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How To Guide: Installing an Ammeter & Shunt


stuart

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How To Guide: Installing An Ammeter & Shunt

 

Introduction

This is a guide to installing a simple cheap Ammeter as can be found on ebay sites. The guide is likely to be similar for any brand ammeter.

 

Disclaimer

This guide is intended to demonstrate how I installed the unit, following the instructions manual and suggestions by fellow forum members. It is not intended as a best practise guide or to demonstrate my electronic ability. If you intend to install a similar unit on your boat, it is your responsibility to understand your boat electrics, your electrical capability and your ability to understand and follow the instructions.

 

If you damage the unit, your boat, its components or yourself, don't blame me! No liability is intended or implied.

 

Ammeter

The Ammeter was purchased from

 

http://stores.ebay.co.uk/new2006power-Digi...sQ3amesstQQtZkm

 

You will need the meter and a shunt like these.

 

Shunt

 

Ammeter

 

 

Generally the complete unit can be installed for about £25.

 

Ensure that 100A is enough to cope with your power requirements especially if you have a large inverter.

 

Things You Will Need Before You Begin

Inside the box

There are 3 items you will need:

  • The ammeter unit
  • A small 4 way cable and plug.
  • Shunt

Step 1 – Identify cables

 

The shunt MUST be installed in the negative cable connecting the domestic battery bank to your electrical circuits. To locate this just follow the negative lead from the battery to the circuits/fusebox inside the boat. Its possible that you have 2 negatives leads connected, one to the boats supply and one that runs to the alternator on the engine (or a split charge relay etc.)

 

If you want to measure both the current used by the boats electrical systems and the charge current supplied by the alternator you need to move all the negative connections that are currently on the battery to one side of the shunt (connecting to the large bolt holes).

 

On the other side of the shunt, you place a sufficiently thick cable which returns back to the battery negative terminal.

 

Important note: You must be able to provide high quality crimp connections on very thick cables – this needs a special tool. Ask on the forum if someone can help or check with your local chandlers.

 

Technically you can install this shunt in the positive cables however I have tried this and the ammeter gave incorrect readings and caused problems with other circuits – I don't advise it!

 

Step 2 – Installing the shunt

The supplied shunt does not have a mounting bracket or electrical isolation so it needs mounting in a location where there wont be a risk of other cables shorting against it.

 

To do this, I used a small plastic box (from Maplins) and a piece of wood cut to the internal size of the box. I drilled 2 holes in the wood at the same distance as the shunts bolts and pushed the shunt bolts into the wood to hold it securely. This also stops the shunt moving if the connection cables are pulled.

 

To fit the box/wood/shunt to the bulk head I simply drilled and screwed through both the wood and plastic box and screwed into place.

 

You will also need to cut out holes in the box to allow the cables to enter.

 

Step 3 – Connecting cables to the shunt

You may wish to cut the negative cables to make installation easier. I did this approach and then got crimp connections added.

 

On the left of the picture is the main battery negative cable which goes straight from the battery to the shunt.

 

The right side of the picture shows the main negative cable running to the inverter and electrical circuits, and the lower black cable running to the alternator negative.

 

Ensure the bolts are tight (I used some thread lock glue as well) and then assemble the shunt inside the box – ensuring that the cables are not pulled at awkward angles and there is no tension on them. Cable tie/clamp them into place so they wont get pulled out.

 

Attach a ring crimp terminal to some 1mm2 wire and connect this to left hand screw terminal (again I used some thread lock glue). Repeat this for the right hand screw terminal. These will be called the sensor wires.

 

Run these two cables back to where you want to site the ammeter. Make sure the cables don't chaff again steelwork – run them inside some conduit or spiral cable wrap.

ammeter1_html_2a8e6ae0.jpg

 

 

Step 4 – Installing the Ammeter

 

ammeter1_html_1d6e5be4.gif

 

The Ammeter is designed for panel mounting and needs a hole to be cut. The sizes are supplied with the Ammeter but as a guide a copy is below.

 

You will need to ensure that the hole is a tight fit or the meter will fall out. I used a small drill bit and a jigsaw blade to cut a hole in 9mm plywood.

 

Step 5 – Electrical Installation To The Ammeter

 

ammeter1_html_2d7c3894.jpg

Don't let the diagram above confuse you – its straight forward enough!

 

The biggest problem you will have is connecting cables to the very thin plug connector supplied with the ammeter. I found it easiest to strip a large amount of insulation off each cable and then wrap this around the connecting cable, using solder iron to join the wires. Use heat-shrink tube (put on cable first!) to cover and seal the joint.

 

  1. Hold your ammeter so it is the same as shown in the diagram above.
  2. Plug in the white connector to the socket at the top right.
  3. The top most cable (probably red) needs connecting to the boats +12v supply. Use a supply that is after the main isolation switch otherwise you will never be able to switch the meter off!
  4. The next cable down (probably black) needs connecting to the boats negative supply.
  5. The next 2 cables need joining to the 2 shunt sensor wires, one to each cable.

I'd suggest that a small fuse is placed in-line with the +12v supply to the meter. No more than 0.5A (500 milliamps).

 

I also cable wrapped the 4 connecting wires together at the end to prevent the small cables getting pulled out of the socket. Ideally secure to a fixed location or cable clipped to a bulkhead.

 

Insert the meter into the panel cut out, take care not to trap any wires.

 

Step 6 – Testing

  1. Double check your wiring is okay and nothing is loose.
  2. Switch on your boats 12v isolation switch
  3. The meter should flash and then light up
  4. Without the engine running, switch on a few lights.
  5. The display should show a minus reading (eg. -4.5) if it shows a positive reading, switch the power off and swap the 2 sensor wires over inside the shunt & test again.
  6. If all is okay, test a large load (inverter or fridge for example) and ensure the ammeter shows a negative reading.
  7. Switch off the large load.
  8. Start your engine, you should see a high positive reading – this is the charge being put into your battery's from the alternator.
  9. Stop the engine!
  10. Put the cover onto the plastic box to cover the shunt.

ammeter1_html_m7433aed2.jpg

Your finished!

:)

A PDF version of this document is available from

http://www.waterexplorer.co.uk/hosted/Deta...r-and-Shunt.pdf

Edited by stuart
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Another great guide, thanks Stuart.

 

I was going to use separate shunts to measure the charge and load,

but I do quite like the minus reading you are getting on battery drain. so I might just copy you!

 

 

Odd that it only works on the negative cable, i guess the negs are common in the meter and you'd need a separate supply to meter a positive cable?

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A brilliant guide Stuart.

 

Even a non leccy person like me can understand your guide and I'm sure I could fit one.

 

So the ammeter will tell me what power the alternator is putting into the battery , does that also include via the alternator controller a Sterling DAR?. The ammeter will also show me what power I'm consuming; all very useful info.

 

Is there another meter I can install which will tell me, at any time, how much available power I have in the batteries? To me it's like how much diesel I have in the tank before I run out. Sorry if it's a stupid question :)

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Is there another meter I can install which will tell me, at any time, how much available power I have in the batteries?
See the SmartGauge posts
does that also include via the alternator controller a Sterling DAR?
Yes, any input/output to the batterys.
Odd that it only works on the negative cable
I think this is a feature of this particular ammeter - more expensive units are perhaps better built!
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Obviously the MODS have run out of drawing pins, this is the sort of post that should be pinned!

 

 

The only problem with it is that it demands an insulated negative terminal on the alternator. Ones that are case negative or have a negative terminal that is connected to the case will almost certainly use the starter negative lead for at least some of the return current.

 

I think the meter manufacturers should do a touch of redesign so they can be fitted into either the positive or negative leads because it is not unknown for car alternators to be fitted to at least inland boats and some of the alternators I have seen with negative terminals have them connected to the case. \i am not sure how ordinary boaters are supposed to find out before they buy the meter and shunt.

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Why do you claim it can only be fitted to the -ve?

 

We've got a shunt based ampmeter, all be it with a diy shunt and a analogy millivolt meter, which mesures the current in and out of the domestic batterys. However ours is wired into the postive cable. Just by the isolator/change over switch.

 

 

Daniel

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Why do you claim it can only be fitted to the -ve?

 

We've got a shunt based ampmeter, all be it with a diy shunt and a analogy millivolt meter, which mesures the current in and out of the domestic batterys. However ours is wired into the postive cable. Just by the isolator/change over switch.

Daniel

 

The implication is (from a couple of posts, including the OP) that this particular device doesn't work properly in the +ve line.

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Why do you claim it can only be fitted to the -ve?

 

We've got a shunt based ampmeter, all be it with a diy shunt and a analogy millivolt meter, which mesures the current in and out of the domestic batterys. However ours is wired into the postive cable. Just by the isolator/change over switch.

Daniel

 

Yes, so is mine, but the picture is clearly labelled Alternator Negative.

 

I think it is to do with the "polarity" of the digital module relative to the supply.

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Yes, so is mine, but the picture is clearly labelled Alternator Negative.

 

I think it is to do with the "polarity" of the digital module relative to the supply.

 

I suspect you're right Tony. I notice on the diagram of the unit, somewhere above, that there is a dip switch marked "common ground". It's possible that switching this could connect the +ve to ground if wired into the +ve lead.

 

Chris

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  • 1 month later...
Ensure that 100A is enough to cope with your power requirements especially if you have a large inverter.

 

I'm going to fit a volt meter and ammeter, the guide above is brill and understandable, but what size shunt/meter should I use for our particular application.

 

9 x 110amp batteries 990 amps

Supplying

 

12 volt panel, regular 12 volt equipment, but all L.E.D lights.

 

3 Kva inverter, no regular heavy loads. regularily a 240 volt A+ rated fridge.

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I'm going to fit a volt meter and ammeter, the guide above is brill and understandable, but what size shunt/meter should I use for our particular application.

 

9 x 110amp batteries 990 amps

Supplying

 

12 volt panel, regular 12 volt equipment, but all L.E.D lights.

 

3 Kva inverter, no regular heavy loads. regularily a 240 volt A+ rated fridge.

e

Just thought I would refresh the question above, any assistance appreciated :P

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e

Just thought I would refresh the question above, any assistance appreciated :o

 

The voltmeter should read to at least 20 volts so it is not damaged by a charging fault.

 

The ammeter needs to be specified for the maximum current t it will be expected to read plus a small safety margin. What that will be depends upon where abouts in the circuits you install it.

 

If you insist on measuring the inverter current the it must be capable of indicating about 350 amps, but that might well affect the resolution at low currents. If you just measure the alternator output then specify a little over maximum. Exactly what you measure will also depends upon the location of the shunt - in the + or - side of the circuit.

 

Once you have specified the ammeter rating simply buy the matching shunt from the supplier. I am sure you could get better prices, but getting them as a pair is probably the easiest.

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The voltmeter should read to at least 20 volts so it is not damaged by a charging fault.

 

The ammeter needs to be specified for the maximum current t it will be expected to read plus a small safety margin. What that will be depends upon where abouts in the circuits you install it.

 

If you insist on measuring the inverter current the it must be capable of indicating about 350 amps, but that might well affect the resolution at low currents. If you just measure the alternator output then specify a little over maximum. Exactly what you measure will also depends upon the location of the shunt - in the + or - side of the circuit.

 

Once you have specified the ammeter rating simply buy the matching shunt from the supplier. I am sure you could get better prices, but getting them as a pair is probably the easiest.

 

Hi Tony thanks very much for that. Initially we'll fit one before the main battery bank isolation switch which will record the amps from the battery bank and also the amps when charging from the alternators when engine is running. (I think LOL) Not really bothered about the inverter side, the cable is so thick. I'm hoping I can fit a switch in line to the digital readout so to switch off when not on the boat. I think 150amp to 200 amps would be ample as the 12 volt system along with the inverter use would never reach that. The 2 alternators are rated at 50a and 90a although I appreciate they'll not put out their stated output.

 

There are digital meters and different rated shunts on e-bay at very reasonable prices from China, so I'll give them a go.

http://cgi.ebay.co.uk/3-1-2-Blue-LED-Digit...Q2em118Q2el1247

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