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Using a LiPoly Backpack to power Arduino
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Using a LiPoly Backpack to power Arduino

by no_u on Thu Sep 16, 2021 4:43 am

Hi!

I want to run an Arduino inside a device, using a LiPo battery. Since it's embedded I also want people to be able to charge that battery via USB when it's not in use. The LiPoly Backpack for the Trinket seems perfect, but I'm wondering if I can use it with an Arduino.

From what I gather the Backpack has a BAT pin and a 5V pin, and if the BAT pin is higher (ie if there's no USB connected) then it discharges the battery. Therefore I imagine that if it's attached to the USB breakout and it's plugged in/not plugged in the same logic applies, but I'm not sure if I'm missing something here, or misunderstanding how it works.

Would the setup below work for using this with an Arduino Uno? (I'm using a USB breakout because it would have to be accessible from outside the enclosure.)

I would just buy a Backpack and try it out, but since I live outside of the US/Europe shipping is really expensive so I'd rather make sure it's actually what I need.

Thank you so much for your help!
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no_u
 
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Re: Using a LiPoly Backpack to power Arduino

by adafruit_support_bill on Thu Sep 16, 2021 6:03 am

That will not work as drawn. The 5v pin on the backpack is an input to the charge controller. It is designed to be connected the USB pin on the Trinket. It will not work if you short it to the BAT output pin. You should connect the 5v pin of your USB jack breakout directly to the 5v pin of the backpack.

Note that your Arduino will only see battery voltage on the VIN pin. That is under-spec for most Arduino boards. Some may work anyway, but it is not guaranteed. A PowerBoost shield might be a better choice: https://www.adafruit.com/product/2078

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Re: Using a LiPoly Backpack to power Arduino

by no_u on Tue Sep 21, 2021 4:42 am

Hi, thanks so much for your reply! I appreciate it. I hope you can clarify one thing: With this setup, can I not power the Arduino from the USB when it's plugged in?

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Re: Using a LiPoly Backpack to power Arduino

by adafruit_support_bill on Tue Sep 21, 2021 5:27 am

Both charger output and battery are wired in parallel with the Arduino, so yes your Arduino will receive power when the backpack is connected via USB.

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Please be positive and constructive with your questions and comments.