LiPo battery powering Moteino, options...

[Felix]

I can say that feels very true although I cannot confirm the exact numbers themselves, but certainly the LiPo will last a very long time at the 10-20% top voltage then start to drop faster and faster.

Felix, I'm not sure what end points you're referencing, however, a LiPo discharged (and not recharged) in a lowpower environment like Moteino will spend the bulk of its time between 4.0-3.7 volts.  Once you get to 3.65, game's over, you're 'about to'¹ fall off the cliff.

It's just from my general use of LiPos in my own nodes. I think we're in agreement, maybe the way I said it wasn't very clear

[WhiteHare]

Thanks, Tom, for the references.  They made for good reading:  in addition to the cut-off voltage, the other two significant factors would seem to be depth of discharge and temperature (Tables 2 and 3).  The table you highlighted appears to assume a Depth of Discharge of 100%.  It looks as though limiting DoD to 10% would give another big boost of longevity.  So, I can believe JamesBryant now that by conservatively managing the three factors (cut-off voltage, Depth of Dischard, and temperature) could give >10x improvement in the useful life of a LiPo.  Impressive!

Provided you have the space, using LiFeO4 as the rechargeable battery chemistry would appear to help with the heat issue.  As near as I can tell, LiFePO4 seems to actually perform *better* at higher temperatures, whereas regular LiPo's perform worse.   Also, LiFeO4 would give a fairly flat voltage curve between 3.2 and 3.0 volts, which would also seem to be a good match for the Moteino and these HopeRF radios (which can tolerate at most 3.6v max), as you wouldn't need a voltage regulator.

[WhiteHare]

If the magic number is 3.92v for regular LiPo batteries, what should it be for a LiFePO4 battery?  This series of charts suggests it maybe (?) is between 3.3v and 3.4v:  https://www.powerstream.com/lithium-phosphate-charge-voltage.htm

Interestingly. his measurements showed that one of the allegedly LiFePO4 batteries was spiked with Cobalt.  I do wonder whether that spiking carries with it possible negative safety implications, as for me the better safety profile would be one of the reasons for picking LiFePO4 in the first place.