Is there a minimum voltage required to charge a 12v lead-acid battery?
You have a lot of interesting but some not so accurate answers. First, the charging voltage on a 12 v battery must be over 12 volts but not way over this. A typical 12 v battert charging circuit, whether it be the car’s alternator or one driven by stationary electrical energy, is designed to run at about 14 volts. A 12 v battery voltage varies a bit with the max full charge slightly over 13 volts. If you apply a DC voltage under the voltage difference of the two battery poles, you will not charge the battery. Therefore 5 volt dc power supply is not going to do the job. Usually a flat DC voltage is not considered best; often a half wave rectified ac signal producing a pulsed DC is preferred for reasons beyond the scope of this fourm. Finally battery chargers that run on stationary electrical energy, whether they be a 120 or 240 v AC circuit takes the energy at supplied voltage and converts it to a dc voltage of about 14 volts. The circuit to do this is beyond the scope of this fourm but
