Hi, everybody. This is my first post, hope it's not dumb. I cut the secondary windings off a microwave oven transformer and wound enough for my DIY uninteruptible power supply, I want between 13 and 14 volts. But with the transformer wound for 13 or 13.5 volts ( I can't remember the exact voltage, I changed the windings a lot ) when I hook it up to the battery/inverter the voltage jumps up to 14, 15, 16 volts. It made me think of a little voltage doubler circuit I played with a few weeks back, I think it's called a charge pump, so I removed the two 15000 microfarad caps I had in there for smoothing but this does no good. What is this phenomenon that has me pulling my hair out? Incidentally, I tried it without the inverter with the same result. Thanks ahead of time.