You should learn this for better Asus Zenbook UX303LN battery performance

Before you use your Notebook PC on the road, you will have to charge the battery pack. The battery pack begins to charge as soon as the Notebook PC is connected to external power using the power adapter. Fully charge the battery pack before using it for the first time. A new battery pack must completely charge before theNotebook PC is disconnected from external power. It takes a few hours to fully charge the ASUS battery when the Notebook PC is turned OFF and may take twice the time when the Notebook PC is turnedON. The battery status indicator on the Notebook PC turns OFF when the battery pack is charged.

Original ASUS ZenBook UX303LN Series 11.31V 4400mAh laptop batteries

The battery starts charging when the charge remaining in the battery drops below 95%. This prevents the battery from charging frequently. Minimizing the recharge cycles helpsprolong battery life.

The battery stops charging if the temperature is too high or the battery voltage is too high.

WARNING! DO NOT leave the battery pack discharged. The battery pack will discharge over time. If not using a battery pack,it must continued to be charged every three months to extendrecovery capacity or else it may fail to charge in the future.

Source from Internet.