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Old 02-12-2018, 10:50 AM   #1
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12V system performance monitoring

When I bought my solar panels and MPPT controller I also opted to buy the remote display unit in order to track the panels performance. After I got it all up and running, I discovered to my dismay that the display, despite having several different displays including system voltage, it does not display current out of the house batteries, (no external shunt) It does show current provided by the panels, and system voltage too, so I have some idea what’s going on. Still, I wanted to be able to see the current draw out of the batteries so I can see how different systems draw down the available amp hours. So, going on line, I found a small display unit that included a shunt that goes in the negative battery cable. I got it all installed yesterday, and bingo, I now can see the amps flowing out of the battery, but it turns out it won’t read charging current (amps in). So, if I turn on a 10A load, the new display may show zero amps while the solar panels are supplying the entire load. If its dark out, I can see the entire 10 amp load on the meter, but if I supply some charging current by starting the engine or plugging into shore power, the display goes to zero. So, it seems I have a twofold issue here. First is the fact that the solar, alternator and shore power inputs will supply loads without going through the house batteries. Second is that my new meter is one way only, current out. I haven’t fully figured out how to solve the first issue, but if I could at least find an amp meter that reads both ways, I’ll be able to gauge battery usage. So, my question is, does anyone know of an inexpensive amp meter that uses a 100A shunt (already wired and installed) that will read current into and out of the house batteries? I have a similar monitor I installed on my boat that does just that in addition to tracking amp hours up and down, and a lot more, but it was several hundred dollars and provides information I don’t need in the van. The two photos were taken at the same time and show current out of the panel supplying the stereo, but the new meter is showing zero current out of the batteries. Anyway, meanwhile, I’ll try to wrap my head around how to gauge total system performance, rather than just what’s coming into and out of the house batteries, but I'd love to find an display that reads current in both directions and uses the 100a shunt already installed………….
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Old 02-12-2018, 06:29 PM   #2
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The first problem is reality, power will get used from the charging sources first, anything left over will go to the battery.

For the second problem, the easiest thing to do would be to by another meter of the same kind, flipping the wires and you would read the other direction.


You could probably wire in a DPDT switch that would allow you to use one meter you would need to switch direction.

I find a 100 amp shunt to be limiting, don't you have a large inverter?

-greg
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Old 02-12-2018, 11:50 PM   #3
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Quote:
Originally Posted by Scalf77 View Post
For the second problem, the easiest thing to do would be to by another meter of the same kind, flipping the wires and you would read the other direction. You could probably wire in a DPDT switch that would allow you to use one meter you would need to switch direction.

I find a 100 amp shunt to be limiting, don't you have a large inverter?
-greg

I considered adding a switch, but hadn't thought of a second meter. Darn it though, real estate is tight already so adding another meter won't be my first choice. I really want to find a different meter that does both, using the currenly installed shunt, but for now I might just add a switch. As for the 100A limit, my inverter is only 400W and my other loads are only lights, a pump and the heater fan so I should be ok. I'd love to be able to charge at over 100A, but I don't see that happening any time soon.
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Old 02-13-2018, 07:47 AM   #4
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I've installed one of these and love it. With the BlueTooth option too.

https://www.amazon.com/s/?ie=UTF8&ke...l_87luiykapy_e

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Old 02-13-2018, 10:35 AM   #5
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I've installed one of these and love it. With the BlueTooth option too.Steve W Southern California
Thanks Steve. I have a similar Xantrex monitor on my boat, and yes it does provide a lot of useful information. The only downside to putting one in the van is the cost, although the Victron unit you referenced is about half what I paid for the Xantrex. I was hoping that a $14 meter would give me the info I want, but I guess the joke is on me for not doing more research first, but I didn't see any mention of one way current measuring in the specs. Let the buyer beware I guess, but not a huge loss. All I really want is to monitor volts and amps, so I'm hoping someone knows of an inexpensive meter that just does that.
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