I love flying and DIY.
I checked that some people fly a lot of time with wings with these batteries, so I decided to do my own 18650 battery.
Step 1: What Do You Need?
Step 2: Prepare Your Batteries to Solder
With one knife scrape both poles, plus and minus.
Join the 4 batteries with a measuring angle square and put some hot glue.
Step 4: Soldering
Put your solder iron at 350/400º degree.
Put iron solder for 2 seconds on the battery pole and put enough solder to wiring.
Step 5: Wiring
Step 6: Heat Shrink Cover
Cut a little piece of heat shrink tube more 20mm than length of 18650 battery.
Step 7: Already Done to Fly.
A comparison with Tattu R-line 1550mAh battery.
I can fly with my Reptile S800 Sky Shadow 40 minutes, important to say at 25% throttle.