I use old tired LiPo's to power :

Tx's (the power drain is so low even a really bad LiPo works fine !

Soloshot remote camera via BEC and charge socket 

Mini Digital cameras via BEC and charge socket

Bench testing gear

Ignition and RX gear in fuel planes via BEC

For a long time - I just trusted them and didn't think about how low I dragged them .. they didn't seem to care ... but now I use LVC LiPo checkers ... small plug into the balance lead jobs ... so I now get an alarm when any cell gets low.
I am even using the Quanum Battery Alarm when I am remote from the item powered such as the Soloshot camera ... 
I'll fly anything if I can launch it ! Youtube : solentlifeuk
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