8000VA Victron inverter + 5kwh BSL Battery. Possible?

Hi Guys

I have a customer that bought a Victron system from us with the idea of upgrading the system in the future with another 5kwh battery.
Space is limited.
His requested is a 8kva Multiplus 2 with 5kw BSL battery.
His essential load never reaches 3000w.
We are now running into a issue where when loadshedding start the system will shutdown, go into low battery error and will start again after a 30s -60s.
Maybe inrush current?
Any ideas on how to work around the problem?

Thank you

When loadshedding hits there is a fraction of a second where the MP2 tries to carry the entire street until it realises that the grid is out and opens the relays. I regularly get overload warnings when loadshedding starts.

With a 8kVA multi this momentary load is likely in excess of 10kW.

I would check that the battery cables are up to the task. If that’s not the issue then the single battery may not be able to supply the required current without the voltage sagging, and he may have to buy the additional battery now rather than later.


Do you think installing a AVS will maybe solve the problem?

We know the battery is too small for the inverter, so buying another battery is certainly a good idea. However, I would not throw money at something like an AVS unless I am 100% sure that my diagnosis above is correct and that it would in fact help (you can achieve much the same thing by tweaking the grid code settings of the MP2).

What happens when you simulate loadshedding by flicking the main switch? If the error only occurs with real loadshedding then I’m probably on the money and it is due to the high load when the inverter tries to power the entire street.

Is the low battery voltage error coming from the MP2 or from the GX device (BMS)? In other words, is the battery itself disconnecting from the DC bus, or is it only the inverter that is shutting down? If the inverter shuts down and the battery stays up then it could be something as simple as a low-voltage cut-off setting on the MP2 that is too high, and the momentary DC voltage drop is enough to make it trip. Thin battery cables will exacerbate this voltage drop, so thicker cables are better.

If it is the battery itself that is tripping then you can probably solve the issue by adding another battery. If you have a spare battery at hand you can temporarily hook it up in parallel to see what effect that has on the symptoms.

Of course, there’s always the possibility that you’re dealing with a faulty inverter and/or battery.

All that Pierre said, with one caveat:

You install a i.e. Tripconnect to protect the inverter better, and more importantly, the non-critical loads better with a Tripconnect installed on the main DB.

I installed it as per a Victron dealer/repairer, who suggested it.

Only if you’re running ESS. The original post doesn’t tell us if he’s doing that. If this is a backup-only system, then it is likely not running ESS. But the sudden transfer of the household load to the battery could cause a kind of inrush current issue, although I would not expect the voltage to brown out like this if the load is 3kW or less.

Restarting after 30 seconds is normal. That’s what the Multi/Quattro does, three times in a row, before it gives up.

This is a good suggestion! Again, when ESS actually is installed (we don’t know :slight_smile: ), the inverter uses the Dynamic cut-off curve instead of the low voltage setting, even when in islanded mode. If your curve is set too high, a sudden draw down on the battery could cause the inverter to see it as a low battery condition, and switch off. My advice is to set this curve flat at a voltage below 48V, ie just set all the values to 46V. This way the Multi will not switch off on low voltage, we leave that as an exercise for the BMS… should it want to.


Thanks for the info guys.

I am running ESS. Dynamic Cut-off is set to 47v at the moment. Will change and test.


47V, on a full battery, should be ample. But of course, when the grid fails it will for a split second pull a lot of current from the battery, so maybe it is indeed that. Can’t say for certain.