question

Paul B avatar image
Paul B asked

Multiplus II 48/5000 Overcharging the batteries 59 volts and rising should be 54v

I Though this was solved yesterday but this morning away the sky hi voltages went again

MP II 48 5000 FW 459

VE BMS

Venus GX FW 230/51

BMV 700 Fw 3.1

DVCC was ON

ESS used and in position one on the assisstant list


The system voltage again last night just kept on increasing last night it went up to 59 volts, when float is set at 54.5 and absorption set to 56.3 in the MP II


The alarms were all going off this morning so I have just turned the mains off to remove the charging for the time being.


I tested this at 11 to 12 midday yesterday as per the graphs below and the voltage did everything it was supposed to ie upto 56.3 and all the cells then balanced to 3.5 volts and then the OV protect turned on in the BMS and the MP II disconnected charge and the voltage dropped away AS IT SHOULD.


then as per the VRM its just slowly increased again


Now EVEN with the BMS OV Protect TURNED ON using the VE-BMS ie the red led is on, on the VE BMS unit


With this on, ALL charging should be turned OFF why are we getting continual charging,


As the below Screen shots from the VRM


When the voltage went sky high and the charger was in float mode for the last 4 hrs, at the end it changes to inverter as I turned the mains off.


even form 1pm on you can see the voltage slowly rising but the OV on the BMS protection was still on as this is not released until the SOC reduces to 80% . SO the Charger should be off and no charge should be posable.


I have seen a few other posts with BYD batterys showing the same high voltage issue, but I cant see any resolution posted.



Multiplus-II
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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ commented ·

Hi Paul,

I had a look at the VRM.

The generator was in manual start mode? Why?

Once the generator is stopped, the AC frequency rises again, and the AC PV stops, and the system voltage stops rising.

If you have AC PV on this system, and also have a generator running, the multi cannot control the frequency to tell the AC PV to stop production.

Also the AC PV cannot export to a generator. So it must go to the batteries.


The same is also true in an ESS system if you have set a grid code that doesn't allow for export.

In this case you must use DC MPPT's or Fronius PV inverters (which have a Victron compatible zero export setting) for a stable system, this is described in the ESS manual here.



My suggestion is do not run the generator, or non-exporting ESS and AC PV on the same system when the batteries are 100%.

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Paul B avatar image Paul B Guy Stewart (Victron Community Manager) ♦♦ commented ·

Guy Tere is NO generator. the generator is just the way I turning the main grid off and on. As I turned it off this morning because of the over voltage

I in the past have removed the general flag that ignores the ac1 in but the same slow voltage rise occurs

the solar is grid tie to AC1 out and was OFF due to the freq rise only when I turned the mains OFF at 8.30am, plus this occurred at night so there was NO sun anyway, secound today I also turned the solar off fully so there was no output all day


The grid code use does allow for export and it does export unless there is a mains failure and then the grid tie unit turns OFF.

it was exporting fine yesterday when it was charged to 100% and it was still exporting most of the day.


You will also see that overnight the voltage has been slowly going up even though the High Voltage protect from the BMS was on, and all charging should be off,

I do agree about the grid toie issue but this was all yesterday afternoon and all last night the voltage just kept slowly rising


HOW ??? is got me really puzzeled


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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ Paul B commented ·

The graphs from VRM are showing a PV inverter yield at the time?

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

I've asked some others if they had any ideas.


The first thing they said was, return the unit to factory defaults (ie remove your assistants), update to the latest firmware and see if the issue persists.


That will at least help narrow it down.

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Paul B avatar image Paul B commented ·

Hi Guy Thanks for that and I have done those suggestions

I removed all assistants, and I did put back the BMS assistant as a basic one

FW is already 459


This 1.5 amp charge disappeared


I then added them all back one at a time

when I added back the ESS and removed the BMS assistant

the problem came back and I am now getting a 1.5 amp charge all the time. still / again


I did check the BMV shunt to make sure that there was a 1.5 amp flow using a INLINE meter and that was correct.

I tried changing the battery life options but still the same.

I repaired the Assistants, Still the same


Any further suggestions to try ????


PS the Solar did zero its self tonight but after the reset its now back at 75watts. no issue here as this will clear in 24 hrs, but its some how not holding its calibration after a reset, I tested this by turning the MP2 off then back on before it did all the above changes

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