The tutorial for the PowerBoost 1000C
(great product by the way) could use an enhancement. (It would have saved me time and a PCB mod.)
The tutorial currently describes the LBO pin as follows: "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."
This description makes it seem as if you should connect the LBO pin to a micro-controller input, which I believe is technically correct. However, if you use a SPST switch to connect EN to GND when you want your project to be OFF, then the Low Battery LED is energized (until you turn your project back ON). So while the significant power draw would be stopped, the ability of the project to programatically warn the user to charge the battery has the trade-off of slow battery drain while OFF. Not optimal. [Yes, I could probably de-solder a component on the PowerBoost to stop this power drain; however, my SMD de-solder skills are really bad and I'm working on a through-hole project so that beginners can build one themselves.]
forum post describes a suggested use of the LBO output. It claims that by using an ON-ON SPDT switch and connecting EN to common, GND to one side ("NC" side of the switch), and LBO to the other ("NO" side of the switch), then the project can be turned OFF, and can turn itself OFF when the battery is low. For what I am working on, the user doesn't really need an advanced warning.
I'd recommend that the PowerBoost 1000C tutorial be modified to suggest this as one use of the LBO pin.