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helimech avatar image
helimech asked

Solar System Issues

I just installed a 600W (6x100) solar system wired 3S2P on my RV. The controlled is a Victron SmartSolar MPPT 100/50. The controller is connected to my Cerbo GX via a VE.Direct cable and the “PV Charger” Box shows up on my GX Touch 50 in the lower right area. I also have a BMV-712 connected to the Cerbo GX via a VE.Direct cable and get a “DC Power” Box on the GX Touch 50 in the lower middle area. With the PV Cutoff/CB in the OFF position the GX Touch 50 shows 0W in the PV Charger box and -8W in the DC Power box. The battery shows 8W. When I turn the PV Cutoff/CB to ON the GX Touch 50 shows 570W in the PV Charger Box but now shows 781W in the DC Power box. The battery now shows a drain of -211W. Where is this 781W of DC Power coming from? Everything in the RV is turned off. Its only there when the Solar panels are on. Thanks for any help with this.

MPPT SmartSolar
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4 Answers
kevgermany avatar image
kevgermany answered ·

Sounds as if it's not cabled correctly.

Output negative of the MPPT should go to the load/system side of the shunt, not the battery or battery side of the shunt.

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helimech avatar image helimech commented ·
The positive and negative output of the my MPPT go to my Lynk DC Distributor.
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Duivert NL avatar image
Duivert NL answered ·

Can you show a vrm screenshot?

You said dc power box in lower middle, but it should be battery

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helimech avatar image helimech commented ·

solar-panels-on.jpg

Solar Panels ON


solar-panels-off.jpg

Solar Panels OFF

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solar-panels-on.jpg (7.7 MiB)
solar-panels-off.jpg (7.7 MiB)
helimech avatar image helimech commented ·

vrm-screenshot.png

Here is a VRM screensht this morning so solar output is low. As the solar output goes up so does the DC Power reading.

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vrm-screenshot.png (96.9 KiB)
Duivert NL avatar image
Duivert NL answered ·

Looks to me as your bmv is configured as DC measurement instead of battery measurment

Could that be the problem?

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helimech avatar image helimech commented ·
Do I check that in the BMV-712, the Cerbo GX or the GX Touch 50 settings?
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pwfarnell avatar image pwfarnell helimech commented ·
In the BMV712 settings.
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helimech avatar image helimech commented ·
Checked and its set to Battery Measurement
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helimech avatar image helimech commented ·
Just checked and it was set to Battery Measurement. Really confused now. If I have the solar system on and no DC stuff on the watts showing in the DC Power box on the Touch 50 are higher than the solar output. In this state the moving graphics of the Touch 50 shows flow from the battery to the DC Power. If I put the inverter on and a AC load the watts in the DC Power box go down and the flow reverses and goes from the DC Power to the batterys then to the inverter along with the solar output. How is the DC Power supplying power to the batterys??
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Duivert NL avatar image Duivert NL helimech commented ·
Do you have DC power? Or is there nothing connected?


then you should turn has DC off in vrm

Settings > system setup > has dc system

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pwfarnell avatar image pwfarnell helimech commented ·
The DC box is an internal.calculation. The Cerbo knows the current flow in/out of the battery, the inverter and the MPPT, therefore anything else must be either flowing into the DC loads or coming from a charger that is not measured, often an alternator. Therefore, in your first screenshot the solar is producing 570W, the battery is discharging 211W therefore the unaccounted power going into the DC system is 570 + 211 = 781W.


So we come back to the original premis that something is wired up wrong and the solar is not being counted by the BMV 712.

RVs can be problematic at times, especially with chassis ground. Do you have a connection from the leisure batteries to either the chassis or the starter battery. If you do, these connections must be made to the load/system side of the shunt NOT to the battery or the battery side of the shunt. The only connection to the battery negative is the shunt and the only connection to the battery side of the shunt is the battery. Ground connections ate the single most common cause of misreading shunts in RVs.

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helimech avatar image
helimech answered ·

Looks like this now! Might be good. Great idea to turn off the DC Power option. I thought I needed that because of the DC-DC charger. Still learning this system, not easy. Thanks very much for all your help and patients. Cheers

now.jpg


now.jpg (77.8 KiB)
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Duivert NL avatar image Duivert NL commented ·

Im not 100% sure, but i think has dc system is for an extra dc input rather than output, like charging from an alternator


Also its not an real accurate measurement

The 12/12/30 dc dc orion, has no communication with the system

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pwfarnell avatar image pwfarnell Duivert NL commented ·

The has DC system is for when you have DC loads or chargers that are not communicated by the charger.

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Duivert NL avatar image Duivert NL pwfarnell commented ·
Ok so he should turn has dc system on, or should he better use a shunt on th DC load for good measurement?
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pwfarnell avatar image pwfarnell Duivert NL commented ·
Has DC system does not affect the battery or solar current / power readings so there is no harm in having it on normally as long as you realise it is a calc. If you definitely have no loads or unmetered chargers then it should show close to zero but it will normally show some current as the system inefficiencies get put there. If it shows large discrepancies it normally means your battery shunt is not wired correctly or has another problem. Using a SmartShunt to meter your DC system as an energy meter is the best option because the values are then real.
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