The SkyBean SkyDrop is a great small and light paragliding vario that contains even some advance functions like airspaces warnings and task navigation. I've bought a second hand vario few years ago. It worked pretty well and I really enjoyed its features and the open source philosophy of the design (sources on GitHub). However as it aged, the battery life dropped significantly leaving me with only about 1 hour of reliable flying. Opening the case revealed an inflated LiIon battery. The manufacturer sells a double battery kit (LiIon plus bigger vario back side cover), the price is not horrible, but I could get the LiIon battery with similar capacity and added protection circuit for about the cost of shipping, so why wouldn't I experiment a bit?
Battery upgrade
The original battery is fixed inside by piece of sticky tape on GPS module and SD card slot. Do not pull it by force, twist it instead or you damage the SD card slot - ask my why I know that... The slot separated from the PCB quite cleanly, only few pieces remained soldered, rest just fell away. After going through like 4 different slots I had in my junkbox that didn't fit I had to ask the manufacturer for the exact type - it's the DM3D-SF, if you ever needed...
The stock battery was something around 1000 mAh, I've ordered an 1800 mAh and started working on the back cover. The back case shape is not an easy one, it's quite curved - I put it on a graph paper, drawn a line around and started measuring the width every 5 mm of height, after a bit of magic in a 3D CAD I've printed the first prototype.
Few iterations later I ended up with something that fits the vario perfectly and increases the battery area enough to fit the new battery together with some sticky tape to keep it in place - I've glued the battery to the case instead of the SD card slot.
Don't forget to calibrate the new battery afterwards - charge the vario fully, start calibration (Settings -> Advanced -> Calibration -> Calibrate battery), unplug the charger and wait for a full discharge.
When looking for airspace files compatible with the skydrop, I found the original design files for the Skydrop back cover, so I could save some time drawing and debugging them...
Display cover
As I usually leave the vario somewhere inside the bag together with the harness and wing, it happens really often that the button gets pressed while the bag is in a car trunk, turns itself off and starts beeping. And if the radio is noisy and the bag is buried deep below other bags, I don't hear it and first thing I notice at pre-flight checklist on top of the hill is an empty vario battery - not a good way to start an XC flight.
Having the back cover outline already measured, I simply added few millimeters on each side and after two more iterations a perfectly fitting cover was born. It's a snug fit, it holds perfectly while it's still easy to remove. And no more accidental turning on, no more discharged batteries...
Files
- OnShape design of extended back cover
- OnShape design of display cover
- display_cover.stl
- back_cover_extended.stl
