LiPos for Syma left for months, still good!

[DanMan32]

As u mentioned in a topic a few weeks ago, I plan to teach a class on drones. Really it will probably be a workshop sharing ideas and experiences.
So I thought I'd check out my old Syma and see how the batteries withstood being left to themselves for months, probably more than a year.
They still had a charge, strong enough to fly, even after months! One is swollen but even it could fly the little guy.
Now I haven't tested how much capacity they still have. New, they last about 7 minutes or so.

If cheap batteries with no intelligent management, typically drained to power down, about 3.0v, imagine what our DJI batteries can withstand.

I believe heat is the biggest killer of LiPos. Leave them in the trunk of your black car outside in a southern state, they're bound to suffer a premature death even if you adhere to going no lower than 30%, storing at 60%, and never leaving them at either extreme for more than a day.

Granted, the load in flight will itself cause the battery to heat, especially as it ages and encounters increased internal resistance.

 

[DanMan32]

I dated the batteries with a marker, they were dated 11/2016. More than two years!

I just put them on a charger, they finished quickly. Either that's good in that they really did hold their charge and most of their capacity, or they aren't accepting much of a charge.

The charger is a cheap 5 battery USB charger, but I checked out the ICs it uses (one per battery) and the specs properly adhere to LiPo standards: constant current until top voltage is reached, then constant voltage until current drops to a certain threshold.