Over-Discharge of 3S LiPo

[axelnied]

Hi,

On a previous flight I might have over-discharged a 3S LiPo with 5000mAh (NanoTech) 25C-50C, below 10V, or 3.3V per cell... This morning I did another flight and wasn't sure if the performance of the LiPo was as good as on previous flight, before over-discharging.

For the last flight I plotted Vin (from the flight-log).
My Question: There is a HUGE drop in Voltage at the beginning of the flight! Is this considered normal? Or is this a result of the over-discharge?

Remark: I am in the process of installing the TM1000 telemetry unit for the Spektrum to ensure not to drop below 11V ANYMORE!

[bluuu]

It's normal in LiPo baterry. It's performance characteristics. Look at this chart:

[Max]

Hi Axel,

That discharge looks fine. Although you'd need to compare it to the same battery before the incident, or a similar battery, to see if there is really any significant difference.

I think 3v is technically the limit a LiPo cell is OK with, and from what I've read it also makes a big difference how long the cell is under-voltage. A few minutes or even hours isn't necessarily going to hurt anything. Of course "babied" cells probably last longer.

I have a friend who bought 2 4S Nano packs and left them at storage voltage for a couple months, only to find out later that they all self-discharged to ~1v per cell.

-Max

[sandmen]

About the Vin, I will try a version with a VinLpf.
On your chart, you can see, we can get a little bit disturbance into our throttle signal.

[axelnied]

To All,
Thanks for your responses... I have an identical LiPo pack en-route, and I will test it against that one to see if there is a difference (permanent degradation of the existing pack).

Sandmen,
VinLpf? What it is and how can I chart it?
I flew this morning for exactly 10 minutes and collected approx. 120,000 samples... Is that the LOG-sampling-rate? 10,000/min (=200 Hz)?