question

Hi Jacko, see chapter 1.3 minimum voltage levels in this document:

https://www.victronenergy.com/live/multiplus_faq

I had this problem again last night, ive set minimum voltage to 215 volts do you think this is high enough or would you recomend higher again? I did have it set at 220 volts but i noticed the system was using less power from the genereator when running. It happened last night but the load was only under 2kW as seen in the images of the time the fault, so the batteries would only have has to take over at around 45 amps, any thoughts or recomendations?

whats the battery voltage doing at the point of change over is it going way low and the current way high. and what type of batteries do you have I presume that at 45% SOC they are LP

also are they on the latest firmware as this may help as well

Battery voltage was at 53.94 with generator running and fell to 53 as they took over the load, current goes from 183 amps going in to 0 as the system shuts down. Yeah there BYD 13.8 pro's. Quattros are on the latest 433 firmware im not sure if the BYD's are but they are all less than 3 months old.

Just a thought: can you check the battery Parameters in the remote panel when / just before this happens?
Imagine the batteries get warm and it adjusts it's charge / discharge limits.
How many 13.8's does the system have?

Thanks for your replys, batteries are in a temperature controlled room so always within a cpl degrees of 20 degrees c. currently the system only has 3 BYd pro 13.8's 4th going in this week, i know this is below the recomended amount in an off grid installation, but the site is never even pulling the full amount from 1 inverter (highest so far is 12kW), the site is due to increase in size so i allowed the second inverter to complete that side of install and all the equal AC and DC cabling straight away. Something i have noticed is about the LOM settings i left the grid code as none since its an off grid installation does anyone know if this would have LOM type A or B as a setting i assumed it would be dissabled but im fairly sure i was wrong now and hopfully this is the source of the probkem. I will change settings to UK grid code tommorrow and set as B if not dissabled, will post an update

Does anyone know if LOM is used to detect AC input with grid code 'none' selected?

Hi Jacko, What might the issue here is that the load has a bad powerfactor which the inverter gets to power as soon as the generator stops, which might cause an issue. Or there is a synchronization error. Make sure UPS mode and Weak AC are both switched OFF.

( i am sure you checked but the output neutrals on the inverter are joined at the inverters directly?!)

Hi @Johannes I had UPS turned on because i read somewhere that changeover would be quicker with it turned on but ive changed that now, I have the ouput neutrals and all other cables joined in the center of the two quttros so i could get equal lengths and equal resistances on all cabling. I beleive the sites larger loads are all resistive so i beleived power factor would be ok. I downloaded the CSV files from two of the times it happened and there was a couple of interesting things, on one occasion the frequency of the input falls as the generator shuts down from 50 hz to 42, the current raises 7.2 amps right upto 59.5 to supply the load of 2150 watts (that kind of explains the issue that time and ive unticked accept wide range of frequeny to try and stop a similar fault) the second time is not that obvious but i did notice that different parts of the on the VE bus see different things happening in the same time frame so some are aware the generator has stopped and gone into inverter mode but others like the battery current still see's it as current going into the batteries and battery state is seen as charging etc so maybe a slight delay in the information parts of the system beleive to be happening and bringing up a fault (not sure if youd class that as a synchronization error?)

Happened again last night:

UPS turned off ( although changing this to off as suggested by @Johannes seemed to help quite a lot for a while)

Min Voltge set to 218

Checked the CSV files there doesnt seem to be anything out of the ordinary other that the genertor shutting down loading is very low at around 700 watts charge current is at 196 amps in time bloack before fail. Battery monitor (which i think is gained from BYD's BMU) see's the system as charging for 3 seconds longer than the rest of the VE bus system when the rest has already decided there is a fault and shut down.

I really think a feature to ramp up and ramp down generator input would solve this as changeover would be less straining on the equipment would prob prolong the life of the transfer relay aswell.

@jacko I am experiencing a similar problem, so am very keen to know if you sorted your issue out and, if so, what the problem was? Thanks!

@jacko I have a very similar problem with my setup (May in fact be identical). So I am very keen to know if you found a solution and what it was. Thanks in advance.