Laptops are forever getting smaller and lighter
The weight of an adapter depends on the technology used to reduce household power down to the level needed by your device. Common adapters use a 'transformer' to do this. A popular but older and heavier type of adapter uses a large transformer -- these are often called 'linear' power supplies or just 'transformers.'
Smaller and lighter adapters have become more popular over recent years and use a much smaller version of the transformer. This type is called a 'switched mode' power supply.
No matter which technology is used, adapters can't escape the need for a transformer of some kind. This requirements translates to more weight for devices that need more power.
Some manufacturers offer an alternative adapter unit. If this is not possible, try a computer or electronics store for a universal laptop power supply. Universal power supplies are often less expensive than an 'official' laptop vendor alternative and should be perfectly safe to use, but check the output voltage first -- make sure it matches the figure required by your hardware. If you do go this route, be aware that laptop vendors discourage the use of any unofficial hardware and will probably not honor any warranty, so check first.
What Is a Battery Adapter?
A battery is a type of power supply device capable of operating without a constant connection to a source of electricity. Batteries require a specific voltage type to function, which can be provided via a battery adapter.
Definition
A battery adapter is a power supply that converts one form of voltage, called alternating current (AC) to direct current (DC) in order to send the required charge to the battery unit. A battery adapter is also referred to as an AC adapter or charger.
Rectification
A battery adapter rectifies alternating current voltage input to obtain direct current voltage. Rectification is the process of converting AC current, which reverses direction, into DC current, which flows in one direction.
Process
AC current contains positive and negative polarity, which enable the currents to change direction. The rectification process forces these polarities into one direction via the use of diodes in order to output direct current. Diodes are electronic components that enable electrical current to flow in one direction and block current moving in the opposite direction.