Battery level on battery indicator drops when i connect a load?
This indicator is working by watching the voltage across the meter, and that's all it is doing. A battery's voltage decreases as it discharges, so the voltage gives you a rough measurement of the charge level.

However the voltage also decreases depending on the amount of current being taken from the battery. This effect is greater (more decrease) on smaller batteries.

A charger is like the opposite of a load. It pushes current the other way through the battery, which causes it to charge and which causes the voltage to rise above the normal battery voltage.