Inverter output voltage low

[John D3181]

I have a new Cobra 2575, 2500 watt (modified sine wave) inverter. When I check the output voltage with two different digital meters, I get a reading of 85 volts. Is this a faulty inverter or is the reading due to manner in which my meters measure the AC current?

 

[sailingdog]

A 2500 Watt inverter requires A LOT of current... what size battery bank is it connected to and what size wire did you use to make the connection. At full draw, the Cobra will require upwards of 200 amps... (2500 watts / 12 Volts = 208.33) and that isn't even accounting for any losses in the conversion process.

I'd also be wary of using an inverter of that design on a boat... since you don't have any GFI protection, which you would probably have on an inverter with AC outlets that were wired into the boat, making the risk of electrocution far higher.

Also, that inverter doesn't appear to be a marinized model, and is probably more easily subject to corrosion from the high humidity/moisture of a marine environment. Corrosion in the unit can cause serious problems.

 

[Dave from Mi]

Inverter

Hi John;

In the instructions I got with my Xantrex inverter, they warn of different readings with inexpensive meters. It has to do with the modified sine wave of the inverter. If memory serves me right, that is about the reading I got and it equated to 117 volts by their conversion formula. You might check the Xantrex site for the conversion table. Mine is on the boat 200 miles away.

Fair winds
Dave

 

[Don12364]

OK

An 83 v peak square wave delivers the equivalent AC power to a 117 v RMS sine wave. The extra couple of volts you see on your meter are probably due to the 'modified' part of the wave in generating approx 165 v peak so that equipment with inbuilt DC power supplies gets the correct voltage.
If you were to measure it on a 'True RMS meter' it would probably read 117 v.
Try running a lead lamp from the inverter and again from conventional mains (shore power) if the filament looks approximately as bright from either source it would be a reasonable assumption that the inverter is okay.

 

[John D3181]

Thanks for the replies. I was assuming that a true RMS meter would have given me a better reading but I needed some assurance. I've since put a 1500 watt resistive load on the inverter and it seems to perform very well.

 

[John D3181]

Sailingdog, thanks for your concern, but all of the issues you address have been taken care of.