change in voltage between day/night. The XC6802 should be directly charging my device right now based on the datasheet, but the charge LED never is lit, and the reported voltage is pretty fixed at 4.04V +/- .01V over the last 15 hours (yes from indirect sun to over night back to direct sun and voltage is not changing). It’s trickle charging for sure.
- 13W USB solar panel connected to Argon micro USB port
- 2500mah LiPo battery connected to Argon battery JST
- Feather doubler with sensor connectors on the other side
- Sleep while not in use, wake to send data, go back to sleep
- Uses SystemSleepMode::ULTRA_LOW_POWER
- Voltage numbers come from
float voltage = analogRead(BATT) * 0.0011224;
- battery measurement is reported on every wakeup
I can’t test the panel output conditions right now. I have ordered a USB power meter though which will be here tomorrow.
I do have an MCP73831 paired with a photon to compare against. That charge circuit works in the panel setup (same panel, same battery, just a photon using the MCP73831 instead of the Argon). Photon runs, battery shows increasing charge in bright sun. The Argon will run (no battery plugged in) from this panel normally without drops or brownouts in bright sun.
I put the battery out intentionally at 4.1 V to test how long it would take to charge, and it’s fluctuated between 4.1 and 4.03 for the last 24 or so hours (mostly sunny yesterday, bright sun today). I’ve apparently achieved equilibrium at ~4.04 volts. The number hasn’t varied for the last 15 hours by more than +/- .01V. The voltage has never really gone up in any meaningful sense with the Argon.
Where is my design or my assumptions wrong? I can’t find anything to control charging like you can with the Boron, so I have no code to change or manage the PMIC or related.