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porcini avatar image
porcini asked

Using Multiplus SOC-low-shutdown with BMV SOC value

Hi all,

If I update my Multi to the newest firmware I could use the new feature "SOC-low-shutdown".
In past I used to take the BMV-relais for that, but now I am wondering if this would also be possible with a software solution.

In VEConfig I have to enable the battery monitor of the multi to use this feature. So the question now is:

Can I use the Multi's SOC-low-shutdown feature by using a venus device which overwrites the VE.Bus SOC with the one from a BMV (or BMS)?


Normally I would just try it, but there is no reason for an update if this won't work :)

Thank you!

MultiPlus Quattro Inverter ChargerBMV Battery MonitorSOCVEConfigure 3
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7 Answers
porcini avatar image
porcini answered ·

I tried it today. Here is the answer:

It works with the Multi's battery monitor as well as the BMV's/BMS value when "Synchronize VE.Bus SOC with battery" is enabled.


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Paul B avatar image
Paul B answered ·

I think you will find that this only works with the Internal multi/quattro battery monitor, not the external monitors ie BMV

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boekel avatar image boekel ♦ commented ·

Are you sure? Venus writes the SOC to VE.bus I think.

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porcini avatar image porcini boekel ♦ commented ·

That's correct!

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stratanet avatar image
stratanet answered ·

Hey guys,

Sorry to dig up an old thread, but I haven't been able to find an accurate answer for this, and the information above is a little confusing. As you can see in the below image, there is no option of "Synchronize VE.Bus SOC with battery" on my setup:

I've deployed a few of these now, and ran into issues a couple of weeks ago when I discovered that the inverter was not shutting off the load based on SoC.

In this lab setup (as above), I have a MultiPlus 48/800/9 connected via a Venus GX, to a PylonTech US3000. The MultiPlus firmware is v475 and the Venus firmware is v2.57; both the latest as of this post.


-----
Silly me. I just noticed the "shut-down on SOC" option below as I was proof reading this post! So the rest of this post may be pointless. OR it may help someone, which is why I'm still posting anyway. The rest of this post I'll leave as it is, based on what I was trying to find out. I'll test and report back on my findings.
-----

So can the inverter in the MultiPlus be triggered to shut off based on SoC, or does it have to rely on voltage? I haven't accurately setup the shutdown voltage on VE Configure in this bench setup, as there is not much point due to the little amount of voltage variation presented with Lithium batteries:


Any help in this matter would be kindly appreciated. I've got about 20-30 of these left to do, so would like to get it right!

@Mark, your post here was very helpful. Perhaps you may have some insight on this? https://community.victronenergy.com/questions/19480/soc-differences-between-devices.html

Cheers.


venus.png (45.7 KiB)
multi.png (136.2 KiB)
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stratanet avatar image stratanet commented ·

So far setting the "shut-down on SOC" seems to work.

Note that from my discoveries so far, if there is grid power available, the AC output will be on regardless of the SoC setting (this is actually quite sensible).

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stratanet avatar image
stratanet answered ·

Hi all,

My solution above I've tested and is working. The "shut-down on SOC" feature is what you're after. For the sake of testing, I set "SOC low shut-down" to 79% and "SOC low restart" to 80%. My 500W dummy load was turning off and on just as predicted (remember as mentioned above, the load is always on when grid AC is supplied into the MultiPlus).

I don't remember seeing this SOC setting on older firmware - so make sure everything is updated and you should be good to go.

I haven't yet tested this with a BMV-700, but I'm sure the same theory applies.

Cheers!

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stratanet avatar image stratanet commented ·

Confirming that one of my devices on firmware v416 does NOT have the "shut-down on SOC" feature.

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PeterM answered ·

I am still confused with this discussion as I also want to do the same as Porcini , however to Enable 'Shutdown on SOC " on VE Configure - a warning comes up that you have to Enable the battery monitor - however on the Venus the BMV is set to "Automatic ". If you setup the Battery monitor on VEconfig is that not going to conflict the BMV ? Further it has a parameter "SOC when Bulk finished" which the BMV does not have and is irrelevant to Lithium cells

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stevesea answered ·

I'm also confused on this thread and hoping to get some clarification. I have a multiplus, a BMV 712, and a GX device. The GX device uses/displays the BMV information by setting (on the GX console) Settings > System Setup > Battery monitor = BMV 712 on VE.Direct. Then when I go to the MultiPlus settings using the VEConfigure (via a VE Bus to USB device), and I try to enable the Inverter > shut-down on SOC, it gives me a warning that I must first enable the MultiPlus battery monitor. However, as @Merle.Peter commented, wouldn't this use the MultiPlus battery monitor's SOC instead of the BMVs?


The people that says they could get it work (@porcini, @StrataNet), did they enable the MultiPlus battery monitor, then enabled the shut-down on SOC, and after they disconnected from VEConfigure assumes that the MultiPlus actually starts using the BMV SOC provided by the GX? If so, how do you know that's the case instead of MultiPlus simply using the internal monitor SOC (as the VE.Configure makes you believe)?

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radon238 avatar image
radon238 answered ·

I have been testing this for the last few days

When a Smart Battery BMS.Can is connected to the GX, the Ve.Configure Multiplus Shutdown on SOC works well.

The Only issue that I had was premature shutdown before SOC had been reached because my ESS Low battery shutdown voltages were set to high, and they did the shutdown before the SOC parameter could. After correcting this I reliably shutdown on my set SOC of 20%


On another system with a Smartshunt connected to the GX with a VE-Direct this does NOT work for me.

The Smartshunt does all the SOC calculations, and puts it on the Bus, but the Multiplus does not seem to react to this System Bus SOC Value.

GX Settings: Syncronize VE.Bus SOC with Battery = ON
Battery Monitor: Automatic. Auto Selected: Smartshunt


PS. When Enabling the Battery Monitor in Ve.Configure in the Multiplus it will calculate its own SOC. One thing to note is that It Resets the SOC to the Fixed Ve.configure value "State of Charge when Bulk Finished". So for instance if you set this to 85%, everytime it switches from Bulk to Absorb it will set its SOC to 85%.

In Contrast the Smartshunt and BMV resets their SOC calc to 100% only when a specific X Voltage has been held for Y time, and the current has dropped to less than Z% of Bulk

Here is a Victron video which explains more on this SOC calc: https://www.youtube.com/watch?v=mEN15Z_S4kE

Below is an example of this happening, although I don't know why it triggered the reset to 86% prematurely:

soc-reset-example.jpg


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radon238 avatar image radon238 commented ·

Just an Update:

Testing again on a Smartshunt connected to Cerbo GX connected to Multi, The Shutdown on low SOC works well.
The Multi's Internal SOC has the behaviour as in the Graph above only when charging, but it Syncs with the smartshunt's SOC value eventually.

During a discharge cycle I manually set the Smarthunt SOC to 22%, and the multi then shutdown a few minutes later at Ve-config "Shut-down on SOC" which I had set to 20%.

I think its shut-down works on it's internal Hidden SOC calculation, instead of the VE.Bus SOC value, but it syncs its internal value from time to time with the Bus SOC.


In the Post above I said: "So for instance if you set this to 85%, everytime it switches from Bulk to Absorb it will set its SOC to 85% ". This does not seem to be correct, as the Multi does this SOC set with some other trigger or Calculation.


Maybe the Victron engineers can shed some light on the Multiplus SOC calculation formula during charge?

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