If you’re interested in upgrading your FrSky Horus X10(s) Express with a 2S 5000 mAh 21700 battery pack and in increasing your radio’s autonomy, read on.
I cycled (full charge, full discharge, and full charge again) both, the old and new battery packs after completing the installation. The results indicate an increase in the available capacity of about 60% and probably a few additional hours of air time per charge. Compared to the previously used 2s 18650 with a nominal capacity of 3400mAh, the new 2s 21700 pack with a nominal capacity of 5000mAh has an available capacity of 4165mAh. While the figures are likely to vary from pack to pack and are influenced by many factors, such as your charge’s cycling settings, they nonetheless indicate a notable increase in autonomy.
The radio takes care of charging and balancing the battery, just as it does with the standard18650 battery. The charging simply takes longer due to the larger capacity of the 21700 cells.
To upgrade, you will need:
Firstly, remove the four screws on the back panel of the radio and lift the back panel off. Remove the six screws on the standard battery tray, then remove the USB plug board and then the battery tray. Next, install the new battery tray instead.
The new battery pack must be soldered in the manner shown in the following diagram. The white cable in the diagram is for balancing. Cover the battery pack with tape or a shrinking tube.
Once your new pack is in place, you can close the radio again. Make sure that the 21700 pack is inserted into the radio before you close the radio. The 21700 pack will not fit through the standard battery lid.