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PostPosted: May 14th, 2017, 1:27 pm 
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Location: Northern NJ
I've always been curious to know in realtime how many amps different loads were taking, from 12v lights and fans, to 120v microwave and a/c heating element.

But being lazy, I really didn't want to wire in any meter shunts (yet). Fortunately on eBay ($12-20) I found both AC and DC versions of volt/amp meters which use a loop sense instead. So all I had to do was disconnect a couple of wires, slide the amp sense loops on,and put the wires back. Then run some tiny wires for volts.

Unscrewing the distribution box and pulling it outward, allowed running the sense wires out and behind over to the meters location.

Since no shunts are needed, just tiny wires, my original plan was to run the wires up to the stove hood monitor and mount the meters in the lefthand blank side. But I was in a rush today and opted for closer to the power sources.

Below you can see the loops, one below the main AC breaker, and the other around the red DC fuse panel feed wire. To the left are the meters (DC top, AC bottom) mounted into a fiberboard temporarily held up slantwise with tape over an access hole I cut out.
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Above is reading 13.5 DC volts, and 121 AC volts with 0.5A being used by the converter/charger. (Turning on the roof a/c heater coil jumped that to 14A !)

And here buttoned up a bit better. Will fancy it up later. Note this on a '94, where the distribution panel is below the fridge, and in front of the generator box. DC usage here is also 0.5A (200mA for the gas sensor at lower left and 300mA for one roof LED lamp set -- a fan can jump that to 4A).
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That top DC meter alternates between volts and amps, but I'm replacing it with another $12 loop meter that has both volt & amp displays like the bottom AC meter.

Next up: installing a remote shunt meter at my single house battery, which either wired or wirelessly transmits info on battery power in/output to a remote head display unit. The price for this technology is astonishingly low:
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The left box is the shunt and meter electronics, with optional wireless transmission to the remote display head on the right (which only measures about 1.5 x 2.5").

It's sort of like a trimetric monitor for cheap. I will let everyone know if it works well.

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Last edited by kdarling on July 17th, 2017, 10:45 pm, edited 8 times in total.

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PostPosted: May 29th, 2017, 7:44 am 
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Okay, so the two piece remote meter (see end of post above) I got off eBay came in from China. Took about 8 days to ship to NJ, pretty normal.

The meter will be able to sum up and display all the charging and discharging of the house battery.

The plan was to put the reader/shunt part next to the house battery (in my '94, that is just one battery under the passenger side of the engine hood), and use its wireless mode to talk to the display head placed somewhere in the main cabin. (If all the metal got in the way, then I'd run a USB cable instead.)

Like most such meters, the shunt has to go on the negative side of the load, so that meant in my case that I had to go under the hood, and connect between the chassis ground (the return side of the house load) and the battery negative post. You guys with the later rear batteries should have it easier.

So I went to an auto parts store and got a short battery cable (a ground strap would also do). A small red wire gave it positive power for the electronics. A small 2x2x4" plastic container to keep it dry came from the grocery. Still figuring out placement, but here's my test setup (the battery negative cable used to connect directly to that fender screw):
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First I plugged the display unit directly into the sender to make sure it was reading and that they were both set to the same wireless channel.

Then I took the remote display head inside the cabin, using a 12v outlet & USB adapter to power it. To my pleasure, it could read the sender from under the hood, back almost as far as the sink. I'll probably mount it closer though, in the overcab storage wall next to the old VCR slot.

Here's a blurry shot with shore power turned on, charging the battery. I had gone inside to watch TV, and so after about one hour and fifty-four minutes (1:54), the converter/charger had given the battery almost 9 amp hours of juice:
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My Progressive Dynamics charger puts out 13.6v from its location back near the fridge area, so I apparently lose .02v on the way forward. Hmm. Seems too little. Will need to check with another meter.

Now a couple of minutes later with the shore power turned off, running the Fantastic fan from the house battery. The accumulated AH and WH will start to tick down now that the battery is being discharged:
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The values update once a second, so you have a constant running total of the amp and watt hours that have gone in or out of the battery.

I'll have to get used to positive numbers and green == discharge, with negative and red meaning charge, but hey, for $25 I can do that :)

You can set the amp hour rating of the battery and other parameters, so I just need to get it fully charged and then set that as the full 60AH point in my case. You can even hook up a relay for it to disconnect the battery load if it falls below a custom voltage (LVD).

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Last edited by kdarling on May 29th, 2017, 12:45 pm, edited 1 time in total.

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PostPosted: May 29th, 2017, 10:37 am 
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Location: 1999 Concourse
Isn't information great?

A couple of notes for an amp counter type meter:

1) Maybe this is one of the other parameters, but there is typically a Peukert factor you can set (factor published by battery mfgr.). Lifeline's factor is 1.125, but I think that's fairly low as batteries go.

2) One way people sometimes get tripped up by these (not saying you would) is that they set the battery capacity for the published amp hour rating (say 60 amp hours in your case), but then don't readjust as the battery loses capacity over its lifetime. If you don't do a true load test, you can just estimate. That's what I do, adjusting down each year by about 20% (I'd rather be conservative than not).

3) In case people follow in your footsteps, I presume the red cable coming out of the right side of the shunt is a negative cable (typically black or yellow), and is the same one that loops over to the chassis on the left. Just so no-one thinks a positive cable should attach to the shunt or the chassis :o .

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PostPosted: May 29th, 2017, 11:17 am 
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PS: Looking at the photo again I have a question: How are the two cables that connect to the shunt making good contact through the plastic? Maybe it's cut away but from the photo I can't tell. I know they are touching the stud, but typically there is a metal boss of some sort at the base and that's where the lug makes good contact.

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PostPosted: May 29th, 2017, 12:41 pm 
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Ha, you're correct on all points, as usual.

Even down to the fact that later I realized it was only making contact with the edges of the center posts and needed to actually be directly on the shunt, which is leadng to rethinking the enclosure!

Btw, I also put a spare loop sense volt/ammeter on the solar panel output. (Heck, for as low as $10 for these things, you can practically instrument every individual circuit if you wished :lol: )

Anyway, I'm getting a much better feel now for how it all actually operates in reality vs theory, as each piece of the system does its thing at different times.

And yeah too bad they didn't have a black cable at the store. Maybe I should paint it.

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PostPosted: May 29th, 2017, 8:56 pm 
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It really is neat once you can see it all happening. As you say, it becomes much more understandable. Maybe I'm slow, but it wasn't until I had watched my solar controller/meter(s) for awhile that I started to tune into the nuances. I had the basic idea before that, but still.

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PostPosted: June 10th, 2017, 4:03 pm 
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So, I got in a dual display DC volt / loop ammeter, to replace the green meter that constantly cycled between volts and amps.
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Installation of the loop was again easy... just unscrew the incoming 12v wire and slip the sensing loop over the end, then rescrew the wire.

Since it only comes with about a three inch sense loop connector, I cobbled up an extension using the long three wire cable that the previous meter came with.

I like the dual display but I think it might read slightly low on the volts. I'm going to have to do some testing and check if it has an adjustment.
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(The top DC and bottom AC meters are still in a temporary mount next to the circuit breaker box.)

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