A battery pack is a collection of multiple batteries that are connected together to provide a higher voltage or capacity than a single battery can offer. These packs are commonly used in various devices, such as electric vehicles, smartphones, and laptops, to store and supply electrical energy. Battery packs can be made from different types of batteries, including lithium-ion, nickel-metal hydride, and lead-acid. They are designed to be rechargeable and can power devices for extended periods, making them essential for modern technology and renewable energy systems.