Insufficient support of electric current sensing on commodity mobile devices leads to inaccurate estimation of their Battery's state-of-health (SoH), which, in turn, shuts them off unexpectedly and accelerates their Battery fading. In this paper, we design V-BASH, a new Battery SoH estimation method based only on their voltages and is compatible to commodity mobile devices. V-BASH is inspired by the physical phenomenon that the relaxing Battery voltages correlate to Battery SoH. Moreover, it is enabled on mobile devices with a common usage pattern of most users frequently taking a long time to charge their devices. The design of V-BASH is guided by 2; 781 empirically collected relaxing voltage traces with 19 mobile device batteries. We evaluate V-BASH using both laboratory experiments and field tests on mobile devices, showing a <6% error in SoH estimation.