2kWp panels (Not installed yet)
MPPT 150/70 (Not installed yet)
Cerbo GX
Multiplus II 5kVa
2.5kWh BYD battery with canbus comms unit (Its a start )
So the problem I am currently experiencing, if I trip the mains breaker (2pole) in the DB board, the inverter carries the load EVERY time with out a hiccup, the problem is when load shedding comes along the power goes off, (the house goes dark) then the inverter turns off for 30/45 seconds and switches back on and carries the load for 2 hours 100% (just TV, lights etc. ~600W)
This time round is the 1st time I actually got some errors on the cerbo and VRM namely;
Low voltage VRM and cerbo
High DC ripple VRM
I will try tonight to be there when the power goes off and see if I can catch it.
The only thing I can say is that the wires on the battery are on the thinner size however they look like the stock wires supplied with battery (rest are at least 35mm^2)
Any suggestions on where to start looking, will take anything right now.
Where the inverter tries to power the whole street for a couple of ms before cutting the input. This is very different from the grid just disappearing when you trip the switch without pulling the voltage down.
You could try running without a grid code and turning on the UPS function and then definitely NOT USING the ESS assistant, i.e. just as a backup UPS. (I’m unsure of the legality of this, but it’s safe as long as you don’t use ESS.)
If that solves your problem, you could install a voltage protection relay to cut the grid faster. Keep an eye on what @TheTerribleTriplet is doing, he’s having one installed soon (but for a different reason).
DC Ripple is bad. The first thing is the battery cables and their connections. I would upgrade the cables from the batt to the inverter to Victron specs if you are having issues, and nothing else is found. Would also check every single DC connection that they are properly tightened/crimped.
Do it. Grid code is good for Carlo and Cerbo combination.
No grid code is not a good idea unless it is a UPS only, but there are panels, so you have to do it in any event. Use the opportunity to complete the install.
Find the cause, don’t “panic” and do too many things.
Just remember you need a password for that, which I don’t have. Ask for it earlier, or expect a private message from someone I hope
Nope. The Multi does that itself, the ET112 is for the Cerbo to be in the loop, but it’s much slower.
Not running ESS might make it faster, I’m not sure. But your actual problem is not the overload I pointed to, but something on the DC side.
Agreed. But might work as a troubleshooting step. I agree with everything TTT said, IF the no-grid-code helps, you cannot leave it like that (edit: and add ESS). Find the actual problem. Slow & meticulous.
The rest of the symptoms sounds like the BMS disconnected the DC bus. That explains both the low voltage alarm and the ripple alarm.
The 30-second turnaround is also normal. That’s what it does after an overload, which is what happened here.
I’ve heard that in a few places in the country, the grid doesn’t just drop out immediately… it has more of a “brown out” happening. One solution I’ve heard of is to actually raise the voltage where the Inverter takes over so it cuts out quicker. But that will require switching the grid code to “other” and setting your own parameters. Which technically makes the installation non-compliant.
You can also, in the interim remove the ESS assistant (as @mariusm suggested), since the PV panels are not installed yet. This is completely legal. The Multi complies with all the codes required of a UPS, and in this mode it is strictly interlocked (either inverter, or grid) so none of the embedded-generator regulations apply.
So I raised the disconnect voltage to 210V (not set as UPS)… Sadly the power went off, low battery light came on, 30s later power up. Cant be great for the equipment.
Bit more digging here, does the inverter follow anything DCL says (i.e, DCL=50A) other than DCL=0.
I know it follows CVL and CCL (at least the upper and lower limit) and is it inverter mode dependent, such as Keep batteries charge, BatteryLlife on/off
When the grid fails, the inverter ignores DCL, except for DCL=0. The reasoning behind this is fairly simple. Imagine a few hypothetical cases: DCL=35A, but for a short period of time, you are doing 40A… inverter throws a tantrum and switches off. How irritating is that? Vs, the inverter allows the excursion, but then the battery heats up and the BMS switches off. Still irritating, but a lot more understandable. The BMS is the final arbiter.
But as I understand it, you’re wondering if the DCL value could affect the overload-at-grid-failure issue, and the answer would be that it does not affect it. DCL only applies when there is an alternate source of energy (the grid).
Thanks, I agree in off grid situation its all about giving 100% regardless.
As you know the battery most likely was disconnecting when the grid failed due to the battery BMS, and I had the system on Keep Batteries charged. This got me thinking it trips when it thinks the grid is still up (going down) and ESS will try off set the load i.e. the entire street for X mS.
I have since changed the mode to battery life disabled and set the max discharge power (cannot set this in keep batteries charged, I guess that makes a little sense 2%) to initially 1000W in increments of 250W after every successful load shedding event up to currently 2000W currently (tonight at 6pm will be testing 2250W) and the system now works 100% every time (Very happy ).
What I don’t like about this approach is that once PV is added the system will be hard limited to X max discharge power, however as the battery is only ~2500W DC capable not a huge train smash as keeping loads below 2000-2500W AC isn’t that hard (Doing that with my 3kVA)
So if I can get to ~50A ~2500W on the DC side (~2250W AC) and its stable why did keep batteries charged not work as the DCL of 49A is set.
The only time slot I see with a low battery alarm is at 4:09AM on the 17th of November. And that’s because the battery was unhappy about something. It fleetingly asked for both CCL=0 and DCL=0, which usually means it is in some kind of error state. That is interpreted by the Multi as a low battery condition and it raises the low voltage alarm (although the voltage was a healthy 54V at the time).
But the battery reports a DCL of 49A most of the time, or around 2.5kW, so it sounds to me like you have a single 2.5kWh module in that battery. That’s too small. You need to size it for off-grid use, which means you need 3 modules.
The BMS in the B-Box Pro activates a contactor, which completely disconnects the battery from the DC bus. That’s why the ripple warning came up straight afterwards.
The only time slot I see with a low battery alarm is at 4:09AM on the 17th of November. And that’s because the battery was unhappy about something. It fleetingly asked for both CCL=0 and DCL=0, which usually means it is in some kind of error state. That is interpreted by the Multi as a low battery condition and it raises the low voltage alarm (although the voltage was a healthy 54V at the time).
That’s the only time I got any VRM logging when load shedding happened and it all fell to pieces, and I only think because I had the internet on a UPS. After that point you will see I moved to batterylife disabled. Every time before that the downloaded logs have gaps of 30s to 90s when it crashed.
But the battery reports a DCL of 49A most of the time, or around 2.5kW, so it sounds to me like you have a single 2.5kWh module in that battery. That’s too small. You need to size it for off-grid use, which means you need 3 modules.
I agree its too small, however for mostly loads of <500W it should be okay for load shedding, as we aren’t expecting to be in load shedding forever (what 2 months in now???) it however was the cheapest way of getting a Victron setup (2nd hand, from a clearly badly put together equipment) however I know the limitations and can automate around them with to off set most loads and some small battery backup, ideally upgrade just need to make do for now.
This all may just be a symptom of too small a battery, however its the niggling my brain why 100% battery overload under keep batteries charged (13th to 17th) and 100% success on battery life disabled when load shedding hits (18th to now).
But since this is the load profile so far… with loads never really above 2kW… another option might be a smaller inverter to match the battery.
I would ideally prefer to limit the inverter inline with the battery for now, this is a ~300 to 400kWh/Month house.
I know why. Your GX device dies when the trip happens, because your whole DC-bus goes out. And because the grid also goes out at the same time, there is just nothing keeping anything powered.
I don’t think limiting the inverter inline is going to help. The physical bulk of the thing, of the transformer it needs to drive, is such that when the grid falls out, a large current spike will flow out of the battery. In an ESS system, the grid is in parallel with the battery. When the grid falls out, energy will flow outwards for a short amount of time, it is unavoidable.
Your only option here would be a non-ESS system, I think.
Yip everything disconnecting will make power disappear, thanks though.
So any last insight to the limiting inverter to <2001W seems to be working 100% but keep batteries charge doesn’t ever work in this case.
… another option might be a smaller inverter to match the battery.
I like that idea, my only option here would be to swap for a 3kVA multigrid, I know specs still say you will need two batteries, however that’s the only option available. What are your thoughts
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