I have 2 grid-tied paralleled 5kW Multiplus IIs (MP2) and a ~15kWh battery setup in my home which have been configured, up to now, as a simple mains failure backup (a UPS, if you will). I do not have any PV or a back-up generator.
I would like to have some help in setting up what I hope will be a simple assistant-based way of saving money on buying expensive electricity by using the MP2s to power the house’s main consumer unit all the time outside of Octopus’ 1:30pm and 05:30am cheap rate (I had a Liberty 116 smart meter installed a while back) and thus to prevent my MP2s from both charging at peak electricity rates (unless they are below, say 10% SOC which would be very unusual) AND prevent expensive AC ‘passing-through’ to power the house. Ie I solely want to run the house on the battery outside of the overnight cheap rate (hope that’s clear!).
It is worth mentioning that the hot water heating and garage are on a separate CU (for various reasons) and will be unaffected by all this.
I have a Mk 3 USB dongle. It and the MP2s have just had their respective firmwares updated. I only have a Color Control GX display, nothing else (nor a Cerbo, etc).
I have installed a mains timer switch which controls a simple pair of 0V contacts which I plan to use with the MP2’s ‘Aux 2’ port. Beyond that, I don’t want to muddy the waters with what I think I understand about which assistant I should use, rather, I would like someone to suggest something they know works, please.
Thanks for the reply (and apologies for the delay in replying – for some reason someone objected to a previous post some months ago and my account has been locked ever since - so I tried to reregister but the system was too clever for me and banned that account too! Now resolved…).
As you can see I have edited my original post as I did not fully define my circumstances. Yes installing the ESS assistant will address the issue over when the multiplus will charge but it won’t address the question of preventing mains AC passing through to power the house during expensive peak rates.
So I am back to the question of using the aux port with a timer to stop the AC passing through (as well as stopping charging) during peak rates and I gather that the best assistant to permit this is the ‘Generator start and stop’ assistant.
This YouTube video (youtube.com/watch?v=4ZsGHi8nKGc&t=478s) gets close to it but confuses the issue with the scenario under which the MP2s in the video are being controlled… which is not my scenario. He also has a Cerbo and I do not.
I’m not with you here. The way my MP2 works is that loads are powered by battery first, and only uses grid power for any top-slice above the kVA power of the inverter.
I’ve setup my system with a scheduled charge that starts and ends in off-peak tariff and the battery powers the house using this energy for the rest of the 24 hours.
No clever switches, disconnecting or programming.
My MP2s are set to UPS mode so if they have AC power, it is passed through via the ‘AC Out 1’ relay and the battery is charged. If the mains is not there for whatever reason, then the inverters switch on, taking energy from the battery to supply the house instead of the mains ie it is like a n uninteruptable power supply. The MP manual describes the MP’s function thus: “Automatic and uninterruptible switching. In the event of a supply failure or when the generating set is switched off, the MultiPlus-II will switch over to inverter operation and take over the supply of the connected devices. This is done so quickly that the operation of computers and other electronic devices is not disturbed (Uninterruptible Power Supply or UPS functionality)….”
All of that is true, but what makes you so sure that what I say is not true?
Can’t both be correct? Are you sure that your system works the way you describe?
Outside of the ESS>scheduled charge times, loads are served by the battery (and any connected MPPT solar chargers) until it is discharged down to ESS>minimum SoC. After that, loads are served by the grid until the grid fails, and then loads are again served by the battery until it discharges down to the floor. Then the lights go out.
Perhaps you have ESS>minimum SoC set at a very high % ? I have mine set at 20%.
I am definitely a newby here so I bow (if not positively grovel) to your greater experience knowledge.
The UPS setting I referred to is not in the ESS config menus but under the basic MP configuration (see P19 in the MP manual)… but probs a red herring anyway…
I have changed the ESS mode to ‘Optimised without battery life’ (from ‘Optimised with battery life’). So I now have:
Mode: Optimised (without battery life)
Grid metering: Inverter/charger
Multiphase regulation: Total of all phases
Minimum SOC (unless grid fails): 40%
Limit charge power: On
Maximum charge power: 2400W
Limit inverter power: Off
Grid set point: 10 W
Grid feed in:
-AC-coupled PV - feed in excess: Off
-DC-coupled PV - feed in excess: Off
-Feed-in limiting active: No
Peak shaving:
-Peak shaving: above minimum SOC only
-Limit system AC import current: Off
-Limit system AC export current: Off
Scheduled charge levels: Inactive
-Schedule one: Every day 00:30 to 05:30
I now see a slight export/import current which increases significantly when the AC loads are significant. Eg with AC loads at ~600W the export to the grid is around +/- 50W or so (ie sometimes its exporting sometimes importing) and with the kettle on (~2500W or so), the export goes up to ~200W. Obviously, I would rather not be exporting or importing anything. Can I prevent *any* export? (Suspect this may be down to ‘Grid metering: Inverter/charger’…?)
The inverter has a response time of a second or two when a big load like your kettle comes on or goes off. Loads are continuously variable as the multiple circuits in your house do their combined thing.
non-zero response time is inevitable and during these short periods there will be import or export with the grid as the inverter ramps the battery up or down to match the load. This “wasted” energy is probably not worth worrying about.
But after a couple of seconds when the inverter has settled, the grid current should approximate to the setting you have in ESS>Grid Setpoint. Is this happening for you?
Well, it seems to be working OK. The battery charged over night at the right times (need to increase the current a bit as it didn’t fully charge) and the AC didn’t pass through again outside those times since my last message. I’ll post some shots of the VRM graphs re the back-feeding to the grid thing which is still more than I‘d like but, as I mentioned before, this may be due to the lack of proper external metering than anything. Thanks for your help.
In the meantime, can I assume that I am correct in thinking that the ESS assistant handles the fact that I have 2 x MP2’s in parallel without me needing to do anything to the slave MP2 in the way of changing settings, etc?
Having set the Max Charge Power in the ESS section to 2400W (÷ 48V = 50A), is that between the 2 MP2s or will the batteries actually get 2 x 50A?
At https://www.victronenergy.com/live/assistants:how_to_add_and_configure_an_assistant… it says “Note for three-phase and parallel systems: some Assistants need to be configured in in all Multis or Quattros in the system, others only in the master of L1 or in all phase-masters. Carefully read the instructions in the Assistant pages while configuring.”
However… I have just had to change the ESS assistant on the Master MP2 and see the very first thing the assistant says when one clicks on "‘Start Assistant’ is “This assistant must be placed in all Multis/Quattros of the system.” If so, I don’t understand why this is not mentioned in either of the above two manuals.
If you could connect any amount of PV to your system, you would qualify for Octopus SEG payments. Then you could collect a few pennies for this exported energy.
I have my grid point set to -100Watts which keeps my MP2 exporting at least a very small amount 24/7. It often reads 30 Watts or so export on my IHD. It works out about 0.5kWh/day additional export.
I do this because there’s a cost benefit of NOT importing the same amount at peak rate, whilst collecting a little more SEG.
I do have a ~3.5kWp tracking array, as it happens but it is not MCS certified (if that makes any difference to the SEG thing). But, because that comes into the garage and because the link from garage to house is underground and not very capable, my longer term plan is to have a much bigger battery in the garage, add a small wind turbine (we get lots of wind up here in winter - the turbine up the road averages 8m/s for the middle 4 months of winter) and island it from the house with its own 5kW MP2 to principally charge my EVs and other battery-powered kit. It’s all very ‘experimental’…
I understand that Octopus will accept non-MCS exports if you first pay them a fee for doing some desktop certification of your installation. Drop them a line & ask
I don’t know of any Victron products that directly interface wind turbines to MP2 etc in the way that the mppt chargers do for PV, but I suppose the turbine could be AC coupled on the AC-in port?
I refer to the same document. True, it says some assistants must be loaded onto all inverters. But then it adds “…with all others, a unique configuration can be made in each unit”. The way I and some others read it is that unless the loading of a particular assistant is explicitly prohibited or it’s obvious to anyone that it is irrelevant, then it has to be loaded onto all inverters. See this thread as an example: Parallel MultiplusII GX with MPII using Assistants. - VictronEnergy
Running a parallel system with quattros, my understanding has worked so far. Some people use the demo mode to determine whether an assistant has to be loaded onto all units.
The document you referenced first mentions the ESS assistant as one of those that must be loaded onto all units.
The turbine I have (Istabreeze 2kW ‘Windsafe’) came with its own controller and dump load. So, the plan is to connect it to my battery via a Victron SmartShunt so the Victron system can see what energy the turbine is producing. Ideally, I plan to also have a basic relay to disconnect the turbine controller from the battery if the controller failed in a way that caused the battery to either over-charge or over discharge (perhaps this is either unnecessary or impractical?).
