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tverweij avatar image
tverweij asked

MPPT Max Charge current not using BVM Battery current

I have a BVM712 Smart, that is transmitting Battery Voltage and Current sense. And I have a Smart Solar MPPT 150/85 that is receiving Battery Voltage and Current. The are in the same VE.Smart network. Firmware of the BVM is 4.12 and the firmware of the MPPT is 1.61

I have set the Max Charge Current in the MPPT (settings menu: Battery) to 26 A to make sure my battery is charged at 1C (my battery bank is 260 Ah).

When I look what happens now, is that when I have a load of 10A, the battery wont charge higher than 16A. With a load of 20A, only 6 A is charged into the battery.

This means that this setting is limiting the charger output instead of the battery input as provided by the BVM712.

I think this is a bug in the MPPT firmware.

As the setting clearly says "Max CHARGE current", and the charge current is provided by the BVM - the current measured by the MPPT itself is the charge current + load, so it should use the BVM value instead.



bug reportcharge current limit
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
26A is only 0.1C for a 260Ah battery.

1C would be 260A

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snoobler answered ·

The MPPT is a charger, and it can work independently with no other devices connected, so this value is intended to set the maximum output of the MPPT. Since it's a charger, it's called "charge" current. You are extrapolating additional desired function. If this value didn't behave as you observe, there would be no way to limit total output from the MPPT.


You want features not available at this hardware level.


The function you seek is available with the addition of a GX device and the DVCC feature. The DVCC can manage ALL connected chargers to limit CHARGE current to what is specified in DVCC while allowing all sources to provide additional current as loads require.


For the above DVCC function to work, you would need to set the MPPT to 85A. If you left it at 26A, the MPPT would continue to limit output to 26A.





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tverweij avatar image tverweij commented ·

"If this value didn't behave as you observe, there would be no way to limit total output from the MPPT.

Why should you want to limit the output of the MPPT instead of the battery charge current (that is known)?

I can not think of a reason to want that,

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snoobler avatar image snoobler tverweij commented ·
MPPT can function with no other devices. Flooded Lead Acid batteries may not be able to handle the full array output, so one would need to restrict current via this setting.


Again, to get the function you want, you need a GX device and DVCC enabled.

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tverweij avatar image tverweij snoobler commented ·

Yes, it can function without any other devices.

And then it is completely logical what you are saying.

But with the information from the BVM is it completely wacko to go for the output instead of the BVM value.

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kevgermany avatar image
kevgermany answered ·

@tverweij

To be clear. The BMV cannot control the MPPT in your current installation. It simply reports what it measures.

So MPPT output is permanently limited to 26A by your settings. As you're seeing, current to the battery will always be MPPT output - loads.

As @snoobler said, you must add a GX device to gain the control you expect. This will control the MPPT and allow battery charging at 26A. But if there's insufficient solar, load will take priority.


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tverweij avatar image
tverweij answered ·

You both say that the BVM cannot control the MPPT and that may be true.

But the MPPT is already measuring the tail current using the BVM information and correcting its output accordingly. So, it is already taking the current measurements of the BVM in account at that stage - and that is why I think it is a bug that it is not taking it in account for the maximum charge current; it is clearly able to do that, it just won't as this is not programmed into it.

And as that is illogical, I call this a functional bug as a programmer.

Hoping for an answer of someone at Victron itself - not from resellers or hobbyists.


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snoobler avatar image snoobler commented ·
You may see it as a functional bug, but you're not acknowledging that you want a feature for which a solution already exists, yet you don't want to spend the money necessary to get it.


Not all options are available on all products.

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kevgermany avatar image kevgermany ♦♦ commented ·
No. The MPPT is not measuring tail current. This is controlled by the battery alone.


The MPPT simply works on voltage. NOT current.
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snoobler avatar image snoobler kevgermany ♦♦ commented ·

I think they're referring to this:


https://www.victronenergy.com/media/pg/VE.Smart_Networking/en/voltage,-temperature-and-current-sense---further-details.html


The MPPT uses the shunt current for tail current instead of the MPPT measured current.

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