Slendertone Optimum switches off during a toning session? Recharge the batteries for 3 hours, once charged start your toning session again. If the problem persists please contact us. Related articles What happens if I connect the coloured leads incorrectly? What if my battery dies during a session? Slendertone Optimum Set Up Video Contact Us The controller does not switch on when the Power button is pressed Comments 0 comments Please sign in to leave a comment.