Inverter out going voltage - Low

[alan0043]

Hi Everyone,

 

I have been working on the inside of the truck trying to get ready for the ECR this year. The last piece of the puzzle was to put the inverter back into the truck. I never turned on the inverter to see if it ever work correct even though I have had the truck for awhile. I am getting to my problem. I have everything hooked up. I even have new cables (welding cables) coming from the batteries. I checked the out going voltage and found out I have only 90 vac. The truck batteries are at 12.7 vdc. I thought that may be the truck needed to be running. When the truck is running, it is putting out 13.8 vdc but the inverter is still only putting out 90 vac. I am bummed out.

 

Is this a common problem with inverters ? The inverter is a Cobra 1500. Can it be repaired ? Do you need to do bench testing to find the problem ? Is it worth the cost of repair ? Is there anyone going to the ECR this year that is familiar with the insides of an inverter ? I wish I was back working so I could see the guys in the electronics lab. Is this some work that can be done at home ?

 

Thanks for any help,

Al

[Nuke-E]

Hi Al,

 

If that's a modified sine wave inverter, most meters won't read correctly. The average voltmeter just looks at the peak voltage (~155-170V) , and divides by sqrt(2) to give you an RMS reading (~110-120V). With a modified sine wave, the ratio between the peak voltage and the RMS voltage is no longer sqrt(2). If you can get your hands on one, take a look at it with a true RMS meter.

 

I don't want to suggest nothing is wrong, but that you make sure there is something wrong before you go out and spend money.

 

David

[Jack Mayer]

David has it pegged. This would be typical behavior under those conditions. Get the right meter and you will see if you really have an issue. With 12.7 input voltage you should be good. Or, you can plug a dropcord lamp into it and see if the light is it's normal brightness (incandescent bulb). If it is, then I'd say you do not have an issue.

[alan0043]

Hi Al,

 

If that's a modified sine wave inverter, most meters won't read correctly. The average voltmeter just looks at the peak voltage (~155-170V) , and divides by sqrt(2) to give you an RMS reading (~110-120V). With a modified sine wave, the ratio between the peak voltage and the RMS voltage is no longer sqrt(2). If you can get your hands on one, take a look at it with a true RMS meter.

 

I don't want to suggest nothing is wrong, but that you make sure there is something wrong before you go out and spend money.

 

David

 

Hi David,

 

The inverter is a modified sine wave inverter. I will try to find a RMS meter. I will report back later after I can find the right meter.

 

Thanks for the help,

Al

[RickS]

I purchased this many years ago and has been very good Extech EX623. I use it a lot to take tire, wheel, and hub temperatures when I'm traveling. It was not cheap but liked the multi functional aspect.

[ray.service]

I purchased this many years ago and has been very good Extech EX623. I use it a lot to take tire, wheel, and hub temperatures when I'm traveling. It was not cheap but liked the multi functional aspect.

http://www.lowes.com/pd_464288-295-21050T_0__?productId=50125831

About 1/2 the price of the Extech w/o the IR. Almost same functions. In a head to head with my Flukes the accuracy is very good.

BTW. Southwire is a large wire and cable mfg in Carrollton, GA. Not sure why they "self branded" meters.

[alan0043]

Hi Everyone,

 

I have a new number to report on the inverter. A friend of mine stopped over at the house with his Fluke. The new number is 111 vdc coming out. I hope this good enough to run a refrigerator or a microwave. It is nice to have the right tool for the job. I am still learning. Thanks for telling me about the meter. I forgot about the inverter being a modified sine wave.

 

Al

[Jack Mayer]

You are good-to-go with 111volts, Al.

[alan0043]

You are good-to-go with 111volts, Al.

 

Thanks Jack. I feel better now.

 

Al