I just watched the Deconstructed episode that was talking about lead acid batteries for cars and I would like somebody at that show or the Science Channel explain how a car alternator and or the lead acid battery can magically change the flow of electrons in a Direct Current battery system. The narrator states that when the car starts the alternator all of a sudden puts the charge into the battery by all of a sudden forcing the electrons/current back into the negative side of the battery, I am sorry but DIRECT Current only goes one direction and that is from Negative to Positive and if the people in your show have a problem with that then get them an inductive ammeter that has a scale that will go in either direction and when you put it on any wire in the automotive charging/electrical system it will show you which way the power is flowing. It is hard enough a lot of the time convincing people that the power in an automotive electrical system or any DC system that the power flows from the Negative to the Positive as it is and then you have a show on global television saying that you can magically change the flow of electrons and reverse that flow, let alone that how WONDEROUS the acid in the battery is in that it will allow the flow of Direct Current to change direction when the car starts, and that the rest of the car would even still run when you changed the direction of the current. I now really wonder about the validity of the rest of your research on any of the segments of Deconstructed. I must say that I am really disappointed in the researchers for the Deconstructed show, partly because this isn't the first time they have been wrong about something but more so that they would get something as simple as how a car battery and charging system actually work. Please do everyone that watches this show and the Science Channel in general a favor do the research before doing the show. As far as I am concerned your credibility on some of these shows is waning because of these mistakes, I would think that you have a responsibility to the viewing public to get the facts before putting a show together and not misinforming people.

You are corect in the fact the electrons flow in one direction but you are stating one theory of electron flow there is conventional theroey which positive to negative and electron theory which is negative to positive.

The alternator isn't pure DC but a pulsed square wave, and also typically runs about 2 volts more than the battery its charging. Basic Ohms law dictates that the higher voltage will "control" the circuit and in effect make the current flow the other way at the battery. It's not a question of reversing flow as much as dealing with a higher voltage.

Last I knew, an alternator puts out 3 phase AC that is then sent to a set of diodes to get the DC, it is not a square wave. The output voltage is set by the voltage regulator.