Einhell Power X-change 18v 2 X 4.0ah Li-ion Twin Pack Battery

From the power tools batteries & chargers range:

The Einhell PXC Twin Pack 18V 4.0Ah Li-ion batteries are part of Power X-Change One Battery Fits All System. The Power X-Change rechargeable batteries can be used universally for supplying power and endurance to every cordless tool from the entire garden and workshop product family. A single rechargeable battery and a single charger for all tools not only saves significant costs but helps protect the environment and provides flexibility in the home and garden too. It also eliminates the untidiness and chaos of having different rechargeable batteries and chargers for each separate tool. With 2 x 4.0Ah batteries the working time will be longer and the batteries can provide more power for power demanding applications. The ABS process-controlled active battery management system has a microprocessor for permanent monitoring. It therefore ensures maximum safety optimum tool performance maximum operating time and a maximum service life. The current charge level can be checked on a 3-step LED display.