[this problem has already been mentioned in a different discussion: Multiplus feeds in even though feed-in is disabled — but I’m posting this issue separately, because it might get lost in the other discussion]
Is there a way to tell ESS “no, really, seriously, I mean it, maintain a Minimum SOC of 15%”?
I have ESS set up with a minimum SOC of 15%. The grid (genset) gets connected at below 20%. But, as I discovered yesterday, ESS in fact DOES NOT maintain the minimum SOC. I was down to 10% when I caught the problem, with ESS discharging my battery even though there is a 15% minimum SOC limit and it’s set to “Optimized without BatteryLife”.
This happens with a specific load pattern: a small ~100W resistive heater that switches itself on every 20-30 seconds or so. The system goes from ~95W power consumption to around ~200W for 10 seconds or so. When the heater switches on, MultiPlus pulls some energy from the battery even though the grid is connected and the system is below minimum SOC (as shown on the dashboard). If I didn’t intervene, it would have been enough to drain the battery completely overnight. What I did was set the grid setpoint to 250W, which sort of balanced the battery draining with some recharging.
Is there a way to tell ESS to actually honor the minimum SOC setting? If it can’t regulate (as I’ve learned, the regulation in ESS is terrible), just switch to AC for the entire load, but don’t drain the battery!
Do you perhaps have your Peak shaving configured to “Always” instead of “Above MinSoc only”?
I ask because if peak shaving is only allowed above minsoc, the bridge inside the Multi is literally turned off below minsoc and it becomes impossible for energy to be fed into the grid.
With peak shaving set to Always, it will indeed always play catch-up and draw some energy from the battery.
The system will however go into the recharge state if the soc drops by more than 5% below the minsoc and charge it back up to minsoc, so this will not deplete the battery entirely.
I do! I’ve switched it to “Above minimum SOC only” now, I hope this will help.
Is there a way to manually turn this bridge off, or otherwise prevent ESS from consuming energy from the battery? This would be a workaround for my other problem ( Multiplus feeds in even though feed-in is disabled ) where ESS depletes my battery in order to feed into the grid.
The system will however go into the recharge state if the soc drops by more than 5% below the minsoc and charge it back up to minsoc, so this will not deplete the battery entirely
I have not found this to be the case. But perhaps I wasn’t brave enough to wait longer.
You can set the maximum discharge power to zero in the ESS menu, that also puts the Multi into this low-discharge state where it only uses a few watts to run its internal electronics.
But if I set it to 0, won’t that disable peak shaving entirely? I do sometimes need peak shaving (or PowerAssist), it’s actually the primary reason for buying a Victron MultiPlus: to sometimes boost the poor power connection that I have in the workshop.
Should I perhaps abandon ESS entirely? Will I be able to achieve my goals in a different way? What I need is two modes of operation: 1) maximize self-consumption (use solar for loads, then to charge battery) with AC disconnected, 2) with AC (genset) connected, power everything from AC with PowerAssist. Battery should only be charged from solar, unless it falls critically low.
Perhaps all you need to do is slightly increase the ESS grid setpoint, so that the battery charges slowly instead of discharging slowly.
Let me give you a bit of background. The Multi consumes some power to run itself, of course. Normally, when it is below the minsoc, we turn the bridge off so that the Multi uses a lot less power. When the battery is below minsoc, you want to use the least power necessary. But when we do this, then no energy can be fed back, and as a result it also cannot peak shave. For many years, that was the only option. Peak shaving could not be done unless the battery was above minsoc. We added this feature later.
On the other hand, if you configure it to shave the peak even below minsoc, then it is going to use a bit more power to keep itself running, because it always has to be ready to shave the peak.
If you set your ESS grid setpoint a little higher, so that instead of slowly discharging the battery it is rather charging it slightly, that should resolve the issues you’re seeing and allow you to keep the peak shaving option enabled. Set it to 100W perhaps, instead of the default 50W.
Hi @iburger not to go too far off topic, but is it possible to disable peak shaving above minsoc? We have a large system consisting of 4x 10k Quattros and do not require peak shaving at all. However, when the we set a scheduled SOC above the minsoc, the system ends up consuming ~500-600W consistently from the DC side (presumably keeping the bridges active). This results in the system having to charge every couple hours from the grid to maintain the scheduled SOC. I see above you mention setting inverter power to 0, though this is a DESS system so may need to invert depending on what is planned. This consumption does not occur once the system is at the minsoc (when presumably the bridges are turned off).
I might not have explained it clearly enough, but in the specific case I’m describing the problem is not with MultiPlus’ power consumption. I know my base power consumption for this entire installation to be around 95W. If I set the grid setpoint to 100W, the problem still exists — the small 100W load every 20-30s or so will cause the Multi to deplete the battery.
I can set the grid setpoint to 250W, in which case it will stop depleting the battery, but I have to manually select the gridpoint appropriately for the specific load pattern, which seems ridiculous. I can’t always know what the load pattern will be the next day.
Thank you very much for answering, but my questions from the previous post still stand: perhaps ESS is not the right solution for this use case at all. I thought it did everything I needed and I thought I could disable the things I do not need (feeding back to the grid), but the regulation leaves much to be desired. Perhaps I should set things up differently?
Hmm. I do not understand why feeding back is required for peak shaving. All I want is PowerAssist: use the battery to help boost grid input if necessary. I do not ever want to feed back. And in fact before I installed ESS, that’s the way PowerAssist worked: no feeding back.
ESS is for systems where you want to work together with the grid. That would typically be where you have solar power installed, and you want to use your solar power for loads, but if there isn’t enough, you want to use the grid.
The other use case for ESS, is people who buy power from the grid when it is cheap, and sell it back later (energy arbitrage).
If you aren’t one of those, then ESS might indeed not be the right answer.
What you are describing, in this case, is that the ESS control loop isn’t symmetrical for your loads. It takes just long enough to adjust the setpoint that more energy comes out of the battery than goes back in. This is why there is a recharge state built in that kicks in if the battery drops by more than 5%, to make up for self-consumption, peak shaving, and this asymmetry. It is not perfect, but it is what it is for now.
If you frequently find yourself taking the battery very low in order to shave peaks, it might also be an indication that you need more battery capacity.
Is there another solution that I can use in my case?
I want solar priority with grid fallback, but I do need PowerAssist: I sometimes need to switch to a “in the workshop” mode where I have to boost my measly grid connection. I have a 5kWh battery, and it should be quite enough for peak shaving, as my peaks are short (single kilowatts, on the order of minutes).
Basically, what I want is ESS, but without any grid feed-in. And ESS sounded nearly perfect from the documentation. What I did not realize is that the regulation is so atrociously slow — which means that in practical scenarios it is quite wasteful, can deplete the battery (it seems), and will feed back significant amounts of energy to the grid when using certain loads.
Hmm. No other suggestions, I guess. In that case ESS it will have to be…
After a couple of weeks I can report that the pathological behavior happens only when peak shaving is enabled. So for now the workaround is to disconnect from AC whenever possible, enable AC only when approaching the minimum SOC, and disable peak shaving below minimum SOC.
But that leaves me with no PowerAssist, which was the main reason why I bought Victron gear.
