S-8M91 is the replacement battery for SONY QM-91D, compatible with SONY HVR-A1E and DSR-PDX10. S-8M91 can exchange digital info with the cameras, and display remaining power info on the camera viewfinder. With 7.2V nominal voltage, the S-8M91 has 32Wh / 4.5Ah capacity,and can run approx 5.5 hours on SONY HVR-A1 camcorder when LCD monitor is on. The S-8M91 can be charged on SWIT Dual channel charger S-3602M. It takes about 3 hours to charge from empty to 100%.