I am testing Dynamic ESS and I was playing with Maximum import power in order to set a limit in my grid so I keep to the minimum the capacity tariff imposed in Belgium. During my test I noticed that at least during battery balancing cycle, the systems ignores the current AC Loads and just account for PV generation and Maximum import power in order to charge the battery to 100%, so in my case I had at that time more than 2Kw in AC loads, 1Kw in PV generation and system was loading the battery at 3.4kw= to my setup of 2.4kw for Maximum import power and 1Kw in PV but grid import was in total 4.4Kw.
Could this be double checked and corrected? In meantime I am implementing a node-red to perform the battery balancing cycle and disable it on the DynamicESS.
Another 2 notes:
seems forecast energy consumption didnât account for winter hour change (probably same for summer), probably good to adjust?
it will be nice to account for the battery efficiency, as that could make also some difference from the economical point of view as in a realistic environment total efficiency will be between 80-85%.
I second that. I have to pay a premium for each kW that I use from the grid based of 15 Minute averages. Thus, I set the maximum import power to 2 kW and Dynamic ESS just tried to pull 10 kW from the grid to charge the battery during the cheapest hour of the day.
Ideally, it would spread pulling 2 kW to the 5 cheapest hours of the day.
Maybe I am missing something but I never had any issues limiting grid power. In our DESS setup right up to 35A rating of our main fuse / smeltzekering, plus 10%, just because (smelt is specified not to blow upto 140% I-rated). During charging an additional HF chargebank(on AC-out2) draws 8kW ~ 230Vac 35A, fluctuating a little with main Voktage. The MP-II adds another 0.5kW chargepower, upping the current to about ~38A (with settings at 40A (not 36A shown below), somehow the MP keeps a 5% safetymargin, donât know why.
The interesting part is that the MP-II will effortlessly, instantly and reliably keep that 38A flat, even when starting heavy duty loads, all the way up to what it can deliver, which is over 4 kW (inverting, not charging) plus the 0.5kW âheadroomâ on the mains fuse, up to 5kW total.
I never tried the limits but I bet you a beer the MP-II will simply shut down when it detects a persistent overload over the 38/40Ă limit as set via VRM.
If using a separate grid meter or the remote currentcoil directly at the incoming mains, right after the utility meter, it doesnât even matter where those loads are connected w.r.t. the MP-II but I chose to put the 8kW chargebank at AC-out2 because out-2 can be disconnected with the relay in the MP-II. I fully expect the MP-II (battery and settings permitting) to absorb upto 3.5kW if surplus solar as well, it simply regulates its charge/invert power to maintain that 38A Vac (during a charge cycle of course).
Sorry, I am missing the point you are making. But I appreciate the insights. I have since upgraded all the firmware and can finally now set the max. import current in a peak shaving submenu. This is honored, as I have tested it with âkeep batteries chargedâ and now the max current per phase is pulled, if there is more demand, the battery supplies the rest. This is how I would have liked DESS to act on its own. Maybe I can give DESS another shot with that enabled.
yes, this is set to the fuse limit, which is 35A for me (I am more conservative). However, I would really only ever take 4 kW from the grid, as I have to pay extra for more power. Which, of course, means I could set it to something like 7A. But I do not want this to be a hard limit such that my house has to shut down if demand exceeds this. I want 4 kW to be the max. âunder normal circumstancesâ
Is that the system has protections in layers. On the grid side the MP-II is certified to provide the âlast ditchâ protection of your mains fuse / power limits, either by regulating charging/inverting power to ensure the maximum grid current will go up to but not exceed the set 38A OR by shutting down if it canât (overload condition). I suspect you were trying to achieve a sortlike limitation, albeit further down the line in the ESS or DESS settings.
but I do not want this to be a hard limit, if the load is there, by all means, the necessary power should come from the grid. BUT, it should not pull up to 35A from the grid to charge my battery. I want charging the battery to be limited to 4 kW from the grid (solar as much as the battery can take).
Well thatâs a whole different problem altogether, best solved by adding battery capacity. Or programming your own Node-RED flow to manually/dynamically adjust the grid power limit. But you wonât find a standard function for such an, arguably, edge case use case.
Since yesterday, I own a 100 kWh battery - YAY - up from 40. Letâs see how much this helps. Cannot really add more because of building code regulations
That setting belongs to the MP-II so either use victronconnect with mk3-usd or Bluetooth or through the Cerbo GX with VenusOS large, then there is a standard Victron node available to set that limit _on the MP-II _ with.
You still need to dial down that max grid Amperage first and then define the âexceptionsâ and a means to automate those, or stick with occasional manual adjustments. The âdialâ is right there on both VRM as well as the app (top left). Thatâs for a reason I suppose.
Is it? Your DESS questions are valid but you need to study more, especially the limitations that DESS comes with, such as disabled having peakshaving and scheduled charging/SoC IIRC. Some ESS functions simply donât combine with DESS (from a systems engineering perspective disabling those functions is correct).
Limit AC grid current
Limit DC MP-II charge current
Define exceptions and try Node-RED to make a simple automation, even if only for adding alarms and virtual switches to (temporarily) manually change above mentioned limits.
None of those fancy ESS functions will achieve what you want (when running DESS) and that is by design. Iâm pretty sure Victron has documented those limitations, somewhere deeply hidden on the interwebs.
