I am using a project which uses an Arduino Uno and a powerboost 1000C. in the manual it says,

LBO - not a leveraged buy out! this is the Low Battery Output. By default it is pulled high to BAT but when the charger detects a low voltage (under 3.2V) the pin will drop down to 0V. You can use this to signal when its time to shut down or alert the user that the battery is low. There is also a red LED connected to this pin.

I understand what is going on but I don't know how to hook it up to the input of an Arduino input in order to do other things when the battery is low.

I had an idea of hooking up an optocoupler (with current limiting resistor of course) but I can't help but feel that is unnecessary. I have some PC817s so if that would work (with 5V and arduino input connected to one side and a 220ohm resistor in series with LBO and Bat on the other end (anode connected to bat)) I'm fine with doing it, but is there a better way?

  • \$\begingroup\$ You should be able to hook it up directly, why do you want something in between? What are you concerned about? \$\endgroup\$
    – Ron Beyer
    Commented May 9, 2020 at 2:17
  • \$\begingroup\$ @RonBeyer Oh you can just hook it up? I am not worried about anything in particular I just haven't seen anything anywhere about this and didn't want to risk ruining my board. \$\endgroup\$ Commented May 9, 2020 at 2:19
  • \$\begingroup\$ @RonBeyer When I hook it up directly, when the powerboats is shut off, the led indicator on board turns on, which would waste the battery life. \$\endgroup\$ Commented May 12, 2020 at 21:22

1 Answer 1


Ok so I went into the Adafruit discord and found the answer. Its a bit hacky but here it is. Solder a wire to the pin that is alone on the onboard transistor. (the only transistor on the board, which is right above the Bat and Vs pins). Then connect the wire through a series resistor (100-10K worked for me) directly to the digital pin.

Then in code if the pin is HIGH, the battery is low.


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