I feel this is a very simple question, but I can't seem to wrap my head around it. For example, if you have two 1.5 volt batteries in series and a load of 100 ohms then the total voltage is 3 volts and the current is 30mA because I=V/R. If you have two 1.5 volt batteries in parallel then the total voltage is 1.5 volts and the current is doubled so if you have a 100 ohm load then each battery supplies 15mA and the total current is still 30mA, right? I've read a lot of posts discussing how series increases voltage and parallel increases current, but that's with an open circuit. When you connect a load doesn't it all amount to the same current being delivered in the end despite the difference in voltage? I guess I don't understand the benefit or advantage of the different set ups.