Went out to test a NCR18650b (4S4P) battery pack we quickly slapped together in our floppy Skywalker (taken a lot of hard landings). Our hope was to get around 90 mins flight time. The wind was constantly hovering around 20kph, so we never really went for distance.

After some time in the air we got to 60km distance, then 70km, etc. At 90km we decided to fly the battery until the motor cut out, luckily it didn't - went to to 13.2V under load. 

Plane: Skywalker 2014 1800

AUW: around 2kg, not sure

Motor: Sunnysky 600kv X4108S

Prop: APC 12x6

Batteries: 4S4P NCR18650b 13600Mah

Battery weight: 812g

AutoPilot: APM2.6

Total Distance flown: 102km

Weather: Wind 20kph, sunny, 30°C. Altitude: 1634m ASL

Time flown: 129


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  • Hi everyone, since the Tlog is shared, I uploaded it to Exmaps and its available here: http://exmaps.com/e40c4f lowest voltage under load was 12.72V (3.2V per cell), total mAh 11704 and 114.4 mAh/km. Not to sure why a sudden increase in altitude towards the end?  

  • 100KM

    Thanks guys.

    We decided to throw caution to the wind and soldered the batteries ourselves. I wouldn't say it's safe to do so, but it worked for us by using hot soldering iron (150W) and applying no more than 3 seconds of heat at a time.

    A more important thing to consider is that the whole battery casing is negative and there is very little separating the positive side from the casing - on one solder I did create a short by accidentally burning through the very thin insulation - I would recommend using insulated wire (wet noodle) for these connections.

  • MR60

    This is beautiful. How did you practically solder your cells together? Spot soldering? Other method?

  • Moderator

    Nice one let me give you a 100km badge. I might have to get some of those batteries for my Skywalker. Well done.

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