DIY Li-Ion pack for Taranis Qx7

While building my first RC plane, I learned that the takeoff weight of the airplane is very crucial. The rule is, the heavier you are, the shorter you fly. “One does not simply ” dump so many batteries and expect a longer flight time. This fact made me curious about batteries, and that’s where I discovered Li-Ion cells.

I spent some time on YouTube and surprised how people upgrade the batteries of their electronic devices easily with Li-Ion cells that are very easy to come by (they are very cheap or can be recycled from old laptop batteries, old powerbank batteries etc.) Then I decided to build my own pack for my airplane. But before building that, I wanted to practice with small stuff so I decided to make my transmitter rechargable! If you one Taranis Qx7, it needs 6 AA to operate. Luckily, the AA housing is modular and you can replace it with some other compatible battery (they sell official NiMh packs for Qx7). What I needed was 2 Li-Ion cells, JST connectors and some soldering.

I salvaged many Li-Ion 18650 cells from three old laptops and a powerbank which had been waiting to be thrown out. Even though some of the cells were done for good, I still got plenty of healthy ones. After I received my JST connectors and tools, I began soldering. Although it is advised against soldering on the 18650 terminals due to the possibility of degrading the battery by heat, I still went for it since it is a learning experience. Though I used caution not to heat up the battery excessively longer.

After soldering the battery terminals I built a harness that will let me charge the battery with my LiPo charger. Basically, the charger requires a main battery cable and a balancing port. Since the charge and discharge currents are very low, I used the same 22 AWG cable to build everything and simply shorted the main battery connectors to the balance terminals. Finally I finished the pack with a Kapton tape for safety and protection.

I cannot say it is among my best DIY projects, but I am satisfied with the result. In fact it turned out to be good enough and became a permanent replacement for 6x AA batteries on my controller. Looking forward to upgrading more tools with LiIon!