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Ammeter wiring


Ray T

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I've done a search both on the 'net and here, the more I search the more confused I get.

 

I have this simple analogue meter, already fitted with a shunt. 

It seems I have the choice to used it to monitor the starter circuit or the domestic. As I don't want to fit two meters which is the better circuit to monitor?

I have found the attached wiring diagram which apart from 6v batteries would appear to be relevant for a boat?

If I chose to monitor the starter battery how do I identify the relay in the circuit and which contact do I connect to?

On the back of the meter the contacts are coloured red and black. Using conventional colour coding I take it RED is to +ve and BLACK is to -ve?

 

Thank you.

 

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david1.jpg

Edited by Ray T
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My suggestion would be don’t use it, sorry. Long charging cables from alternator to ammeter then from ammeter to battery, plus it’s probably only a very low capacity - what’s the reading on the scale?

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Is it that you happen to have this ammeter and you want to use it, or that you want an ammeter and this is one you already have lying around?

If the former, as it is not going to be very easy to read accurately, I would suggest it goes on the starter battery, though I think you will need decent cables especially if it is a long run.

If the latter, I would suggest a quick search on ebay that will find you digital ammeters that can read in both directions and that use very large shunts on the battery negatives - just an extra link cable required for each, and you could by a pair of meters - one for each battery bank.

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19 minutes ago, WotEver said:

Do you have an inverter? Or any other heavy loads?

An Victron energy Pheonix 12/1200 

image.png.78291f7a2a808d4f2161f12bf9ab1bd4.png

12 minutes ago, Johny London said:

Is it that you happen to have this ammeter and you want to use it, or that you want an ammeter and this is one you already have lying around?

If the former, as it is not going to be very easy to read accurately, I would suggest it goes on the starter battery, though I think you will need decent cables especially if it is a long run.

If the latter, I would suggest a quick search on ebay that will find you digital ammeters that can read in both directions and that use very large shunts on the battery negatives - just an extra link cable required for each, and you could by a pair of meters - one for each battery bank.

It is one I happen to have lying around. One issue is I have already drilled a hole for it! It wouldn't be a long run, 2-3 metres at the most.

Edited by Ray T
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3 metres is quite a long run, but if you like the meter, then have it! Being brass I presume you have a kind of traditional aesthetic going on and the added instrumentation would be pleasant. For my money it would go on the starter battery, what do others think? Use good cable and put it in that convoluted trunking stuff as well?

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25 minutes ago, Ray T said:

It is one I happen to have lying around. One issue is I have already drilled a hole for it! It wouldn't be a long run, 2-3 metres at the most.

If the inverter is 'in the line' where the ammeter is then you will have problems.

 

The inverter will be taking 120 amps, ammeter is only 60 amps

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20 minutes ago, Alan de Enfield said:

If the inverter is 'in the line' where the ammeter is then you will have problems.

 

The inverter will be taking 120 amps, ammeter is only 60 amps

That answers one question, thank you. The starter battery circuit it is.

Edited by Ray T
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This may seem a bit daft, however, given that you now have  a hole drilled / cut - how's about:-

removing / disabling the inbuilt shunt and finding  equivalent  external shunt(s) -

mount these near the appropriate batteries, with thin(er)  cables to the instrument panel via a changeover switch.

 

That gives you -

  • a solution to the long lead / voltage drop issue
  • a choice of monitoring both battery banks
  • something nice with which to fill the hole
  • 'Job satisfaction'

I suspect that it's not impossible to find out what the sensitivity of the meter movement is and once done to construct a simple resistor arrangement to give you the appropriate meter deflection. There's no magic involved...

 

 

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I can see very very little benefit in putting an ammeter in the charging circuit of just the starter battery.

With a modern diesel very little gets taken out of a starter battery when you start the engine, so there is very little to put back.  I doubt that meter will read very much at all all in normal circumstances.

Also it is designed to measure in both directions, charge and discharge, but used just to monitor a charging current it will only ever move to the right, and never to the left.

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11 minutes ago, Ray T said:

Thanks to one and all for the information.

If you do decide to use it then I’d remove the shunt from the back of it, fashion a mount for the shunt to be located close to the battery, then run small cables from the shunt to the meter. 

 

Edited by WotEver
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2 hours ago, WotEver said:

If you do decide to use it then I’d remove the shunt from the back of it, fashion a mount for the shunt to be located close to the battery, then run small cables from the shunt to the meter. 

 

 

Indeed, you dont want cables carrying high currents to be any longer than necessary.

 

If one comes loose and shorts against the hull the consequences could be catastrophic.

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On 20/01/2019 at 01:54, Ray T said:

I've done a search both on the 'net and here, the more I search the more confused I get.

 

I have this simple analogue meter, already fitted with a shunt. 

It seems I have the choice to used it to monitor the starter circuit or the domestic. As I don't want to fit two meters which is the better circuit to monitor?

I have found the attached wiring diagram which apart from 6v batteries would appear to be relevant for a boat?

If I chose to monitor the starter battery how do I identify the relay in the circuit and which contact do I connect to?

On the back of the meter the contacts are coloured red and black. Using conventional colour coding I take it RED is to +ve and BLACK is to -ve?

 

Thank you.

 

IMGP3567.JPG

david1.jpg

Please don't connect it like this.   On the back of the meter the contacts are coloured red and black. Using conventional colour coding I take it RED is to +ve and BLACK is to -ve?

 

Big banG! It goes in series with the loads not wired across the battery!!!!!

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I wouldn't use it at all.  It would need extra cabling which would add to voltage drop, and most of the time would probably barely register the current.  If you want an ammeter, get a digital one with a separate shunt, and with higher capacity.

Use the hole for a temperature gauge which will be much more useful.

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18 hours ago, Johny London said:

One last thought - I like the idea of the remote shunt. You could do a shunt for each battery circuit and have a switch to choose which the ammeter was displaying. Most useful :)

But if you stick with the 60A full scale deflection, then when it monitors charge to the starter battery it will show close to bugger all, and if it's on the domestic bank in a circuit featuring he inverter, it will potentially need to measure more than the maximum 60 amps it is calibrated for.

It is not suitable for either use.

 

2 hours ago, dor said:

I wouldn't use it at all.  It would need extra cabling which would add to voltage drop, and most of the time would probably barely register the current.  If you want an ammeter, get a digital one with a separate shunt, and with higher capacity.

Use the hole for a temperature gauge which will be much more useful.

^^^^^
This

Edited by alan_fincher
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So, it's not really the ideal meter for either situation, due to its scale and rating and type. (A digital one will show 0.5 amps as clearly as 50 amps obviously). But on the other hand, the op likes it (presumably) and it would show that something is wrong if there was a fault condition, which would be useful.

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7 hours ago, Boater Sam said:

Please don't connect it like this.   On the back of the meter the contacts are coloured red and black. Using conventional colour coding I take it RED is to +ve and BLACK is to -ve?

 

Big banG! It goes in series with the loads not wired across the battery!!!!!

Thank you for the warning, I perhaps worded it badly as I know an ammeter should be wired in series.

With regard to the temperature gauge suggestion I already have one, thank you.

As I have already drilled the hole I will possibly just put the ammeter in the hole but not connect it to anything.

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32 minutes ago, Ray T said:

As I have already drilled the hole I will possibly just put the ammeter in the hole but not connect it to anything.

That makes sense. Nothing wrong with a dummy gauge if it looks aesthetically pleasing. 

 

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