This HP replacement battery pack is a 4400mAh, 10.8, rechargeable, removable, Li-ion battery designed to work with HP EliteBook 820 G2-N9N91US. The Hi-Quality battery meets or exceeds original manufacturer specifications for the HP EliteBook 820 G2-N9N91US Laptop Battery in quality, durability, and performance. Li-ion batteries do not suffer from the memory effect. They generally last between 300-500 charge/discharge cycles. All laptop batteries are tested for 100% quality control assurance. This battery for HP EliteBook 820 G2-N9N91US includes a one year warranty. We offer a 30 day money back guarantee and fast shipping on all of our products.