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.
After I finished the new battery pack, I took the opportunity to cycle (full charge, full discharge and full charge again) both, the old and the new battery pack. The results show an increase in available capacity of about 60%. I am expecting a few additional hours of radio usage with one charge. The previously used 2s 18650 with a nominal capacity of 3400 mAh had a disappointing 2515 mAh of available capacity. The new 2s 21700 pack with a nominal capacity of 5000 mAh has an available capacity of 4165 mAh. These figures are likely to be different for every pack and dependent on your charge’s cycling settings. But the figures show a pleasant improvement.
You don’t need to worry about charging and balancing the battery pack – the radio takes care of it as it does with the standard 18650 battery. The charging just takes a bit longer due to the larger capacity of the 21700 cells.
To upgrade, you will need:
First, remove the 4 screws on the back panel of the radio and lift the back panel off. Remove the 6 screws of the stock battery tray, then first remove the USB plugboard, then the battery tray. Then install the new battery tray instead.
Now solder the new battery pack as per the diagram below. The white cable in the diagram is for balancing. Use tape or a shrinking tube to cover the pack.
You’re ready to put your new pack in place and close the radio again. Keep in mind that you have to put the 21700 pack into the radio before you close the radio. The 21700 pack won’t fit through the standard battery lid.