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Can I use Qt Py with a LiPo battery?
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Can I use Qt Py with a LiPo battery?

by neilly98 on Sat Apr 24, 2021 12:43 pm

I'd like to use a 3.7V LiPo battery to power my microcontroller (a Qt Py breakout board), but it would require a voltage regulator since LiPo voltages can vary depending on charge and the microcontroller on board (a SAMD21E) requires 3.3V.

When looking at the schematic of the Qt Py, I noticed that it actually already contains an AP2112K voltage regulator chip so that a 5V USB-C input can be used. So I'm wondering if it's possible to just connect my LiPo to the 5V jumper? My battery voltage can vary between 2.8-4.2V, and the AP2112K can handle 2.5-6V.

https://imgur.com/awnjoft This shows the three sections of the Qt Py schematic relevant to the voltage regulator. From looking at this it seems that just applying V+ from my battery to the 5V jumper (potentially through a diode) would work just fine? The diode thats already there would prevent damage to the USB port, and the 5V jumper is only connected to the regulator, so a varying voltage from the LiPo shouldn't affect anything else right?

neilly98
 
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Re: Can I use Qt Py with a LiPo battery?

by dastels on Sat Apr 24, 2021 3:06 pm

I would connect a battery through a diode to the 5v pin/pad. That would protect the battery when USB is also connected. they would both be isolated from each other and the higher voltage of the two will power the board. Note that you'll need to remove the battery to recharge it.

Dave

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Please be positive and constructive with your questions and comments.