Enchanted accuses Duracell’s “Powerbank” of infringing U.S. Patent 6,194,871, directed to charge and discharge control circuits for secondary batteries that prevent overcharge and overdischarge of the batteries. According to the complaint, the patented technology solves the problem of preventing a battery from being erroneously charged by another battery pack connected in parallel while also permitting recharge of a battery even when the voltage is completely discharged. The Powerbank products are portable chargers for USB devices and smartphones, and Duracell lists overcharge protection as one of the Powerbank’s safety features. Enchanted, a Plano, Texas corporation (and thus presumptively a Non-Practicing Entity), extensively pleads personal jurisdiction, based on Duracell’s having a principal place of business in Massachusetts, regularly conducting business and deriving substantial revenue in Massachusetts, offering products online to customers in Massachusetts, systematically conducting business in Massachusetts (including the accused activities), and having a regular and established presence in the district. The patent has changed hands a number of times, and was last assigned to Enchanted by Huawei Technologies. Enchanted seeks injunctive relief as well as monetary damages; injunctive relief may be hard to come by, however, as the patent claims priority to a December 3, 1999 Japanese application and will thus almost certainly expire prior to a decision in the litigation.