mtucker502 avatar image
mtucker502 asked

MPPT won't charge while under external con

I have two Quattro 10kva 120v in split-phase using ESS.

I connected an EG4 Communications Hub (appears as a Pylontech Battery) so that my Cerbo GX could get a more accurate SoC reading of the EG4 LifePO4 batteries. After a few minutes the MPPT controller stopped charging the batteries. I then disconnected the EG4 Communications Hub, removed disconnected devices and restored the MPPT to non BMS control. However, the MPPT will not charge the batteries at all.

If I disconnect the VE.Can cable from the MPPT it drops into standalone mode and charges as expected:


If I reconnect the VE.Can cable it changes to external control and stops charging:


Here are the settings on my Cerbo GX:





Here are the Quattro's settings:




Note: For some reason Phase L2 doesn't show the full ESS settings. It's missing the Cutoff voltages (all set to 47V).

For some reason I have a low battery voltage alarm coming from the Quattro.


My questions are:

1) Why does the Quattro report a LV alarm when the voltage is 52.54?

2) My assumption is ESS is in external control of the MPPT. If this is correct, why won't it allow the MPPT to charge?

battery chargingESSMPPT SmartSolarsmart solar charging behaviourquattro 10kva
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2 Answers
mtucker502 avatar image
mtucker502 answered ·

I discovered that the Quattros will remain in pass-thru and the VRM portal will show them as still externally controlled even if the can-BMS device has been removed.

In order to fully recover from the EG4 Communications Hub (and I'd assume any other can-BMS you must go to Settings > Quattro > Advanced > System reset. This will reboot the Quattros and allow the MPPT to begin charging again.

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Alexandra avatar image
Alexandra answered ·


Every time you connect or disconnect the BMS comms you need to re boot the system. And reprogram for no bms control as you did.

You have in your basic troubleshooting shown it it the battery hub that is causing the problem.

I will start with the usual, is all the firmware on eveything up to date?

The low vattery warning is probably happening as the battery is disconnecting from the system (or opening contactors to prevent discharge) alternatively your ESS settings (dynamic cut off) are triggering that.

In the VRM advanced tab load up widgets for the battery CVL and DVL you will see what it us telling the system to do there. There is a chance the CCL from the comms is telling the system not to produce.

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mtucker502 avatar image mtucker502 commented ·

@Alexandra Thank you for helping out. I'm not sure which values are CVL and DVL. Is it the System Battery Voltage:



Here are the widgets I have:


When I disconnect the BMS from the canbus I do not disconnect the battery; it is always connected. In the graph above, I don't see where the battery voltage dropped below any of the defined values I have configured.

Which setting in VEConfigure, ESS or the Cerbo controls the low voltage alarm?

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Alexandra avatar image Alexandra ♦ mtucker502 commented ·


The system will not always shut down especially if there is solar or AC in, it will keep running. But it will notice a loss of battery reference hwnce the low voltage warnings.

If your battery is connected to the system, you should get the battery monitor widgets and that will have more information for the battery like cell on and max values as well as CVL and DVL.

High DC ripple warnings (which you have) are a sign of something happening on the DC side. Usually battery will be off or switching, if the wiring etc is all correctly dimensioned and ok.

The low voltage alarm will possibly be triggered by ESS assistant, and there is a setting on the inverter parr that also can affect it.

But the cause of the issue 8 times out of 10 will be the batteries disconnecting the contactor internally or bms shutting down. The other 2 out of 10 is DC breakers or disconnects that are used between the battery and the system giving grief.

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