General • Measuring LiPo battery voltage from VSYS.

Hi Folks!

I'm running a Pico W from a PKCELL LP803860 2000mAh 3.7 V battery connected via a
Pimoroni Lipo Amigo Pro - Lipo Charger.

The charger is VDEV is connected to pico VSYS
The charger (-) is connected to pico GND.

At the moment, I'm sending the voltage readings from the following code:

vsys = machine.ADC(29)
machine.Pin(25, mode=machine.Pin.OUT, pull=machine.Pin.PULL_DOWN).high()
machine.Pin(29, machine.Pin.IN, machine.Pin.PULL_DOWN)
voltage = vsys.read_u16() * conversion_factor

I charged up the battery cell until the charge iight on the Amigo pro switched of, and
this gives a voltage reading of 3.2999996 V

Whereas if I disconnect the battery and power by the pico's USB, i get a reading of 3.9503316 V

I think the battery should be 4.2 when fully charged, which I assumed it was when the orange charger light went out.
I pieced together the code above after looking at various posts relating to similar issues, which mentioned the WLAN
being an issue when measuring VSYS voltage, but I'm using the bluetooth.

Any thoughts on the lower voltage, or perhaps it's fine and I'm getting incorrect readings....

Statistics: Posted by SonSon — Tue Feb 10, 2026 7:12 pm — Replies 2 — Views 40

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