OK, I thought it was a galvanic reaction, but it's been a while since chemistry for me
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I remember making batteries in class and calculating the voltages by the metals we used (and stareing at the girls) though maybe I forgot the important part. I knew it had to do with electrons (due to the charges) but I thought they "dropped off" as standard particles of AL, thanks for the correction.
P.S. the battery charger part was a joke!