I’ve noticed many people connect their Cores directly to a LiPo. Maybe I’m missing something, but what keeps the LiPo from discharging too deeply thus damaging the battery?
Does the Core automatically shut off when < 3.3 V is supplied by the battery?
I think part of my confusion is that I have a lot of LiPo batteries from my RC hobby and I don’t think any of them have a built-in discharge protection circuit on the battery itself. That circuitry is usually built into the receiver/ESC or otherwise on board the vehicle. Found this article on Adafruit about how these lack any discharge protection.
There are so many RC batteries out there now that I wouldn’t be surprised if there are other people like me that are investigating reusing these to power a Core. It seems that I would need to also use a discharge protection circuit set around 3.2V. Has anyone bought or created such a circuit?
Should I simply give up the idea of using RC LiPos and exclusively use only batteries with low voltage protection built-in? 
What you could do is use a standard LiPo battery protection IC (ebay 
) and use it with a 5V boost converter to supply the core with. You will need the boost converter because the protection ICs have a over discharge at around 2V.
I think something like this is what I need.
Not sure why I’d also need a 5V boost? The above should cut off the battery when it reaches 3.0V, which is really the lowest I’d ever want to drain a LiPo. I’d actually prefer 3.2V but haven’t found a similar circuit with that voltage.
I was looking for LifePo4 that cuts off at 2.0V, I mislooked then haha
but yes, that would indeed work. The 5V boost was needed for the 2.0V cutoff which is too low for the core
Now that I’ve looked into the options, it seems like it would simpler, safer, and not much more money to simply buy different batteries with built-in protection for my IoT projects than to re-use my RC batteries.
Posting this in case future forum dwellers have the same thoughts. 
I also use LiPo batteries for RC applications (helis, planes). I wouldn’t trust mine for any indoor applications as many have had ‘bumpy’ landings
So long as you are happy with the power suddenly going away when the protection circuitry in the battery kicks in.
There are battery monitoring ICs available. I’m also looking at using a simple resistor-divider network and cap to give me an interrupt when the battery voltage falls below a set limit.
Then you can light up a low-battery indicator or land your plane while you still have power.
Yes, that works for RC use but with IoT I may not be there watching the circuit when the battery goes below 3 volts…
You could use the WiFi magic of the spark core to send you a message when the battery falls below a threshold
I used an external resistor network successfully on Arduino, but the design is dependent on the internal 1.1V precision voltage reference present in the AVR processor, and a comparator which allows for comparision of an analog voltage (even outside the range) on a pin with the 1.1v reference. I can find no similar capability in the docs on the Spark ARM chip. Without this capability, if you’re simply reading the resistor voltage on a Spark analog input, the readings you get are referenced to Vcc, so the ADC will still be giving a maximum reading when Vcc falls below 3.6V.
That, at least, was what I encountered on Arduino. If there’s a way to do this on Spark without adding additional circuitry (reference, comparator), I’d be keen to hear since this is an issue that concerns me, too.
Thanks