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.