On Thu, 9 Jul 2015 02:47:20 -0700 (PDT), robobass
wrote:

I know this is a metalworking site, but there is quite a bit of expertise on subjects like this here.

I just bought a 200/300Watt 230v inverter. I attached it to a car battery on the bench (nothing else attached) and plugged in a few lamps. The output measured 330v with loads of 50 and 150 watts. The lights did seem brighter, but not excessively so. The voltmeter is a cheapie, but seems generally accurate. I know that these devices produce a modified sinewave, and I should expect a different reading, but I thought the reading should be lower if anything. Is this inverter a dud, or do I just not know how to measure?

Thanks
You should read about 0.7 x the rated voltage on a modified square
wave inverter.