115VAC, 10Hz, safe for my devices?

I'm pretty well versed on electronics, but this one has me stumped. Power Inverter in a car measures 115V, but only 10Hz. My meter (Kill-a-Watt) tests properly in the house @ 60Hz. The inverter states the output should be 60Hz, so I know it's faulty. All my devices seem to work or charge alright, but are there any known issues with too low a frequency? Theoretically, I think the RMS for a sine wave should be the same no matter the frequency (though I couldn't say how clean of a sine wave it's generating), but it all seems moot since it tests the proper 115V, which I know is an RMS spec. Well, that's theory; anyone know practice?