This thing works fine as long as you don't have a very low battery. When you discharged 12V to 7V, it will accept fully charged 6V and stop charging. I revived my 40 year old SEARS charger (made in USA) and charged the battery to the point where I could start the car and buy a new battery. There should be a switch to allow the charger to deliver 14V to the 12V battery regardless of the voltage sensed, and an internal current limiter to ensure it or the battery does not overheat.
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