Customer:
I want the Inkplate 10 to work with a li-ion battery and solar panel that charges the battery and powers the device. I purchased a solar panel with maximum output power of 5W and output voltage of 5V. When I plugged the solar panel into the Inkplate, the battery started charging but the Inkplate didn’t respond until I unplugged the solar panel. I tried plugging the solar panel in without the battery and got the blue light, but the Inkplate still didn’t work. Why is this happening and what can I do so that the Inkplate charges the battery and operates with a solar panel?
Originally submitted via email support on 26 July 2023. Migrated to the forum for community visibility.
Soldered Support:
Where do you connect the solar panel to the Inkplate? I suspect the panel can’t provide enough current to the Inkplate when it starts, which would prevent it from working. Please provide more information about your connection method.
Customer:
I connect the panel via the USB Type-C connector that came with my solar panel. I’m trying to achieve charging the battery from the sun so the battery can power the display. When I put the panel in the sun it charges the battery, but the panel won’t power the display. If I remove the panel from the sun, the screen starts working. Is there code I can write so the screen works only from the battery while still being charged by the solar panel? Or do I need a more powerful solar panel to both power the screen and charge the battery?
Attachment omitted in migration: 10.jpg
Soldered Support:
Inkplate has an auto-source power detection circuit that detects USB power and switches from battery to USB power. If there’s no USB power, it switches back to the battery if one is connected.
When you connect the solar panel to the USB port, Inkplate attempts to power from it, but the supply isn’t sufficient and the display won’t refresh. The auto-source detection circuit disables the battery, so you can’t power from battery and USB simultaneously.
One solution is to solder the solar panel directly to the charger for the battery and power the Inkplate only from the battery. You need to cut a trace on the board and solder wires from the solar panel to the charger. Then the solar panel will charge the battery and the Inkplate will always be powered by the battery.
Customer:
When I plug USB from a PC it works and charges the battery at the same time. Can you check if it’s possible to disable the auto-detector via code so the Inkplate always works from the battery and charges from USB? Can you also check the minimum wattage or amperage the Inkplate needs when USB is plugged in to work?
Soldered Support:
You can’t disable the automatic source detector from code. What you can do is remove that circuit and use the Inkplate as you described: charge from the solar panel and power from the battery.
To remove the auto source-detector circuit, you need to remove one MOSFET and one diode, then connect the two pads together. Be careful when removing components as excessive heat can damage the e-paper panel. I suggest applying plenty of solder to all three pads of the components before removing them.
We measured the current for Inkplate at around 300mA. When using WiFi the current is higher. There is a 500mA fuse on the board, as USB specifications require a 500mA limit.