adding a voltmeter

[JPBeck]

Adding a voltmeter to my system to get more precise readings, the solar controller was not reading the same voltage at the battery.

[Cdash]

Was the controller reading higher than the batteries?

[JPBeck]

No lower-- For instance the controller would read 12.4 when the battery bank was at 12.6-- that's a big difference. Why do you ask?

[Mustang65]

Do you have the 2 meters wired directly to the battery(s)? Terminated at the same points? How do you have the batteries wired?

Don

[JPBeck]

Two meters? I have one dedicated meter, and the solar controller hooked up to (4) 6 volt batteries in a series (2 on the tongue and 2 under a dinette booth.







So basically I ran 4 wires down from the voltmeter along side the refrigerator down under the trailer, to the tongue, then installed all the ground wires to the shunt and a single wire to the positive battery terminal.

[Cdash]

Originally Posted by JPBeck

No lower-- For instance the controller would read 12.4 when the battery bank was at 12.6-- that's a big difference. Why do you ask?

I was wondering if you were getting voltage coming out of the controller and getting voltage loss to to the batteries. Controllers should be as close to batteries as possible, and if the wire wasn't large enough the voltage loss would leave the batteries less than what is coming out of the controller.

Your numbers don't seem to indicate that though....

[JPBeck]

Yeah thanks, I used 6 or 8 gauge when I ran the solar, and there's only about 15 feet of lead. I don't know why there's a difference, but apparently it's a common issue. This is my 3rd controller and the other two had similar voltage discrepancies.

I installed 22 panels on my home and ran into the same problem.

[JohnWedell]

Both meters may not be totally accurate.

[JPBeck]

Yeah, that's true, but the one I installed reads exactly as my hand held Fluke 115 True RMS Multimeter- so I'm confident.
Thanks

[Hivoltage98]

I have 2 of them also. One for solar power charge current input and one for true battery load output


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[JPBeck]

Nice-- does your controller display different then those?

[Hivoltage98]

Within a few volts. There could be voltage drop from the wire runs. These aren't precision instruments for nuclear reactors.


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[Mustang65]

Originally Posted by Hivoltage98

I have 2 of them also. One for solar power charge current input and one for true battery load output

Hivoltage98, I see you have enough room there for one more Digital Voltage Display meter. You need to monitor your 110VAC voltage and usage to make the system complete. I just purchased 2 (one for the house and one for the TT) See below. I tested the one on the house 220VAC (had to wire 2 CT's in series one for each leg) and it actually matched the electrical meter's flashing led (which I monitor). As ordered, it is for monitoring 110VAC, I modified for the 220VAC.
I have been using the smaller AC one..... never happy.

Don

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RVing with SOLAR

[Hivoltage98]

My 120v is monitored by my power management system. The meter is not installed yet. I have the progressive EMS system.


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[JPBeck]

So when you run two of these meters do you use the same shunt and just rearrange the wires on the other meter?

[Hivoltage98]

I have a shunt for each meter. Also it's always wise to fuse your battery banks in case of a problem.


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[Mustang65]

Originally Posted by Hivoltage98

I have a shunt for each meter. Also it's always wise to fuse your battery banks in case of a problem

OK, that brings us down to the mV ratings on the shunts. Are both shunts the same mV rating? Should be 50, 75, or 100mV. If you can, switch the wires from the meters to the shunts and see if the voltage discrepancy follows the shunt resistor. There is no harm in switching them. Don't forget they are all made in China where Quality Control in mfr is at the bottom of the list.

There is no voltage loss in the shunt to meter leads as there is no load, so the type cable used can be eliminated.

Let us know what the outcome is.

Glad you fused both battery banks, a lot of people overlook that safety feature.

Don

My Registry

RVing with SOLAR

[pconroy]

Originally Posted by JPBeck

Yeah, that's true, but the one I installed reads exactly as my hand held Fluke 115 True RMS Multimeter- so I'm confident.
Thanks

I was just going to ask if you had a trustyworthy source. Fluke counts.

[Hivoltage98]

Originally Posted by Mustang65

OK, that brings us down to the mV ratings on the shunts. Are both shunts the same mV rating? Should be 50, 75, or 100mV. If you can, switch the wires from the meters to the shunts and see if the voltage discrepancy follows the shunt resistor. There is no harm in switching them. Don't forget they are all made in China where Quality Control in mfr is at the bottom of the list.

There is no voltage loss in the shunt to meter leads as there is no load, so the type cable used can be eliminated.

Let us know what the outcome is.

Glad you fused both battery banks, a lot of people overlook that safety feature.

Don

My Registry

RVing with SOLAR

Yes but there is loss for the voltage portion of the meter.


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[hoppers4]

The difference could come down to the calibration of the devices and the shunt. The claimed accuracy of the Bayite meter is 1%. At 12VDC that comes out to a possible error of plus or minus .12VDC. The Solar Charger meter is also going to have a plus and minus tolerance of some value. The shunts are also going to have a calibration error. Throw all these errors in together and they could easily add up to .2VDC.

The Fluke is also going to have a calibration accuracy. It could be off in the same amount and direction as the meter you're comparing it to.