The MegaLife is sensitive about chargers. Use the 5V/1A charging cube that came with your phone — it's a low-wattage cube on purpose. Many modern fast-charging cubes (like the ones that come with iPhones or newer Samsungs) are not compatible with the MegaLife and can cause poor charging or rapid battery drain.
If you've lost the original cube, any standard 5V/1A USB cube should work. If you're still having battery issues with the right charger, use the Feedback option inside the MegaLife app to report it directly to the developers — they actively read those reports.