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I have just transferred my 300W solar system to the new boat.  I have one of these to monitor the output from the Victron 75/15 mppt controller ...  https://www.droking.com/2in1-digital-voltmeter-ammeter-dc-100v-50a-digital-tester-red-led-display-volt-amp-meter-dc-6v-12v-24v-voltage-monitor-with-shunt-resistance

 

it has been wired up as shown on the website.

 

previously the set up worked fine.  in the new boat, with bright cloudy skies, the ammeter is reading and 14A, but a check using the clamp meter shows 0.33A which is about what I would expect.  (the voltmeter is at 12.9V).  

 

so a discrepancy of x40 .................................... any ideas?

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My ammeter, Chinese digital cheapo, has a shunt wired alongside it, could that be anything? 

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32 minutes ago, Murflynn said:

it has been wired up as shown on the website.

I can’t see that. Where is it?

 

First thoughts are power being taken from wrong side of the shunt but without viewing the diagram that’s only a guess. 

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the multiple photos include, if you scroll right, 3 options for wiring. 

I used option 2 with the 'device' being the battery bank and the 'battery power supply' being the solar panels.  

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I can't see the diagram either

Just found a diagram - its on the UK Amazon site  But confusing with motors and controller things on the diagram

Edited by Tony Brooks

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19 minutes ago, Murflynn said:

I used option 2 with the 'device' being the battery bank and the 'battery power supply' being the solar panels.  

Move the power supply to the top of the battery. Don’t think about sharing the power supply and PW+ feeds down one wire, they must be kept separate. 

19 minutes ago, Tony Brooks said:

confusing with motors and controller things on the diagram

Agreed. It needs drawing properly to make sense. 

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13 minutes ago, WotEver said:

Move the power supply to the top of the battery. Don’t think about sharing the power supply and PW+ feeds down one wire, they must be kept separate. 

Agreed. 

The battery connections are made to the negative bus and to the positive stud of the isolating switch; I believe the tapping shown on the diagram is just to make sure the supply voltage is between the stated limits.

 

Maybe I should I treat the battery as the supply side and the MPPT controller output as the load; I guess I was over-thinking it when I did it the other way, as I described above.  Would that make any difference?

 

Why would those 2 leads be kept separate? They are connected to the same terminal, so should both be about 12.9V.

Edited by Murflynn

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2 minutes ago, Murflynn said:

why would those 2 leads be kept separate? They are connected to the same terminal, so should both be about 12.9V.

Because any load taken by the display will cause a slight volt drop down the cable. As the voltage on the cable is being used to determine the current you don’t want that. 

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4 minutes ago, Murflynn said:

maybe I should I treat the battery as the supply side and the MPPT controller output as the load; I guess I was over-thinking it when I did it the other way, as I described above.  Would that make any difference?

Yes. :)

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