Mini inverter?

Question

I bought a mini inverter that is used in a car to converts 12V/ 24V from the car battery to 230 V AC and also having a USB port to provide 5V DC for making use of an USB device.

Before actually inserting it in the cigarette lighter, I connected it to a DC source and checked the output using a digital multi meter.

To my surprise, when a DC 10 V was fed, the USB voltage was 6V, and the power voltage was 505V. when the the input voltage was increased from 10V DC to 20V DC, the USB port still showed 6V, and the power output was 525V. Interesting thing was that in both the cases, if I interchanged the multi meter pins, the voltage at the power outlet was shown as 0V. On the multi meter the range selected was 0-750V AC. Why this is happening? I am afraid to use it in the car fearing that any AC appliance that I use may get damaged as it gives more than 500V, instead of 230V AC.

Answer 1

I loaded a device (a 5 Watts filament bulb that operates on 230V AC. It was just glowing. The voltage was shown as 510V (closed circuit). When I plugged in a 0.5 Watts LED bulb that operates on 230V AC, it did not give any light! The closed circuit voltage was measured as 510V AC. The LED bulb, however, was not damaged. I put a mobile charger for Nokia. It worked. The closed circuit voltage was measured as 510V AC.



There is nothing written on the equipment-absolutely no letter! It is a Chinese make. No technical pamphlet came with it!



I tend to believe that the equipment is fooling my Digital Multimeter. Or else, the devices that I tried would have got damaged.

Answer 2

The unit uses a switching power supply and MUST be loaded for it to operate properly. Read the spec and find where it says MINIMUM current is X A or X mA. for it to operate properly.

Use a resistor of the 230V/xA. to test it for proper output. You may have to use the DUMMY load to get the 5V from the USB port. It may be better to use the car charger for the USB device.

What Brand and Model # is it? Users manual and or Data Sheet is probably on line.

Answer 3

I'm going to agree with Roderick, here: you could be seeing "no load" values. Your inverter is also probably producing a "modified square wave" AC waveform, instead of a pure sine wave. That could be fooling your multimeter.

Answer 4

Try putting something expendable like a small night-light across the output. Does the output drop to 230 VAC? It could be just a cheap design that doesn't regulate well with no load.