Inverter trouble???

[Birdmmjb]

I'm having a problem with my solar system.  Right now I have 195 watts of solar hooked up to 4 new 125 ah batteries controled by a sunup charge controler.  The output of the controler I have connected to a bus bar system.  

Now the problems.

1. The controler shuts off power to the buss bar every time I try to connect any other device to the bus when the inverter is connected (700 watt Victor) even when the inverter is off and there is no load on the other devices.
   
2. Yesterday I was able to power the computer with the inverter but today when I power up the inverter I get nothing while the computer is pluged in.  If I unplug the computer shut down the inverter and restart I can plug in a small radio and it will run if I plug in the computer the inverter shuts down.  I don't get it there is not much draw with the tower shut down. I just had a stray thought I had been using the computer on grid before I changed to the solar setup could the electronics being warm from use case this?
   
3. The controler is showing a different charge level than I get with a volt meter when the system is actually working.  IE yesterday when the computer was on the system the volt meters showed a bank reading of 12.6 but the controler showed 13.8 and was shutting of the imput from the solar bank. When the draw on the system is smaller the readings are very close.
   
   

Any Imput as the the case of my problems would be helpfull.

Jan

[Birdmmjb]

Well I pluged the computer into the inverter after my post and guess what it is now working on the inverter.  I don't get it.

Jan

[ghurd]

Do you have a link for the a sunup charge controller?

Sounds like many of the wires are way too small.

G-

[Volvo farmer]

I have an idea. I've seen the same type of behavior on my mini-system.

Is it possible that the inverter is shutting down on over-voltage with the batteries at  13.8V? Mine has done this before, especially when batteries are very cold and the C40's temp compensation pushes absorb voltage pretty high. Maybe load the batteries a little with a DC load to see if it fixes things, either that or turn down that charge controller.

[bob golding]

tend to agree with volvo farmer that it is in going into overvoltage shutdown. usually all the small inverters i have come across shut down at 15 volts. the other thing could be an earth loop somewhere. try to arrange all the grounds to go to one place. dont know for sure but might be worth checking.

cheers

bob golding

[Birdmmjb]

G sorry I dont have a link for the controler I purchased it off e-bay and received almost no information with it when it arrived.

Volvo all the wiring from the solar panels and the battery bank is 12 gage wire.  I have enough of it to double if that is the problem. But with the sometimes it works and sometimes it doesent gives me fits.  If it did the same thing each time it would make it easyer to guess what the problem is but it's different each day or seems so.

My biggest worry at this time is that I'm afraid that my new battery bank is being undercharged all the time.  I have a dump load controler I purchased earler this year but still have not built a dump load for it.  Yesterday I took apart one of the electric tea pots I found on a dump run and was playing with the heat coil its rated at 750 watts 120v ac when hooked to the wind mill it gets quite warm could this be used as a dump load in some mannor.  Thinking about mounting it to a brick and just letting it heat air.

Jan

[ghurd]

If the controller is showing 13.8V and shutting down, while the battery shows 12.6V, then the current in the wire has a large loss.

The wires are too small.

Feeding a 700W inverter to a computer with #12 is far too small.

The tea pot won't dump much power.

At 120V, 750W is 6.25 ohms.

With 12V (14.2V), 6.25 ohms will only dump 2.27A. 2.27A at 14.2V is only 32W.

G-

[Birdmmjb]

G would doubling the 12 ga wire help with this situation?  I found 200 feet of 12 ga cheep and thought it would be a great improvement from the 16 ga I started the system with.

I would understand that I have large losses from the solar panels to the controler as it is a 70 foot run but from the controler to the battery bank is only 3 feet and only 6 inches from the controler to the bus bar. I guess I still don't understand the wire size charts.

Jan

[scottsAI]

Hello Birdmmjb,

Unfortunately so many details are missing it is difficult to help.

Take a look: (wire loss calculator)

http://www.powerstream.com/Wire_Size.htm

If you use copper wire, 12 gage, 20 feet long, 15 amp load (computer+mon = 200w)

The voltage drop is 1 volt as seen by the inverter.

The distance is the wire length from the battery to the inverter.

"controller shuts off power to the buss bar every time I try to connect..."

Is the controller supplying the loads to the inverter? Is it rated for 60amps?

(700w/12v = 60amps)

You mention 70 feet, 200w solar panels to battery with 12 gage = 3.428 volts drop. The panels must generate 13.8v + 3.4v or 17.2v at full power to fully charge the batteries, this is on the edge of most panels, I expect your system charging efficiencies is on the low side.

Please provide a wiring diagram showing physical lengths of wire and gage. What does the controller do, include how it's wired in!

Have fun,

Scott.

[fungus]

"The tea pot won't dump much power.

At 120V, 750W is 6.25 ohms.

With 12V (14.2V), 6.25 ohms will only dump 2.27A. 2.27A at 14.2V is only 32W."

Little mistake? ..

At 120v, 750W is 6.25 A , 19.2 ohms. At 14.1v that would be 0.73A and 10.4W.

[ghurd]

"from the controler to the battery bank is only 3 feet"

And

"only 6 inches from the controler to the bus bar"  

The bus bar is fed through the controller?  The controller has LVD or load connections?  Don't use it.

Feed the inverter straight off the battery.

From the battery to the back of the inverter is over 3.5 feet of #12? Then more wire from the bus bar to the inverter?

Probably want #6 at least, and keep the inverter close to the battery.

I like keeping the Charging separate from the Load.

Fungus is right about the tea pot.  I hate it when that happens.  ;-)

G-

[Birdmmjb]

Second try to post system layout.

Sorry not a very good drawing.

Jan

[ghurd]

Yea, the losses from the battery to the inverter are too much.

Not just the wire loss in the shown #12, but from the bus bar to the inverter and the controller has semiconductor losses in between.

That doesn't explain why the controller would show 13.8V while the battery was at 12.6V.  Might double check the connections with a volt meter.

G-

[scottsAI]

Birdmmjb,

I have my doubts about the controller. Not rated for full load of inverter.

Connect the inverter directly to the battery.

Most inverters will shutdown on low voltage, making the controller redundant.

Keep the other loads connected to the controller.

Your wire is thinner than I would use, but its what you have. Lengths are short, making the above changes should allow it to work.

Have fun,

Scott.