A powerful battery that delivers performance at a value.For users of AK Series products looking for the next level of performance at a great value, the STIHL AK 20 battery not only delivers double the capacity of the AK 10, but it still features the innovative benefits that make the AK Series of batteries a dependable and high-performing battery-powered option. The AK 20 has a long service life with the ability to withstand 1,500 charge cycles.Run time may vary based charge level and operating style.