Both the DELL Alienware 17 R2 and R3 have a 6-cell lithium-ion battery that is designed to provide long-lasting power. The R2 has a battery life of up to 6 hours, while the R3 has a battery life of up to 8 hours. This makes the R3 the clear winner when it comes to battery life, as it is able to run for up to 2 hours longer than the R2.