Originally Posted by MikeAnderson
Pack 1: TP 3800 ProPower 45C 6S purchased from DraganFly: Worst cell IR=4.92. Calculated C-rating =18
Pack 2: Turnigy "Blue" 3600 30C 6S purchased from HobbyKing: Worst cell IR=4.16. Calculated C-rating=20.
In fact one of the two 6S Turnigy packs had a dead cell on arrival, so I paid a LOT for the one surviving pack. But to see that the TP pack is no better is discouraging.
These are used in an EDF that pulls no more than 80A but flies most of the flight at part throttle - say 50 A. So they are both seeing less than the calculated max amps and both should last as long.
I don't seem to have good luck with selecting "good" LiPos.
Those figures do look higher than I would have expected, but not dramatically so.
Are you measuring at 22degC and leaving the packs in that ambient temperature to settle for at least an hour ( preferably more) ?
Also how old are these packs?
It just demonstrates the lottery there is in buying lipos. I have had some Turnigy Blue which are really good; a 2200 25C pack with Cell IRs of mid 4s and some 5000 25C packs all showing cell IRs of just over 2milliohms suggesting that the C rating is near enough genuine. I have done several full rating 25C test discharges on the smaller pack and flown it a fair amount and it is still fine after about 3 years. On the other hand I have had some poor Turnigy blues and even worse Nanotechs; either they change suppliers or have poor quality control.
I don't think you are alone in your findings.