Battery Capacity Gauge is an indicator of battery life. This is used in electric powered trucks.

A battery charger is a device used to put energy into a cell or (rechargeable) battery by forcing an electric current through it. The charge current depends upon the technology and capacity of the battery being charged. This device is plugged into an electrical outlet and connected to the two terminals of the battery to restore the state of charge in the battery. One of the leads coming from the charger is red and the other is black. The red lead is clamped on the positive post of the battery while the other is clamped on the frame of the vehicle. There are different types of battery chargers they are simple chargers, timer based chargers, intelligent chargers and USB based chargers.