question

snoobler avatar image
snoobler asked

Why is MPPT reporting nearly 3V higher than Pylontech and multimeter value?

Cerbo GX v2.89

MP 48/5000/70-100 v476

MPPT 250/100 VE.Can r2 v3.10

Pylontech batteries

DVCC forced on

SVS forced off

Pylontech is default battery monitor


Unable to charge above about 40% SoC


MPPT current starts throttling when MPPT reaches 52.4V while Pylontech/multimeter reports 49.6V. MPPT reports being under external control.


Why isn't MPPT being fed the Pylontech BMS voltage value?


This is not a new system. Uncertain of timing, but batteries were able to mostly charge to full pretty regularly, but not being able to attain more than 40% somewhat recently.


Originally there were four batteries. Two have generated faults and are being tested by the distributor. The remaining two do not indicate any faults.

1680373445817.png


Please note that this ~3V delta is present under charge AND discharge.


EDIT: I have enabled the MP battery monitor on the dashboard, and it reports within 0.1V of the Pylontech value.

MPPT Controllerscerbo gxPylontech
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9 Answers
snoobler avatar image
snoobler answered ·

I believe this addresses part of my issue:


https://community.victronenergy.com/questions/157885/big-voltage-difference-between-pylontech-bms-and-m.html


MPPT voltage out of calibration? How to resolve?

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snoobler avatar image
snoobler answered ·

Also want to confirm that the multimeter readings are taken AT the MPPT battery terminals. The VictronConnect reported value is almost 3V higher.

Multimeter measurement is consistent with BMS and MP battery monitor value (enabled only for additional data).



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klim8skeptic avatar image klim8skeptic ♦ commented ·
Tried using a VE Direct cable for coms between the GX and mppt rather than a rj45 cable?
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snoobler avatar image snoobler klim8skeptic ♦ commented ·

Don't have one, and one is at least 3 days away.


Going to try separating the MPPT from the system and having it operate independently to see if the voltage error is present.

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snoobler avatar image snoobler klim8skeptic ♦ commented ·

Completely disconnected the MPPT from VE.Can, disconnected PV, disconnected battery, reconnected battery, reconnected PV.

52.2V on VictronConnect, and 49.5V on the multimeter at the battery screws on the MPPT terminal.


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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @snoobler,

The first thing I would try is to update the MultiPlus to the latest firmware version, and VEConfigure to the latest, and then disable the vsense option. There was an issue that caused system voltage to drift and this may resolve it.

disable-vsense.jpg


disable-vsense.jpg (48.7 KiB)
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snoobler avatar image snoobler commented ·
Thank you for the recommendation. MP is on v476. I do not see the Disable VSense option, so I presume that was enabled at a later version. I have a Quattro in another system running v497, and it's still not an option.


I am always hesitant to update the firmware on VE.Bus devices unless absolutely necessary. Do you truly feel this is necessary when I have verified the MPPT reads 2.8V higher in VictronConnect than measured at the MPPT battery terminals when isolated from the GX and operating independently?


FWIW, I did update 250/100 to v3.13 from 3.10. No change.

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snoobler avatar image
snoobler answered ·

@Guy Stewart (Victron Community Manager)

I'll try it if you insist, but since there is no "system voltage" due to DVCC SVS forced off by Pylontech interface, I don't see how "system voltage" could drift as there is no "system voltage" and all devices operate based on their own measured voltage.

From what I see, there is nothing feeding the MPPT any voltage information.

BMS, Multiplus and voltmeter all agree. MPPT is 2.8V higher when connected via VE.Can AND when it's operating completely independently.

Thanks!

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Alexandra avatar image Alexandra ♦ commented ·

@snoobler

Does it happen without solar connected? Just connected to battery?

Pre rma bench test instructions.

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snoobler avatar image snoobler Alexandra ♦ commented ·
I don't recall. I'll check.
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snoobler avatar image snoobler Alexandra ♦ commented ·

MPPT reports:

1680629394903.png


MPPT battery terminals: 49.4V
VictronConnect: 52.2V
MPPT PV terminals: 0V (PV breaker disconnected)

GX also reports 49.4V


I can't do everything listed in the RMA instructions. I've isolated the MPPT from both the PV and the GX, and it's reporting voltage 2.8V high. There is no VE.smart SBS or other device installed.


I don't see how additional testing is necessary. This appears to be an independently operating MPPT reporting incorrect voltage. Since Pylontech is setting the voltage limit, but not feeding the MPPT the OCV, the MPPT starts tapering the current in "absorption" at a voltage 2.8v higher than the battery, thus preventing the battery from getting above 33% SoC. Yes. It's gotten worse since posting.


If @Guy Stewart (Victron Community Manager) insists, I'll update to v500 (or newer) and disable Vsense, but I don't see how this inverter setting could affect an MPPT that's independent of the GX network.



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snoobler avatar image
snoobler answered ·

UPDATE:

MPPT has be been completely disconnected from the Cerbo and BMS control reset within VC. Absorption has been set to 54.55V (3.64V/cell) with an intended target voltage of 51.75V (3.45V/cell). This reflects the measured +2.8V error reported by VC vs. direct measure at terminals.


3.64V is likely problematic due to likely imbalance issues from long term insufficient charging, but it's still technically a safe voltage, and the 3.45V should be sufficient to achieve full or near-full charge. The goal was to select a voltage that was safe to use if the MPPT went that high and would charge to a high SoC if the 2.8V error remained.


MPPT is still showing the +2.8V voltage error in VC at rest compared to its battery terminal voltage.


Again, GX, BMS, MP battery monitor and voltmeter all agree within normal instrument deviation and are about 2.8V below the VC reported MPPT battery voltage.


1680792062907.png


Decent charging this morning, and the batteries have achieved a state of charge higher than they've seen in months. Recent days with decent sun wouldn't get above 33%. It would go to absorption almost immediately and only trickle a few amps to the battery for the rest of the day. The MPPT would react to loads and supply additional power. A 3rd battery that was generating errors due to low charge states has been added back to the bank, its LED SoC meter is consistent with the other two, and it has not reported any faults.

So I see two options:

  1. GX, MP, BMS and voltmeter are all reading the wrong voltage, BMS is also reporting incorrect SoC, and three battery LED displays are also showing incorrect SoC.
  2. MPPT reporting the wrong voltage (bad/miscalibrated MPPT).

Thoughts?


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snoobler avatar image
snoobler answered ·

In reviewing the pre-RMA bench instructions @Alexandra linked, I found the following:

1680803210050.png


I believe the fact that I have three instruments in agreement (BMS, MP and voltmeter) while VC reports a voltage 5.6% (2.8V/50V) higher, I believe that I have demonstrated this unit is faulty. It is less than three years old and should be under warranty.

EDIT: want to reiterate that the unit is operating independently when this measurement is made. No connection to the Cerbo. No VE.Smart network present and no other VE.smart capable devices (no SBS, smartshunt, BMV-712, smart dongle, etc.) present.



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nickdb avatar image nickdb ♦♦ commented ·
Warranty is 5 years. So no worries there.
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snoobler avatar image
snoobler answered ·

And for the first time in nearly a year, 100% indicated:


1680909104562.png





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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hey @snoobler , you’ve spent more than enough time on that MPPT; I agree, its most likely broken.

I’d stop spending time on this and contact your dealer.


Apologies for the trouble it has given you!

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snoobler avatar image snoobler commented ·
Thanks! Conversation has already started.
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agroventuresperu avatar image agroventuresperu commented ·

Hi @mvader (Victron Energy),


I could not figure out how to send you a private message, so I will post my response here.

I am the owner of the MPPT in question. @snoobler, an engineer from the United States, has been helping my wife and I diagnose this problem. Our dealer was notified back in August shortly after the problem started. Here is a thread I created after I noticed the problem (now almost one year ago):

https://community.victronenergy.com/questions/139147/batteries-now-only-charge-to-88.html?childToView=150974#answer-150974

Can you please reach out to me in the next week or so to talk about finding a solution? We have already tried our dealer and the South American sales rep, and are not satisfied with the response.

(Redacted for privacy reasons: if said individual has any intention of contacting me privately, they can figure out how)

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agroventuresperu avatar image agroventuresperu commented ·
@mvader (Victron Energy)


This is getting ridiculous. To service our warranty with a replacement unit, the authorized dealer we bought the unit from in Peru, Novum, wants us to pay for someone to come out and install the new charge controller (as if we do not know how to operate a screw driver). We are a 20 hour drive from Lima. Guess who will have to cover those travel costs and "labor" costs?

The Victron Sales Rep, David Lopez, said we could pursue warranty service with any other authorized distributors in Peru. So we contacted another, Andre Calvo (Gerer L'Energie), who has now told us that if we want a new unit we will have to cover the importation fees. We already paid full retail price for our defective unit, so not sure why we would have to pay a dollar more for something that supposedly is under warranty.

The experience dealing with the distributors in Peru has been negative to say the least. I'm trying to figure out if the behavior from the distributors is their personal attempt to milk more money out of their customers or if Victron is trying to get the end-user to pay for warranty service?

We just want a new unit. We are willing to pay out of pocket and then be reimbursed for the retail cost after the distributor examines the currenty faulty unit. Can you please make it happen?

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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ agroventuresperu commented ·

Hi Scott, my apologies, I only see both of these messages now; had missed it in April.

I’ll check and get back to you.


Matthijs

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agroventuresperu avatar image
agroventuresperu answered ·
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