Anyone know why my shunt would think that watermaker demand is a charge

[Tim-JS]

Bit of a weird one, and I cant think what's going on.

When our battery monitoring shunt shows that our solar and wind gen are providing a large net amp input to the batteries, we often want to use the "spare" amps to run our 12v watermaker.

When we switch on the watermaker, the battery monitor shunt immediately changes to show even more "spare" amps going in, but the voltage reading on the shunt shows the battery voltage reducing over time.

Anyone know why the shunt thinks the watermaker amps are a charge rather than a load?

Thanks

 

[VicS]

You probably have the watermaker negative connected directly to the battery negative, or battery end of the shunt, rather than to the other end of the shunt or negative bus bar

 

[vas]

What shunt, how is it wired?

 

[Norman_E]

What sort of ammeter? Is it possible that it shows amps regardless of whether it is charging or discharging?

 

[Tim-JS]

Thanks for the speedy responses.
It's a xantrex linkpro, but I cant currently see how it's wired as it's hidden away.
I was hoping that a description of the symptoms would highlight that it could only be a single thing .

Bit more info with an example of the symptoms:
- we have the monitor showing that the solar and wind are producing a consistent excess of 20A
- we turn on the watermaker and the monitor immediately jumps to showing there's a consistent excess of 45A

Thanks again

 

[Tim-JS]

What sort of ammeter? Is it possible that it shows amps regardless of whether it is charging or discharging?

Sorry forgot to answer this one.
It shows negative values when there's more being consumed than produced.
Thx

 

[Tim-JS]

You probably have the watermaker negative connected directly to the battery negative, or battery end of the shunt, rather than to the other end of the shunt or negative bus bar

View attachment 144810

Thx.
If the watermaker neg is connected directly to the battery or the battery end of the shunt, wouldn't that just mean the monitor doesn't have any visibility of it's demand, therefore the amp draw wouldn't change when we switch it on?

Thx

 

[simonfraser]

deleted

 

[PaulRainbow]

You probably have the watermaker negative connected directly to the battery negative, or battery end of the shunt, rather than to the other end of the shunt or negative bus bar

View attachment 144810

That wouldn't show a 25a charge, it just wouldn't register.

 

[VicS]

Thanks for the speedy responses.
It's a xantrex linkpro, but I cant currently see how it's wired as it's hidden away.
I was hoping that a description of the symptoms would highlight that it could only be a single thing .
Bit more info with an example of the symptoms:
- we have the monitor showing that the solar and wind are producing a consistent excess of 20A
- we turn on the watermaker and the monitor immediately jumps to showing there's a consistent excess of 45A

Thanks again

Make sure your watermaker is connected to the main battery positive and battery negative terminals shown in the diagram below NOT to either of the red starred points

Taken from the Xantrex LinkPRO manual and edited:-



But what do you mean by producing "a consistent excess" ? Do you mean that the monitor is showing a charge current of 20A?

.

 

[VicS]

Thx.
If the watermaker neg is connected directly to the battery or the battery end of the shunt, wouldn't that just mean the monitor doesn't have any visibility of it's demand, therefore the amp draw wouldn't change when we switch it on?

Thx

You are right in so far as that the monitor will not see the water maker current except that when the solar and wind gens are producing a charge current, and the battery is well charged, when the water makeris switched on it will take some of its current from the chargers which the Xantrex will see as a charge current. That I am sure is what is happening and that is why no connections should be made to the red starred points .

 

[vas]

Thx.
If the watermaker neg is connected directly to the battery or the battery end of the shunt, wouldn't that just mean the monitor doesn't have any visibility of it's demand, therefore the amp draw wouldn't change when we switch it on?

Thx

only case I could imagine possible is that IF and only IF, the two sources of energy (solar + wind) COULD if fully stretched produce 45A. The reason they are producing 25A is that the "demand" from the batteries/rest of consumption only requires 25A.
So in that case, as soon as you turn on the watermaker, the two sources go in full power mode and produce as much as they possibly can which is 45A and this is registered by the shunt.
Then, yes, this whole thing means that the watermaker is connected to the battery poles and not through the shunt.

So Q: with batteries fairly low full wind and solar, have you ever seen 45A in the shunt? how big are the solar and the wind? how big the battery bank?

V.

DOH! missed VicS post above, sorry saying the same thing...

 

[Tim-JS]

only case I could imagine possible is that IF and only IF, the two sources of energy (solar + wind) COULD if fully stretched produce 45A. The reason they are producing 25A is that the "demand" from the batteries/rest of consumption only requires 25A.
So in that case, as soon as you turn on the watermaker, the two sources go in full power mode and produce as much as they possibly can which is 45A and this is registered by the shunt.
Then, yes, this whole thing means that the watermaker is connected to the battery poles and not through the shunt.

So Q: with batteries fairly low full wind and solar, have you ever seen 45A in the shunt? how big are the solar and the wind? how big the battery bank?

V.

DOH! missed VicS post above, sorry saying the same thing...

Sorry for the delay, lack of WiFi...

We have 1040W of solar and 400W of wind, and regularly see over +60A on the monitor in the morning when the house bank is depleted.

My understanding of what the monitor is showing is the net flow of Amps in (+ve value) or out of (-ve value) the battery bank eg if the solar plus wind are generating 60A but we have cumulative demand of 15A then I expect the monitor to show 45A.

So in my earlier example above, I think solar plus wind was generating approx 45A and our cumulative consumption was around 25A, so the monitor showed +20A.
Then when we turn on the watermaker, which is rated at 27A we see the monitor jump to showing +45A.

It's as if the watermaker motor is wired the wrong way round so that a -25A draw is showing as a +25A charge.

Does this extra info change any of the suggestions above?

Thanks again.

 

[vas]

nope, just verifies what I typed above.
remove the cable going to the watermaker that is between the shunt and battery pole and move it where it should be to be metered: at the other end of the shunt.
As a rule, cable from shunt to battery should be just that. NOTHING to be bolted on the terminal, all loads must be on the "other" side.
nothing wrong, just wrongly wired watermaker. guess 5min job to correct it.

V.

 

[pyrojames]

That wouldn't show a 25a charge, it just wouldn't register.

Isn'it possible that when the Watermaker starts, it'll drop the voltage at the battery, but not register any current flow. The solar controlller will up its input to the battery, and it will appear that the battery is receiving extra charge, although the voltage is most likely dropping.

 

[roaringgirl]

nope, just verifies what I typed above.
remove the cable going to the watermaker that is between the shunt and battery pole and move it where it should be to be metered: at the other end of the shunt.
As a rule, cable from shunt to battery should be just that. NOTHING to be bolted on the terminal, all loads must be on the "other" side.
nothing wrong, just wrongly wired watermaker. guess 5min job to correct it.

V.

My money is on this being the answer - check the negative supply to the watermaker - it isn't going through the shunt.

 

[PaulRainbow]

You are right in so far as that the monitor will not see the water maker current except that when the solar and wind gens are producing a charge current, and the battery is well charged, when the water makeris switched on it will take some of its current from the chargers which the Xantrex will see as a charge current. That I am sure is what is happening and that is why no connections should be made to the red starred points .

Good point. If the solar output was being limited by the batteries being charged, drawing power

nope, just verifies what I typed above.
remove the cable going to the watermaker that is between the shunt and battery pole and move it where it should be to be metered: at the other end of the shunt.
As a rule, cable from shunt to battery should be just that. NOTHING to be bolted on the terminal, all loads must be on the "other" side.
nothing wrong, just wrongly wired watermaker. guess 5min job to correct it.

V.

Given the extra info in #13, i'd say this is correct, as was Vics post #11

 

[VicS]

We have 1040W of solar and 400W of wind, and regularly see over +60A on the monitor in the morning when the house bank is depleted.

So in my earlier example above, I think solar plus wind was generating approx 45A and our cumulative consumption was around 25A, so the monitor showed +20A.
Then when we turn on the watermaker, which is rated at 27A we see the monitor jump to showing +45A.

Isn'it possible that when the Watermaker starts, it'll drop the voltage at the battery, but not register any current flow. The solar controlller will up its input to the battery, and it will appear that the battery is receiving extra charge, although the voltage is most likely dropping.

Hopefully the diagrams below will explain what I am sure is happening


In the first the monitor shows a charge current of 20 amps, the total domestic load is assumed to be 25amps meaning the wind and solar system is delivering 45 amps.

In the second the watermaker is switched on, drawing 27amps, the monitor now shows +45 meaning that the battery charge current has dropped slightly to 18amps.
If the domestic load remains at 25 amps it means the wind and solar system will be delivering 70amps ( 25+45)

Finally what would be happening with the watermaker connected to the load side of the shunt, assuming the same solar input and the same domestic loads.

The battery charge current remains at 18 amps and this is shown as +18 on the monitor
The watermaker and domestic loads are supplied by the wind and solar system

.

 

[Tim-JS]

Great diagram, I love it.

Hopefully the diagrams below will explain what I am sure is happening

View attachment 144848
In the first the monitor shows a charge current of 20 amps, the total domestic load is assumed to be 25amps meaning the wind and solar system is delivering 45 amps.

In the second the watermaker is switched on, drawing 27amps, the monitor now shows +45 meaning that the battery charge current has dropped slightly to 18amps.
If the domestic load remains at 25 amps it means the wind and solar system will be delivering 70amps ( 25+45)

Finally what would be happening with the watermaker connected to the load side of the shunt, assuming the same solar input and the same domestic loads.
View attachment 144850
The battery charge current remains at 18 amps and this is shown as +18 on the monitor
The watermaker and domestic loads are supplied by the wind and solar system

.

Thanks for the thorough explanation

Hopefully the diagrams below will explain what I am sure is happening

View attachment 144848
In the first the monitor shows a charge current of 20 amps, the total domestic load is assumed to be 25amps meaning the wind and solar system is delivering 45 amps.

In the second the watermaker is switched on, drawing 27amps, the monitor now shows +45 meaning that the battery charge current has dropped slightly to 18amps.
If the domestic load remains at 25 amps it means the wind and solar system will be delivering 70amps ( 25+45)

Finally what would be happening with the watermaker connected to the load side of the shunt, assuming the same solar input and the same domestic loads.
View attachment 144850
The battery charge current remains at 18 amps and this is shown as +18 on the monitor
The watermaker and domestic loads are supplied by the wind and solar system

.

Great diagram, I love it.

Thanks for the comprehensive and clear explanation.

Cheers, Tim

 

[Tim-JS]

Apologies for the delayed update but have been without connectivity, and thanks for all the advice.

As suggested, the negative of the watermaker was indeed attached directly to one of the batteries in the house bank.
We eventually managed to mouse it through to where the shunt is located and hey presto, now when we turn on the watermaker the shunt correctly sees this as demand.

Thanks again everyone for the help.