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jeff925 avatar image
jeff925 asked

Multiplus II inverter shutting down at 100% SOC showing ESS Mode 3

My inverter is shutting down when the battery is fully charged (98%+) and the GX display shows "ESS 3" above the battery.

I have a Multiplus II inverter, a Smart Solar MPPT, a Cerbo GX, and a 100AH 48V battery with CAN-bus BMS communication (Trophy Battery). This is an offgrid system with no ESS assistants programmed. Everything was working fine until my battery reached full charge today and then it started shutting down my inverter repeatedly.

I have the battery controlling the charging with DVCC settings in the Cerbo. Is there some reason the battery would tell the inverter to shut down when it is fully charged? The inverter is only seeing 50-100W load so it is not being overloaded.

I'm happy to provide more info but don't know what is needed at this point so let me know. Thanks

Multiplus-IIcerbo gxESSDVCC
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6 Answers
matt1309 avatar image
matt1309 answered ·

I'd try monitoring the BMS when you reach that scenario to see if there's any limits being reached ie over voltage etc.


It may be a case that the absorption voltage is a little too high and a cell within the battery pack is peaking over, the overvoltage limits causing inverter to shutdown? Random guess but worth checking given BMS comms are connected.

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jeff925 avatar image
jeff925 answered ·

I turned off all the BMS control on the Cerbo so hopefully it will just work like a traditional system with the charge limits set in the MPPT and Multiplus. When I have time, I will try monitoring the battery and looking for outliers.

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togopg avatar image
togopg answered ·

Hello,

A few weeks ago I had a similar problem with one of the systems:

The inverters were going to "Off mode" without any other alarms except "Low battery voltage".

In this condition, the inverters failed several times at different SOC levels.

My colleagues and I continue to monitor the system but they have not shut down the inverters recently.

screenshot-20230601-062340.pngscreenshot-20230601-062420.png

Although, I haven't had a similar problem recently, I'd be happy to learn what caused it


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screenshot-20230601-062420.png (68.6 KiB)
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seb71 avatar image
seb71 answered ·

In a system with ESS, the status code ESS #3 means "BMS disabled charging".

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jeff925 avatar image jeff925 commented ·
That makes sense, but why would charging disabled turn off the inverter? Does it also disable discharging? There wasn't a ton of sun at the time so as the clouds came and went the inverter wouldn't have had enough power from the charge controller. I didn't see any error messages or warnings though.
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seb71 avatar image seb71 jeff925 commented ·

Yes, the inverter should not turn off just because the battery is full.

I just mentioned that code (just in case you did not knew it already) as a possible hint for where to look.

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Alexandra avatar image Alexandra ♦ seb71 commented ·

@jeff925

It is very possible that the battery is disconnecting itself entirely from the system because it is unhappy.

Some batteries can control charge and discharge separately, some disconnect entirely with a contactor. Since I am not familiar with your battery I can't say for sure.

Check in the vrm advanced under DCL and CCL widget.

@togopg this might also apply to your battery.

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jonathan-drewes avatar image
jonathan-drewes answered ·

Hi Jeff, I just saw your post here as I was about to make one about the Trophy battery with my Multiplus2.

What I bet you are experiencing is what I had trouble with (and still would) a while back.

trophy shutdown.pdf

Read through my notes on this in the attached. My solution to this problem is to use a fixed 15min absorption time so that the battery cannot report 100%. Usually, it reports 97-98% after absorption (its actually at 100% then).

I would like Trophy-Dan to have a fix for this but so far there is none.

Also, look how far my Trophy SOC is compared to the Victron Smartshunt.

1689706068600.png

1689706093325.png

I know the Trophy reading is wrong so i just use the Victron SS. Its annoying.


1689706068600.png (35.8 KiB)
1689706093325.png (55.8 KiB)
trophy-shutdown.pdf (534.5 KiB)
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jeff925 avatar image jeff925 commented ·

Interesting. Yes, I have been in contact with Dan as well. The day I emailed him about it he said he had just spent all that day testing trying to figure out what was going on with this issue.

His suggestion: Use DVCC and set maximum charge voltage to 54.7V. Turn on Limit managed battery charge voltage. SCS = ON, SVS and STS = OFF, limit charge current = OFF.

I did this but my battery would limit charging current well before 100% SOC and just slowed down my MPPT or generator. I decided to just set the maximum charge voltage to 56.8V and I haven't had it shutdown again but I haven't had it that way very long to know. It will drop the charge current to maintain that voltage and seems to do OK. My system doesn't have enough solar yet so I run the generator a lot so I'm not sitting at 100% much.

I wonder if this is related to the battery reporting an incorrect/different voltage compared to the rest of the components. I noticed the reported voltage is lower than my MPPT for example. So maybe it is trying to push the battery voltage too high and the the BMS cuts out?

I have also noticed that the SOC is significantly off as well. I don't have a smart shunt to compare it to but I'm probably going to get one because this seems pretty bad. The SOC gets further off the longer it has been away from 100%. This seems to be because the BMS doesn't record power very accurately and low current draws (DC loads and inverter idle power) aren't accounted for. I find that my actual state of charge is HIGHER than reported (usually 10-15% and occasionally more). I think the battery is over-reporting my small loads.

If I run into this issue again I will try the absorption time as well. I see in your thread you were looking to replace the BMS. Did you do that?

I kind of wanted this system to just work but that's not been the case with this battery. I guess it was just too good to be true. Dan is very responsive I'm just not super impressed with the battery itself.

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jonathan-drewes avatar image jonathan-drewes jeff925 commented ·
Dan sent me a new battery, not a BMS to swap. The new battery does the same exact thing. What I believe is needed is to have the Chinese BMS supplier look into this issue and resolve it. Also, the SOC error too.


Also, I tried all kinds of things, settings to solve this along the way. So far, the only solution is to not let the battery get to a self-reported 100% SOC.


Yes, the BMS SOC error grows over time. That is why I try to get it topped off each day using solar.


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jeff925 avatar image jeff925 jonathan-drewes commented ·

Yes I agree, it would be nice to have a reliable fix for this!

I charged my battery up with the generator and finished it off with solar today and it was at 100% SOC (as reported by the battery) for a little over 30 minutes with no disconnect issues. It is now hanging out around 98-99%.


I just don't think I can trust it. I'm going to be gone next month for a few weeks and I would like to be able to water my garden/fruit trees automatically but I won't know if this thing is working or not (I don't have a constant internet connection to check VRM). I guess my neighbor will have to keep an eye on it...



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jonathan-drewes avatar image
jonathan-drewes answered ·
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