[retrosmith]

I understand that through chemical half-reactions an abundance of electrons are amassed at the negative terminal of a battery and a deficit of electrons at the positive terminal. I also understand that you can connect two batteries in series to double the voltage. However, when the batteries are touching at their terminals, but before a circuit is completed, what is happening at the touching terminals? What is keeping the electrons from simply flowing from the negative terminal of the battery into the positive terminal of the other that it is in contact with?

Wouldn’t the electrons flow into the positive terminal of the other battery discharging it until it uses up all of its excess electrons? This would create one battery full of electrons and another of positive charge. Clearly this is not the case, but what prevents this from happening?

[Borek]

Have you tried to calculate "abundance of electrons" necessary to create 1.5V potential difference on the battery terminals? How do they relate to the the battery capacity?

[vmelkon]

You could just ask the same question for non batteries as well. We know that we can rub one material on another and some electrons are pulled from material A and onto material B. But how many electrons are pulled off? Why can't you pull off 50% of the valence electrons or 75% or 100%? Would more rubbing solve that problem?