Rubik's cube Robot solver

Hi Kas

I am slowly assembling what is needed for this project. What do you think about this as a power supply:

https://www.ebay.co.uk/itm/Waterproof-18650-Battery-Pack-8-4V-Case-House-Cover-for-Bike-Light-Lamp-UK-stock/282920287390?hash=item41df5cfc9e%3Am%3Am5OE9_yJ4FOGiJXL5Qt36zw&var=582770477611&_pgn=2&_sacat=7294&_nkw=bike+light+battery+pack&_from=R40&rt=nc

8.4 V to power the Arduino, 5 V to power the servos.

By the way I am heading for the Android route. Any chance that I can have the app now in readiness?

Thanks.