The Think Pad 28++ 9 cell battery can serve as a more powerful replacement for your standard T or W series notebook battery. These 94 Wh rechargeable batteries use Lithium-Ion technology & can serve as replacements for ageing system batteries. You could also use the Thinkpad 28++ battery as a convenient spare battery, to keep on hand when you need to keep your system powered for several hours on end. This Thinkpad battery is compatible with T410/20/30, T510/20/30 & W510/20/30 series notebooks. It is compatible with the Think Pad External Battery Charger & connection via a docking port Lithium-Ion (Li-Ion) technology 9 cell slice secondary battery attached to bottom of system Connection via docking port Battery energy (Watt-hours): 94 Wh Mechanical On/ Off indicator