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AGM voltage drop under load with high SOC - Multiplus 2

I have a Multiplus 2 with a smart shunt and five 100AH AGM batteries connected in parallel. I also have solar panels with two MPPTs that charge the batteries when not on shore power.

The problem - the batteries can be at a full state of charge with a voltage of 12.8V. If I run a heavy load like the microwave, the voltage will drop instantaneously to ~12.1 volts which will cause a low voltage alarm to trigger. When the heavy load is removed the voltage returns to 12.8 volts.

I measured the voltage at the batteries and confirmed that there is less than 0.1V drop between the batteries and Multiplus 2.

Is there some way to dynamically set the low voltage cut off based on the battery state of charge to prevent this from happening?

I don’t want to just lower the threshold since under a light load and low SOC the batteries would be over discharged.

I appreciate and help that you can provide.

Thank you,


ralphd asked
derrick thomas commented ·

4 Answers

MultiPlus II shuts down when grid fails

Note: please see my latest update for additional information and findings.


Hi all,

I've been having issues with my MP2 since installation. Every so often when the grid fails ("load shedding", substation trips, etc.) the MP2 shuts off for about a minute before starting up again).


  • 1 x MultiPlus-II48/5000/70-50 230V
    • Firmware: v490
  • 1x BSL Battery LiFePO48 Battery 8.2kWh (160Ah)
  • 1 x SmartSolar MPPT 250/100-Tr VE.Can
  • 12 x LONGi 450W mono panels
  • Cerbo GX
  • ET112 Energy Meter

At first I suspected a battery (BMS or otherwise) issue, due to the fact that the shut off coincides with "Low battery voltage" warnings and alarms, as well as "High DC ripple" warnings. There's a whole thread about this. I however do not believe this is actually the issue, but rather just a symptom.

A battery supplier technician was on site a few weeks ago to inspect the battery, and reported that everything seems fine (checked battery params via RS-485). He said:

There's a known issue with the MP2 and BSL and FreedomWon batteries. The MP2 has some low voltage offset bug where it would shut down on a battery voltage that isn't actually too low. The issue has been reported to Victron.

He suggested the installer set the "DC input low shut-down" lower as a workaround for now, until Victron fixes the bug. They set it to 46.80V (at this point the BMS should shut down the battery in any case). They also checked all wiring and replaced all fuses as a precaution.

After this, the issue seemed to go away. There was a "Low battery voltage" warning at one point, but no alarm and the system didn't shut down. However, last night when the grid failed (minisub explosion led to panel trip at substation, i.e. probably brownout) the MP2 shut down again for a minute. What is very strange is that there was only a "Low battery voltage" warning - no alarm. I don't understand why it shut down on a warning.

I am skeptical that the cause of the issue is actually a MP2 bug, since this happened on v481 and v490 firmware. Does anyone know about this bug?

EDIT: I just realized that the MPPT reported a large drop in battery voltage - see the VRM screenshots I replied with. It shows a voltage drop to 46.58V, which is well below the 46.80V DC input low shut-down. I measured the voltage on the battery terminals and at the MPPT with a multimeter. The battery terminals currently measures 53.7V, while the MPPT battery terminals measure 53.9V. Does this seem okay?

My theory of the actual root cause:

- I've seen threads about similar issues, such as this one: MultiPlus II overload on grid failure. One comment that stood out:

Hi. Solved a similar problem. If you have No grid code set please set you Ac low disconnect to 195vac of even 200ac....low reconnect from 202ac and above. Where i am in Zimbabwe my grid is above 240ac sometimes on failure it browns out as low as 170ac! Unless you install some external capacitors the Mp2 struggles to get into inverter mode from such a low voltage to raise it to 230! HENCE DC RIPPLE SHUTDOWNS..LOW BATTERY LIGHTS.and BMS SAFETY SWITCH OFF..etc.

- I have a feeling that when the grid fails (often due to equipment failure) the grid actually experiences a brownout. Then the MP2 tries to follow the voltage down, and finally attempts to switch over to inverter mode, but now the voltage is low enough that it struggles to reach 230V, draws a large current on the battery (thus causing a voltage drop), and shuts off.

- The "AC low disconnect" is currently set at 200V, but maybe this is still too low. The grid runs at anything from 235V - 251V. Should I maybe set the low disconnect to 210V or even higher?

- An external energy meter is beings used via USB (ET112) on the Cerbo. Could it be that it is too slow, and when the grid browns out the MP2 actually follows the grid below the "AC low disconnect"?

- I checked the BMS warning & alarm history via RS232 and PBMS Tools. There is only one alarm in the log since I purchased the battery, and that's when the "Low battery voltage" warning occurred without the system shutting down. The BMS reported a "SCP" protection (which I assume is Short Circuit Protection). Is this maybe due to a large current being drawn? There was about 4500W that was being drawn at that point, but the battery is 160AH @ 1C, so it should easily be able to handle that.


Does anyone have any ideas or suggestions? The installer has been on site multiple times and they can't figure it out, so I don't know. Should I maybe just insist that they replace the MP2 and battery?

P.S. screenshots of system configuration to follow.

anrich asked
nickdb commented ·

8 Answers

Is VRM down?

Is VRM down? It says I have no active installations

banne asked
banne commented ·

7 Answers

Multiplus II 12/3000/120 shuts down

I know there has been similar questions but I could not locate the fix for my unit. VMPII with 3 Battleborn batteries, VE bus smart daggle, and Victron battery monitor. My MPII kills power to my RV randomly but immediately comes back on. No faults, no power fluctuations, no overloads or patterns. I have had it for almost two years and it has done this since installation. It does it once a day to once a week to once every two month-random. I know it is the MPII because I had it installed in my previous RV and as soon as I moved it to my current RV it continued. I just loose 120v appliances. Any help would be appreciated.

edontheroad asked
rata1 answered ·

1 Answer

Multiplus II 48/5000 (240v) in Parallel and I am getting "High DC Ripple: Warning"

I have a pair of Multiplus II 48/5000 (240V) in Parallel and I keep getting a "High DC Ripple: Warning"

well I say 'keep gettting' it's happend twice, once when a high load switched off (kettle)
but also once when we were just ticking over at 300w

before some helpfull person says read the "Wiring Unlimited book".
I have, thanks !
the battery cables are short and a good size, and we did our best to make them all the same lengths

AND my question is:
what is the best way to monitor the system.

I don't know if it is relevant, but the slave seems to be louder than the master, (as if it's working harder) is there a way to monitor the out put of each unit separately ??

and/or is there a way to tell witch one is tripping the warning (master or slave)


iammotorhomeless asked
nickdb commented ·

1 Answer

Start up and Shut Down Process

Can someone please tell me what Startup and Shut down process they do, I want to try and do a laminated procedure, my setup is as below but I have got a 63amp MCB on the output critical load of the inverter

I was thinking house and garage RCBO’s off, 63amp critical load MCB off, then inverter and then batteries and start up in reverse?


daza asked

0 Answers

RS Smart Solar: Shut-down and restart behavior

I am planning an (completely) off-grid solar EV charger for my garage. I am new in solar systems, but I have a background in electrical engineering. Just a few questions concerning the shut-down and restart of the RS Smart Solar (and in general solar inverters):

  1. Shut-down due to DC input voltage below low battery shutdown level in practical terms means that it shuts down during night? [4.4.2. in the manual]
  2. Could it happen that on a bad rainy day the inverter is constantly switching on and off, because DC input is always somewhere between shutdown and restart level?
  3. What is actually meant by "shut-down", as the MPPT is still working and loading the battery, if possible?
  4. If the battery is full and the inverter is shut-down (during night) I could not supply any AC load?
  5. The inverter restarts based on the charge detect level, but also on the (re)start voltage (as implied by the paragraph on external MPPTs)? [in the technical specification the charge detect level is not mentioned, and the restart voltage is called start-up voltage (if that is the same)]

Sorry for the multiple questions, but I feel they cover the same topic.

helmut51 asked
helmut51 answered ·

2 Answers

Pylontech - shut down 40% SOC - impossible de descendre plus bas ?


J'ai installé un Multiplus II 48/300/35-32 et deux Pylontech US2000C. Je viens de m'apercevoir que je ne peux pas descendre en dessous de 40% SOC et je souhaiterai descendre à 20% SOC de décharge. J'ai utilisé les réglages recommandés, DC input low shut-down 44V, peut-on descendre ce paramètres et si oui jusqu'à combien ?

Ce serait occasionnel de descendre entre 20 et 40% SOC mais cela me permettrai d'avoir une marge de sécurité, je suis en food truck et j'ai peur qu'avec les fortes chaleur à venir ma consommation explose.

ked asked
yann answered ·

3 Answers

#1 error but no traceable cause

15kVA 3 phase 5kVA multis on v495

CCGX v 2.92

2 x Blue Nova 8kWh + 1 x Blue Nova 4kWh (stable, believe it or not!) Each wired to DC bus.

Virtually offgrid as grid is never present in the day.

Issue takes place in daytime only

System shuts down randomly, after 5 to 10secs it boots up again after throwing #1 device switched off error.

I checked all comms cables with cable tester, no problems

I checked VRM

Loads were half capacity max at any time even hours before the situation, but generally loads were 450W on the Phase that appears to be the one switching off - phase 2 (the middle inverter flashes a light sequence, where the other 2 do not)

Phase 2 gave an overload warning moments before first switch off, power was never higher than 500W at the time and hours in the run up to the issue.

There's no abnormal temperature going on either.

Am totally lost as to what is causing it. System today switched off 8 times in space of 3½ hours.

Help would be much appreciated..

Talfan Stamps asked
Talfan Stamps commented ·

1 Answer

RS 48/6000 Smart Solar Inverter - #29 overcharge protection issue

hi there!

I upgraded my system with the inverter in the title, and I have trouble setting it up correctly with my system, problems I have so far:

>solar charger will not start charging even though it has energy.

>not sure how to setup batteries, I have lifepo4 ones (4 in series) and they have a rudimentary bms, which is not accessible from the outside, no BT or CAN or similar)

>I decided to keep the solar charger (smart solar 150/70) of the prior system connected, currently it is charging the batteries, but the RS will seemingly randomly shut down

so about the shutdowns: in two days I got the #29 "battery overcharge" error code twice, yesterday noon when the solar charger (of the smart solar unit, mind you) went into absorption mode, and voltage was 56.80V, interestingly the RS showed slightly higher values than the solar charger. also the 4 series 12v batteries were not perfectly balanced yet, I have since installed 3 battery balancers from victron, and they are dead on balanced since yesterday evening.

so the second shutdown was weird though, it happened when there was little to no sun in the morning today, the batteries were at about 75% and the voltage was way off the maximum. this led me to try to dive into the menus to fix the issue, and to try to feed the MPPT of the RS instead, but as initially pointed out, I did not even get it to charge at all, not sure why.

so to sum it up, this unit is a bit weird for me, I used to have a cheap chinese inxiii 2400w 24V inverter which workes flawlessly without a single shutdown since about october in my old 24V system, with 4 of the same batteries.

what's happening here?

two thoughts I had:

>maybe I need to change battery preset to anything but lifepo4, albeit my batteries are lifepo4.

>maybe I need to find a way do disable the BMS? why does and inverter have a bms anyway? I was not aware of this initially.

any hints tips or an outright solution would be highly appreciated. if some pro could give me guidance on how to setup the battery that I have (for which there is not preset) that would be awesome.

I had no issues setting up the battery with the smart solar 150/70, but it doesn't have fancy bms tech, either, does it?



p.s.: I can't leave my home rn, as a fridge sits on this inverter, and when it decides to protect me (forced protection seems to be quite trendy these days, especially by governments) even though the BMS inside my german made (no, not german assembled, but german made) expensive lifepos is doing a nice job with overvoltage, overcharge, undervoltage, undercharage, overtemp, and undertemp protection.

p.p.s.: some more thoughts/observations:

>battery voltage measurement is exactly 0.05V higher from the RS than either the smart shunt or the MPPT150/70 during charging, I think it is about the opposite (lower by 0.05V) when discharging, but I will report back on this in the evening. what could this indicate?

>just checked in the RS' history tab, there are three errors, some hopefully due to me installing and connecting things, cause I never noticed them before, the are: #29 overcharge protection (we know this one), #10 battery low voltage (probably cause I disconnected the battery when connecting the balancers) #53 Inverter internal DC level (curious about this one). the main takaway here though is the max recorded voltage of my string of 4: 56.96V, which even if the RS shows .05V more than the other devices, is still "only" 14.24 per battery, which has an end of charge voltage of exactly 14.4V, according to spec-sheet. so again, what's happening here?

> is it possible the RS is not really designed or compatible to be used in inverter only mode, with a separate charge controller like I do? to me it seems the RS somehow "thinks" "look, the battery voltage is rising while I am not charging it, so it must be faulty? better shut it down" and then shuts down..?

billcarson asked
billcarson commented ·

0 Answers

Three phase system shutdown on auto gen start


This three phase system connected with a 40/28 Freedom Lite lithium battery recently shutdown and starts up whole system on auto generator start after sensing low SOC. Please what is the possible solution?

noah asked
Alexandra commented ·

1 Answer

Inverter switched off when CANBUS disconnected


I have a Batrium BMS That is connected to the Cerbo gx using the CANBUS. The BMS has a an issue where it freezes for an undetermined amount of time then restarts normally. When it freezes for more than one minute (not sure the exact duration), my inverters turn off. As soon as the CANBUS data is back, the inverters turn on.
Is there a way to program a delay before the inverters turn off?

Salim Naufal asked
Salim Naufal answered ·

2 Answers

Procedure for updating DC wiring with running inverter

Dear community,

can you please point me to the recommended procedure for updating battery-side wiring (adding MPPT to an emergency power system) with minimum impact on the loads? Would it be enough to switch off inverting (physical switch on Quattro) and disabling charging (VEConfig), then switching of the (Pylontech) batteries? Or would this lead to the grid throughput be switched off anyway, as the Quattro is not designed to run w/o batteries?

The system is powering two flats, I would like to reduce impact for our tenants. The work itself will be done by a qualified electrician.

If switching off the batteries is not an option, maybe it is a good idea to add circuitry to optionally "bridge" the Quattro with a transfer switch, and then switch off the Quattro completely? It seems to me that this would ease maintenance. Any issues with that?

Thank you.

tobyfw asked
Alexandra answered ·

1 Answer

Multiplus shuts still shut off when battery was empty and them 40% full


After grid shuts down, my BDY LVS battery turn to 0% (battery was empty). And the Multiplus turns to default. Then the battery runs to 40% with the 2 MPPT 450/100 (Multiplus still off grid). But the Multiplus was still on default (off). After switch off and switch on the Multiplus was working properly (no more default).

Why the Multiplus did not restarted alone when the battery was recharged at 40 % ?

(the SOC was set at 30%)

synelios asked
Alexandra commented ·

0 Answers

Campervan Electrics Setup not working correctly

Hi everyone,

We are having problems with two issues:

12v power - It keeps shutting down in the evenings even though the battery says it still has 90% power and we hardly use electricity, just to charge phones.

230v power - Every time we use the 230v plug sockets the inverter shuts itself off and we have no electricity whatsoever until the next day when it’s sunny. It shuts down the 12v power also.

Can anyone suggest where we are going wrong please?

This is a list of all the items we have in our set up:

80w solar panels x 2

60w solar panels x 4

Victron Inverter 12v 3000VA Sinwave (the cables are the right thickness & length as instructed)

Victron MPPT charge controller 150/60 -tr

Victron Battery protect 12/24-220A

LifePO4 TN 210ah battery

Victron Smartshunt 500A

Do we need 2 different MPPT because we have 2 different solar panels?

And are we missing any items from the circuit?

Hope someone can help!

Free Tammi asked
Free Tammi commented ·

3 Answers

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