Bosch's GBA18V40 CORE18V 4.0 Ah battery uses 21700 Lithuim-ion cell technology to offer the capability of the original CORE battery in a smaller, lighter package. Bosch says the new cell introduces more active battery volume in a pack that’s only slightly larger than the previous 20700 cell packs. The Bosch design allows the power cells to be arranged in a single layer, and features Bosch's CoolPack 2.0 technology, which the company says delivers up to 135 percent longer life than other conventional batteries. The battery is also designed without space gaps, which ensures any heat produced by the cells is not stored in the interior.