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Old 03-06-2012, 08:50 AM   #1
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making a shunt?

I tossed out my old Univolt and need to possibly make a shunt to make the holding tanks read. Does any one know how to make one or where I can purchase one?
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Old 03-06-2012, 09:02 AM   #2
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Originally Posted by batt View Post
I tossed out my old Univolt and need to possibly make a shunt to make the holding tanks read. Does any one know how to make one or where I can purchase one?
A "shunt" is a wire that is placed across the 2 terminals of an ampere meter.

How much, and what size, depends on what you want the meter to read, as well as what exact meter.

Not something you can usually guess at, to be exact.

Andy
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Old 03-06-2012, 09:39 AM   #3
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A shunt has nothing to do with the holding tank reading.

You can get very high quality shunts for remote amp readouts at solar supply places.
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Old 03-06-2012, 03:34 PM   #4
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shunt

Thanks for the info
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Old 03-06-2012, 04:50 PM   #5
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from wikipedia:
In electronics, a shunt is a device which allows electric current to pass around another point in the circuit.
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Old 03-06-2012, 05:52 PM   #6
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A Shunt is a very precise voltage dividing device. Even though an ammeter reads out in amps. It is actually a millivolt meter that measure the voltage drop across the shunt. The shunt is also matched with the ammeter. They are a pair. The shunt is has a relatively low resistance but is capable of carrying high current values. Many shunts look like a copper bar others look somewhat different.
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Old 03-07-2012, 09:14 AM   #7
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I now know what that copper bar was on the Univolt!
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Old 03-07-2012, 09:48 AM   #8
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To shunt or not to shunt that is the question?

If I can read between the lines here....

Are you asking how to make the gauges work after the Univolt has been removed? If a new converter was installed all the 12 volt DC items in the system should work just as they did with the old converter. Without a converter none of the 12 volt items will function and you cannot "shunt" 120 volt AC directly to the 12 volt DC system without burning it up! "Danger Will Robinson that is not Dr. Smith!" You could however run direct wires off the battery to power just the gauges but I would not recommend doing that as a permanent fix. I have done this from a battery to test individual 12 volt items tho' so I suppose you could call that a shunt. Ed

p.s. I believe the copper bar was a shorting device to prevent electrocution when removing the safety cover from the Univolt!
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Old 03-07-2012, 08:44 PM   #9
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With respect to BigEd52. A shunt is not a safety device nor is it a device used on the 120 volt AC side of an electrical system.
In the photo above note the copper colored bar in the lower left hand corner of the fuse block. This is what a shunt looks like. The shunt is wired in series with the 12 Volt DC circuit. Note the black wire on the upper left corner of the shunt and what looks like a rivet on the upper right hand corner of the shunt just above the small red wire. The rivet looking device connects the larger white wire to the shunt itself. The two smaller wires connected to the shunt go to the ammeter. The slot that the small black wire on the shunt is connected is a means of calibrating the ammeter. By enlarging the picture you can see that the shunt is labeled for the ammeter as well as the battery and load connections.The black wire is labeled Trailer Battery Black and the white wire is labeled Load White. The ammeter in this case only reads the load on the trailer battery.
Without the shunt you will not get the ammeter to function. If you wire the ammeter into the 12 volt circuit without the shunt, you will blow up the ammeter.
In regards to the other meters and level guages, if they were wired to the full 12 volt system they can be wired that way again. If there is an internal voltage regulator on the guages. Which is common practice in the auto industry for instrument panel guages. You will need to connect the panel in the same manner as it was on the old converter.


Hope this helps.
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Old 03-08-2012, 09:32 PM   #10
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[QUOTE=TG Twinkie;1116836]

enlarging the picture you can see that the shunt is labeled for the ammeter as well as the battery and load connections.The black wire is labeled Trailer Battery Black and the white wire is labeled Load White. The ammeter in this case only reads the load on the trailer battery.

OK so basically the black , red and gray wires are useless, without the shunt. Who makes a ammeter which I can wire into the batteries to have a digital display of the batteries?

"white wire is labeled Load White"
Should this white wire now be run to the ground bar?

In regards to the other meters and level gauges, if they were wired to the full 12 volt system they can be wired that way again. If there is an internal voltage regulator on the gauges. Which is common practice in the auto industry for instrument panel gauges. You will need to connect the panel in the same manner as it was on the old converter.

There were only 5 other 12v circuits one # 5 is the car battery and circuit, and I guess one of those circuits carries the holding tank gauges.?

I find it interesting how different peoples interpretations of a given electrical problem can be!

If you would elaborate on the above it would be appreciated. Thanks, Barry
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Old 03-08-2012, 10:34 PM   #11
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If you're replacing gages, shunt, etc. I can whole-heartedly recommend a TriMetric Battery Monitor. It not only measures voltage (one or two batteries) and current, it also integrates the current with respect to time to generate a very accurate estimate of the amount of charge currently in the battery. I find this very handy when boondocking.

Easy to install, easy to setup and easy to use. I have the 2025RV.

- Bart
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Old 03-08-2012, 11:10 PM   #12
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If there were no shunt in the system in the photo the black wire would have to be connected to the white wire to complete the battery circuit.
Again the shunt is wired in series between the battery and the load, the load being the fuse block.
The shunt creates a very slight voltage drop that is read by the ammeter. The ammeter reads out in amps but is actually reading millivolts.
I would recommend Bart's solution to your situation if you feel you need a battery monitoring system.
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Old 03-08-2012, 11:43 PM   #13
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In taking a second look at the photo the shunt is wired into the negative or common/ ground side of the circuit.
I know this will sound confusing, so bear with me. The red and black wires coming from the trailer battery are the positive and negative wires respectively. The black wire is the battery negative and the white wire on the other side of the shunt is the trailer negative or common/ground. The white wire does not go to the fuse block only to the shunt. So again if there is no shunt the black and white wires should be connected together. The photo below should help clear things up, don't confuse the fuse in the negative/common with the fuse for the power on light in the photo. The negative side fuse is also a 50 amp.
.
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Old 03-09-2012, 03:50 AM   #14
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See how to make a shunt from 12" of #10 copper wire. Cost -- $2.08.

Zep
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