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By Jack Flanders
#186729
Since I had this answered by Sparkfun tech-support, I'll echo it here:
There is no over discharge protection built in to the Thing. Most batteries have a protection circuit built into them though for that. All of the LiPo batteries we carry that have a JST cable on them have over discharge protection built into the battery.
So although the ESP8266 Thing does *not* have protection against discharging an attached LiPo, if your LiPo is one of the ones from Sparkfun with an attached JST cable, the LiPo itself will prevent over-discharge.

Thanks Sparkfun tech-support!

ps: the battery is the best place to put over-discharge protection.