Victron Multiplus shutting down

[ttmetro]

Recently my Multiplus shut down and I wonder why this happened and how to prevent this in the future. By shutdown I mean the unit powered off and no longer passed shore current to the loads (power was not out at the time). The unit ran over 6 month without problems (taking over seamlessly during the many power outages we suffer here).

My setup is a whole house UPS. Shore power is the only source. Parts:

• Multiplus II 48Vdc, 120Vac inverter/charger
• 13kWh lithium with Overkill BMS

When the shutdown occurred, the Multiplus was charging the battery which was near full. Most cells were ~3.63V, but one cell voltage was ~3.7V. Presumably that cell (#13 in the array as luck would have it) has lower capacity and may need replacement. The BMS recorded an over-voltage alarm at 58.03V and may have shut down the battery. Neither of these conditions should shut down the Multiplus: it's rated for 38-66Vdc and does not shut down when I turn off the BMS on purpose.

Any idea as to why the Multiplus shut down and how I can avoid this in the future? At least it would be "nice" if it passed through shore power in this situation.

 

[Q-Dog]

Were there any flashing lights on the front panel?

 

[ttmetro]

Unit was completely off (no lights at all).

After turning Multiplus unit off and back on again (with the rocker switch), it immediately shut down again after rapidly "blinking" a few lights. Then I turned off the battery (a BMS option). Now power cycling brought the Multiplus back to life with the "low battery" light on. That made sense since I had turned off the battery before turning the unit back on.

An internet search point to a few cases of a Multiplus shutting off (https://community.victronenergy.com...s-shuts-down-without-any-apparent-reason.html), citing low battery as the primary reason. In my case the battery voltage was likely high (judging from the BMS' 58.03V high voltage warning). Then the BMS might have turned off the battery (although it should not have since the battery over voltage is set at 58.4V). Normally that won't shut down the Multiplus (I've just tried it), but perhaps it was still charging and got confused. Maybe the Multiplus would have recovered on its own after the battery came back online (if it indeed was offline).

I don't have a GX or other logger hence don't have a detailed record of what happened.

Presently my settings are:

Multiplus:

• Bulk & absorption: 16 * 3.6V = 57.6V
• Float: 16 * 3.25V = 52V (essentially disable charging during float)
• DC input low shutdown: 16 * 3.2V = 51.2V

Overkill BMS:

• Battery over voltage: 58.4V (56V reset)
• Battery under voltage: 49V (51V reset)

Perhaps I should increase the battery over voltage, e.g. to 59V (3.7 per cell). The Victron should never apply more than the absorption voltage (57.6V) anyway.

Thoughts?

BTW: I find that charging beyond 3.6V per cell results in >100mV imbalance that the BMS cannot handle. After charging cell voltage drops to ~3.25V after a while. Imbalance is only ~5mV, but this of course is the case even if they array is not well balanced.

 

[HRTKD]

Any luck finding the problem?

I would start with the connections. A bad connection somewhere can cause some very screwy results. Check every cell terminal connection too.

I don't have a Multiplus yet, just two Victron MPPT devices. I was using the 14.4v default but have since modified that down to 14.2v, just to be a bit more conservative. I'm also using the Overkill Solar BMS, but 12v.

 

[ttmetro]

Shutdown happened only once, so it's a little difficult to diagnose. I doubt that connections are an issue, all bolts are tightened to the appropriate torque.

Is there somewhere a document that describes the situations under which the Multiplus shuts down?
Presumably if it runs out of power - should it then automatically start back up when power (line or battery) comes back?
Other situations?

 

[rmaddy]

Is there somewhere a document that describes the situations under which the Multiplus shuts down?

See the Troubleshooting chapter of the MultiPlus user manual.

 

[ttmetro]

14.4 vs 14.2V is the bulk & absorption voltage?
This corresponds to 3.6 vs 3.55V per cell.

What does this do to balancing?
When I got the cells, I top-balanced to 3.65V. Presumably the reason of the relatively "high" voltage for balancing is the high slope of cell voltage versus charge.

At lower voltage, e.g. 3.55V, this slope is much lower (almost flat) - imbalance is not very noticeable. How does this compare to if I had balanced initially at this voltage (with presumably lower accuracy)?

More simply, what's the downside of balancing at 3.55V rather than 3.65V?

 

[ttmetro]

See the Troubleshooting chapter of the MultiPlus user manual.

The following issue listed in Section 7.1 (general error indicators) may apply:

Problem: Inverter operation not initiated when switched on
Cause: The battery voltage is excessively high or too low. No voltage on DC connection.
Solution: Ensure that the battery voltage is within the correct range.

If the BMS shut down the battery, the voltage could have been "too low". But then the low battery LED should have been illuminated. AC line power was available.

Has anyone experienced the Multiplus shutting down?

 

[HRTKD]

Balancing to 3.65v is normal. You don't need to get it that high after that. As far a balancing cells goes, consult your BMS parameters to see when it starts cell balancing.

Break out your volt meter and check the voltage at all your connections. Victron is very reliable, so I would lean toward the Victron being right. There are rare cases where Victron equipment had failed, but I bet I could count on one hand (or maybe one finger) the number of Multiplus failures posted here on the forum.

 

[Q-Dog]

All I can think of is the multiplus, for some unknow reason, may have rejected the grid connection when the battery disconnected. If neither the grid connection nor the battery are available it can't run.

¯\_(ツ)_/¯​

 

[adambant]

I am seeing identical issues with my Multiplus-II 48v system. 15.5kW LiPO4 battery and DALY BMS. I know my BMS isn’t cutting off because it is a passthrough type and would cut of DC power completely. I am getting “Excessive DC Ripple” alarms on the Victron console when it is happening. I see the DC voltage jumping around ALOt when the MPPT charger reaches absorption phase. If I turn off the battery charging on the MPPT is settles down and stops shutting off. I have checked every connection and can’t figure out what is causing the ripple at top voltage.

 

[ttmetro]

I just had a second shutdown. This time I was on vacation. I'd really like to figure out how to prevent this - a UPS that cuts power off (fridge etc) isn't really useful.

I don't have a "Victron console" (is that a GX?) and hence do not know what led to the shutdown. I also did not find anything in the manual that or why this would occur.

After power cycling the unit it came back on and started charging the battery (which was almost full). I've noticed that one cell reaches max voltage sooner than the others and before the entire array reaches the absorption voltage (57.6V). Then the BMS switches off charging, balances the cells, and resumes charging. This happened multiple times without the Multiplus shutting down. Hence at least in this case, this does not appear to be the problem. I also do not have solar - the Multiplus is the only device connected to the battery.

The Vicron community website has several references to similar issues, e.g. https://community.victronenergy.com/questions/50634/multiplus-ii-48v-3kva.html.

Possibly a firmware update would solve this issue - has anyone tried this?

 

[cfsmith]

Did you ever figure out what was happening?

 

[ttmetro]

I think it was due to battery voltage. Changed settings, never had the problem again.

 

[adambant]

Too funny, this sounds almost exactly like an issue I was having. Even down to the battery #13 being the problem battery in the equation! I have a Daly 250A BMS however which is a pass through BMS type. The one cell was causing high and low voltages that was tripping the BMS to shutdown effectively turning off my Multiplus II 48/3000. I had a bad cell in my original pack and used (what I thought) was an identical 280aH EVE cell as a replacement on the original pack build. For the first year it ran great, over time that mismatched cell started to deviate and cause issues under high current loads and charging causing the BMS to trip. I temporarily got around it by adjusting the allowable high and low voltage margins before it will trip now.