Wiring for Solar and Battery

[Matt Auer]

Hi All

I have the following components for my project:

• WiPy 3.0
• Expansion Board 3.1
• USB / DC / Solar Lithium Ion/Polymer charger (https://core-electronics.com.au/usb-dc-solar-lithium-ion-polymer-charger-v2.html)
• Polymer Lithium Ion Battery (LiPo) 3.7V 2400mAh (https://core-electronics.com.au/polymer-lithium-ion-battery-2400mah.html)
• 6V 2W Solar panel (https://core-electronics.com.au/medium-6v-2w-solar-panel-2-0-watt.html)

I just wanted to check my wiring before I actually do it because this is my first pycom project.

Solar Panel -> DC Port on Charger
LiPO Battery -> BATT port on charger
LOAD Port on Charger -> JST on the pycom expansion board

Is this correct or is there anything else I need to do?

Cheers,
Matt

[Matt Auer]

Thanks everyone for the advice.

So sounds like I need something like this to drop the voltage from 6V to 5v https://core-electronics.com.au/lm2931-ldo-5v-voltage-regulator.html

[Antonis Gotsis]

@jcaron You are absolutely right, good point. I was indeed referring to a "production" use-case where one wants to use solar panel for unattended operation.

[jcaron]

@Antonis-Gotsis beyond conversion of voltage levels and battery charging circuitry, the expansion board also provides the USB-to-serial conversion. In production this may not be needed but during development this makes quite a difference. Of course one could use a separate USB-to-serial converter.

[Antonis Gotsis]

@Matt-Auer Actually the expansion board is useless in such a setup, as you can drive the LOAD port of the charger directly to the VIN pin of Pycom. But then you may need a regulator between them (check https://learn.adafruit.com/usb-dc-and-solar-lipoly-charger/using-the-charger?view=all#downloads) in order to be sure that you don't violate the 5.5V limit for supplying pycom.

[jcaron]

@Matt-Auer one issue I see in this setup is that if you connect the USB port on the Expansion Board, it will try to charge the battery, which is actually the charging circuit. Not sure if that is a problem or not or if that can be disabled on the expansion board.