Originally Posted by Ness
No, two 1.5v batteries won't make 3v; it will still equal 1.5v if I remember correctly from the two week electrical unit from grade 9 Science class that I took 5 years ago. I believe you need to add amplifiers to increase the voltage of a battery.
Read what Maza said, everything you need to know is in the guide found on the link provided.
Two 1.5v batteries in series, i.e. ---[battery]--[battery]--- will make 3 volts. If the two batteries are wired in parallel, then the voltage will stay at 1.5v.