I got tired of taking out and putting in 8 AA batteries in my flysky FS-T6 transmitter every time I went out to use it. So I decided to make a single pack that is rechargeable and can be swapped in and out easily. This Mod will only work on transmitters that use (12volts) 8 AA or 8 AAA batteries.
Step 1: Gather Your Parts
3__14500 3.7v Li-ion 1200 mah Batteries
1__JST Power Connector Pair (male and female)
1__3s Balance Connector (male)
Step 2: Prepare the Batteries
Scratch the metal contact points on the batteries so the solder can bond correctly. Take your time, be very careful not to scratch the plastic. This is a very important step because solder does not stick well to shiny surfaces. There are many ways to achieve the same results, I used a dremel on low with a fine point sanding bit. In the past I've used a razor blade to scuff up a shiny smooth surface for soldering.
Step 3: Solder the Pack Together
Its important to double check each connection and give each connection a slight tug to ensure it doesn't come apart. The circuit diagram above shows how a typical 3s battery is wired, use the male JST connector on the pack. Once you are happy with all your solder connections you can wrap the battery in electrical tape. If you want the pack to have a professional look just use 2" heat shrink tubing around the pack instead of electrical tape.
Step 4: Transmitter Mod
Carefully open your transmitter and locate the power wires connected to the battery compartment. Cut the wires so they no longer connect to the battery compartment. Connect the female JST power connector in place of the battery compartment and route the wires into the battery compartment. The pack uses about half the space in the battery compartment and fits perfectly against the back cover once it is closed.