09 September, 2006

Battery Performance

Say something for buying good LiPos. I just finished running my thermal survey. I set the plane up just as it will be flown, and measured temperature at the battery and temperature at the rear end of the cooling tube. After a run (with an 8x4 prop) of 5 seconds at max power and 120 seconds at three-quarter power, no change in temperature was measured at either location.

This was followed by a 2 minute cooling period, and another run of 5 seconds at max power and 120 seconds at 5/6 power a 2F change was measured at the battery.

I then removed the thermocouples and ran alternate 2:05 run/rest cycles (using 120 seconds at 5/6 power). I stopped after completing 6 more cycles (for a total of 8). All this was done with a single Thunder Power 3S 1320 mAh pack.

With the correct propellor, a 2 minute climb should net somewhere between 500 and 1000 feet. This should translate into 3-5 minutes of gliding with no lift. With two packs, it should be possible to fly for 70 minutes on a single 3S-2P charge.

I had better bring a chair.

An update. I charged the single LiPo cell that I used for the battery tests, and apparently, only 62% of the capacity was used for those eight runs. When I redid the calculations for this new battery figure, it seems possible to get a flight time of nearly 3 hours!

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In fact, I just got off the treadmill...