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Akshay Tanna avatar image
Akshay Tanna asked

Victron SmartSolar MPPT 250/85 Malfunction after power cut and BMS shut-off

I have a SmartSolar MPPT 250/85 connected to a a 48V/5000/70A multiplus II and a lithium battery. I have 8 PV panels - 50 V each (2 strings of 4 each) connected to the smart solar.

This is the second MPPT where I have faced this issue

When I have a power cut in the afternoon when there is a strong sun and good PV generation, the BMS cuts off the battery and the system shuts down. I then get a spark and smoke from the SmartSolar. after this, there is 0 voltage across my PV system when it is connected to the SmartSolar. If I disconnect the SmartSolar from the PV system, I have full voltage (170V) across the panels again.

MPPT SmartSolar
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4 Answers
nickdb avatar image
nickdb answered ·

What is your battery setup?

Any photos of your installation?

This really sounds like an installation/ battery issue.

A charger that suddenly has its load/battery removed is going to experience a surge as there is a lot of power that now has nowhere to go.

Correctly installed chargers just don’t behave like you’re describing ,I would suggest you get a professional to help you and check your installation.

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Akshay Tanna avatar image
Akshay Tanna answered ·

I have disconnected the charger now to send to the supplier. However the system otherwise has worked for over a year with no issues. But the cabling size and quality was appropriate for the set up.


The battery is a generic 48 V lithium battery. It was not very good - definitely was low quality(we bought it when there were many power cuts across the country, and had very few options). We were currently looking to change the battery anyways.


Is there a way to configure the remote on-off to shut down the charger when the bms shuts down the battery?



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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

The MPPT needs to be shut-down before the BMS cuts-off the connection to the battery.

Maybe it's enough if you reduce the charging voltage of the MPPT.

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Akshay Tanna avatar image
Akshay Tanna answered ·

Thanks @nickdb and @Matthias Lange - DE

Matthias, you have mentioned you have dealt with this issue a few times in https://community.victronenergy.com/questions/28201/controller-damage-if-the-battery-is-disconnected-b.html


Did you find a viable solution for this?


I see that you suggest reducing the charging voltage, does that mean reducing the voltage from the PV string, I dont see how the charging voltage can be reduced?

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nickdb avatar image nickdb ♦♦ commented ·

Best thing you can do is get a battery that is the right spec and reliable and which talks to the GX so charge can be managed. Ultimately that is your issue, anything else is just wasting money on a bandaid.

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Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @Akshay Tanna

You need something to absorb, for a short period of time, the voltage/current spike.

If you don't have the means to get a good battery, if I were you and need to prevent these kind of things - which normally should not happen - I would do the followings.

Depending on the charging final voltage, I would use a power diode (battery isolator) and a set of unmannaged cheap gel/agm batteries (4s 12V/5A) in parallel with the main lithium battery.

In case of the main battery disconnect, the gel batteries will still be able to absorb, for a short period of time the spike, until you make some automation to shutdown things.

Also the diode will prevent the additional gel battery to be discharged on the main battery.

Of course, you can do whatever you want with the energy stored in the agm batteries, power up some other things.

Alex

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