Longer life and better charge capacity with this ‘fit and forget’ device. Simply connect to the + and - terminals and this compact device will help prevent sulphation of the plates which is usually the undoing of most lead/acid batteries. Even promotes better performance from old tired batteries. Internal controls switch the refresher on and off automatically. Suitable for 12V batteries up to 300Ah in cars, trucks, caravans and especially boats. Switches on at 12.6V +/- 0.2V.