Solar.... getting volts but no amps????

Captain Larry-DH · Jul 20, 2020

Ron20324 said:
I have 2 switches to change the panels from series to parallel. If a panel goes bad, switch to parallel to use just the one good one.

I use a terminal strip, so i can make the change there, and that was useful when I had multiple panels on a controller. Now I have a controller for each panel.

rgranger · Jul 21, 2020

NYSail said:
There is voltage going to the battery. Today I will turn off all loads and see what is coming through in regards to amps.

Thanks!
Greg

A helpful way of thinking about electric circuits is to use a water system as an analogy.

Voltage would be analogous to the pressure in a pipe.
Amperage would be analogous to the flow of water in the pipe.
Resistance is the diameter of the pipe.

The pressure in a pipe exists regards of the fact that water may be flowing or not. Same is true for voltage. The voltage is the pressure you solar panel is able to provide to your battery. And the battery can be thought of as being analogous to a water tower that stores water at a specific pressure (height) or maybe a bladder tank is also a good analogy for a battery. When you panel is trying to charge the battery, you should think of it as analogous to pumping water into a bladder tank. If the tank is empty, there is no back pressure and the flow (current) will be high. As the tank starts to fill, the back pressure from the tank will slow the current.

In you charging system, you will see the same thing. As your battery gets close to "full" the amperage will slow

Captain Larry-DH · Jul 23, 2020

Is the Xantrex monitor showing negative 5.1A? Doesn't make sense to me.

Captain Larry-DH · Jul 23, 2020

NYSail said:
Yep and the monitor is showing diminishing soc. However with solar turned off and alt running all seems fine.

The solar controller was reading very close to that but it was a + reading? To quote Bugs Bunny- “Screwey, ain’t it?”

Davidasailor26 · Jul 23, 2020

Where was the multimeter connected when you measured 5.25A?

Davidasailor26 · Jul 24, 2020

NYSail said:
On the battery where the solar attaches.......

I presume you mean inline between the positive battery post and the red solar lead? Because the black solar lead goes to the load side of the shunt, not the battery, correct? Which lead from the multimeter was connected to the battery, and which was connected to the panel lead?

Davidasailor26 · Jul 24, 2020

The way you drew the picture has the negative lead coming into the battery side of the shunt, not the load side. If that’s how it’s wired then there’s your problem.

NYSail said:
Both leads from multimeter were on the battery where panel leads eventually lead.

I mean the picture where the multimeter is measuring amps, not volts. If the multimeter were set to amps and connected to opposite battery terminals I’m afraid things would’ve been much more “exciting”

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Captain Larry-DH · Jul 24, 2020

Davidasailor26 said:
The way you drew the picture has the negative lead coming into the battery side of the shunt, not the load side. If that’s how it’s wired then there’s your problem.

Davidasailor26 · Jul 24, 2020

I think we’re getting closer.

NYSail said:
So what if I just took the negative lead from the solar controller and connected it directly to the battery?

According to the picture what you’ve done is electrically equivalent to putting the negative solar lead straight into the battery. You’ll charge the battery just fine, but the monitor doesn’t know about it, because the charge current doesn’t traverse the shunt.

NYSail said:
And this alone would affect the monitors reading on amps only and not volts?

Yes, it would. The monitor reads the battery voltage by measuring the potential between the positive and negative battery posts. So that will be accurate. It measures amps by measuring the the potential from one side of the shunt to another. If the charge current doesn’t go through the shunt then the monitor won’t see that current, so the amps will be inaccurate.

I think you’re thinking of the shunt as a bus, which it is not. On a bus all posts are electrically equivalent. A shunt is a very high capacity, low resistance resistor. You need to have all loads and charging sources on one end of that resistor, and the battery on the other. I’m guessing your alternator is on the load post of the shunt, and you now have the solar on the battery side. Put the solar on the same physical post as the alternator input and then they should both read correctly.

Brian D · Jul 24, 2020

This is the correct way to wire a shunt in the system. Note that the current passes through the shunt and is monitored after the it passes. There is a very low value resistor in the shunt and the monitor senses the voltage drop. The shunt allows high currents to pass without damage. This will monitor the panel's current flow only, not the flow to the house banks or starter banks.

Note: If you get a negative value on the monitor (i.e. -5.53aH) then reverse the leads from the monitor to the shunt.
Note: The monitor is nothing more than a volt meter reading the voltage drop across the shunt resistor.

Ron20324 · Jul 24, 2020

NYSail said:
Light bulb!! Guess what...... problem solved! Again the wonders (and patience) of this group is invaluable! Greg

My theory is, if it USES electricity or MAKES it, it has to pass through the neg shunt.

Hayden Watson · Jul 24, 2020

The ONLY thing that sould be connected to the battery side of the shunt is the battery, period.

Solar.... getting volts but no amps????

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