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Voltage and performance


Senior Member
Hi there. I was flying my Calypso this weekend, and ran into an interesting phenomena. The lipo I was using was a new 1300 mah 3s, it came with the plane, and was fully charged when I put it in the plane. I flew for quite a while, and suddenly noticed that when I gave it throttle, the propeller turned, but with no force. It couldn't have been more than two or three revolutions per second. I landed the plane, and plugged in a hobby king voltage checker, and found that I was at 3.5 volts. That's low, but just about everything I read online suggests that 3.3 volts is the magic number for low voltage. What am I missing?


Amateur Extra Class K5TWM
3.5V on a checker is probably somewhere 2. something or less under load. I suspect the battery was flat empty. If you have a computer charger then it will be interesting to see how many of those 1300mAH you put back in to get to full charge. Draining that low is very hard on the battery chemistry (shortens life a lot).



Old age member
There is a lot of difference in quality of the batteries.
Many batteries drop a lot in voltage when you pull some current as tritium says.
When batteries are new and good you will get almost the nominal capacity from them but after some years they are getting "tired" and the voltage will drop under load and you will get half the capacity when flying. The checker will still show a lot of voltage left when the battery has "rested" and might fool you to believe there is "one more fligth".