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The ET-232 will automatically shut off after about 60 minutes of operation.
To reset the timer, simply turn the center mode control to another mode. Then, you can return to the previous mode and enjoy another hour of e-stim.
The internal sealed lead-acid (SLA) battery inside the MK-312BT is designed to last about twice as long as the one inside the original ErosTek ET-312B. The larger capacity requires an overnight charge or longer to reach a full charge, especially after many hours of portable use.
The chart below shows the battery voltage for the various percent charge (%) values displayed during power ON.
The displayed charge % level is more accurate when the MK is powered ON with the AC adapter cable disconnected.
It’s a good idea to connect the AC adapter to the unit in between uses. The internal charging circuit maintains the charge level and prevents over-charging of the battery.
Download [PDF]: MK-312BT Battery Volts vs Percent