Need a battery for Averatec Laptops/Notebooks with the following model numbers: 2100 series? BTI has you covered with our premium 4 cell LiIon battery. This product has been engineered to meet or exceed the original manufacturer's specifications and replaces the original Averatec part numbers 957-N0111P-005,BTY-S11,BTY-S12,NA203110-01. All BTI batteries are manufactured and tested under our stringent quality standards and come with an industry leading 18 month manufacturer's warranty. BTI.. True to the Original.