MultiPlus-II - some very important questions for me

Question

question

Vladymyr M asked Aug 24, '22

MultiPlus-II - some very important questions for me

Good afternoon.

I want to update my apartment's backup power system, so for example, I want to use my own batteries that I already have and not buy.

Here are a few questions that I could not find answers to in the manual and other resources:

1) I have two electricity tariffs and would like to be able to prioritize charging and full grid operation between 11 pm and 7 am. And in the afternoon or in the evening, be able to gradually "mix" the city network with energy from batteries. Is it possible? Let's say that from 7 am to 11 pm the energy of the batteries will be supplied in the amount of 15% of the consumed load, i.e. joint work of the utility network and batteries?

2) I have LiFePo4 batteries, I have 2 sets of 24v 150A batteries i.e. I can collect either 48v 150A or 24v 300A. But my batteries are with an autonomous controller and their charge voltage is 29.6v.

I know that your company does not welcome the use of third-party batteries, but I already have them, bought them assembled and they still have a lot of warranty.

Actually the question

2.1) Will your MultiPlus-II calculate their residual capacity or will the shutdown and transfer to mains operation be implemented only by voltage? In some resources, I saw that they write that your device, if you specify the full volume of the battery, it will itself arithmetic consider the remaining%(SoC). Or do I need to buy a shunt to work correctly?

2.2) If you program your MultiPlus-II by voltage, can you specify the voltage of the transition to the utility network with an accuracy of 0.1V or only with an accuracy of an integer volt value? (The same applies to the voltage of full and floating charge)

Batteries charge up to 29.6 volts and shut down completely at 25,5 volts. In this case, the voltage may drop even lower, but as soon as the load decreases, the voltage will increase and it will be so until they completely use up their charge. In fact, I have more than 7kW of energy and I would very much like to be able to charge at night, replenish with solar energy during the day (there are no solar panels yet - I’m just planning a system, but there won’t be many of them, literally 2-4 panels), but I understand that to completely abandon the city utility network 230v I can’t, so I really want to be able to use the city network and batteries exclusively during the day, and charge them at night.

But I don’t want to discharge the battery by more than 50%, so I need smart and correct coordination of my batteries with the inverter.

Sorry for writing in such detail, thanks and waiting for an answer.

Multiplus-II

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Jason - UK answered · Aug 25, 2022 at 06:18 PM

@Vladymyr M in short, yes to all 4 points raised. You'll need a GX device to allow this to work and you'll need to set up ESS using the VE config software. You can download the EV config software and run a test version of the software to see what options are available. I'm in the UK and I have a peak electric tariff and a off-peak so similar to what you describe. THe below screen shots of VE config are a test run and not of my actual system.

Once you have set up the config file in EV config, you then set the charge times in the Remote Console (via bluetooth, remote access or via USB device).

1661451280718.png (177.4 KiB)

1661451328358.png (165.5 KiB)

1661451349289.png (140.9 KiB)

1661451446194.png (74.8 KiB)

1661451478907.png (62.9 KiB)

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

mondeoman answered · Aug 25, 2022 at 07:22 PM

ESS is NOT compatible with PowerAssist. Either one or the other.

ESS is a complete solution to your requirements.

PowerAssist could maybe also work, but Scheduled Charging would be more difficult to set up...

1. Yes, but you need the ESS Assistant installed for Scheduled Charging. And for that you need a GX Device. If you will have some loads on the grid in front of the inverter, then you also need a grid meter or an external current transformer. If your loads do not exceed the capacity of the internal transfer switch, then you can connect them to AC Out 1 (critical loads) and AC Out 2 (non-critical loads) and then all the measurements will be done by the MultiPlus internal current sensor.

It's not possible to specify a percentage of power to be taken from the grid. But you can specify a minimum power amount in Watt (Grid Set Point) and the inverter will provide the rest. Many people have Grid Set Point set to 50W. E.g. if you have 500W loads, the inverter will supply 450W from the batteries.

2.1 The MultiPlus can track correctly the remaining energy in the battery, but this works if the inverter is the only load / charger on the battery.

It would be better to have a BMV712 Battery Monitor because it's easier to read and it can also account for other DC loads or chargers.

The minimum battery level (e.g. discharge up to 50%) can be specified in the ESS Configuration as an exact percentage.

2.2 Not recommended to look at voltage for LiFePo4 capacity estimation. See 2.1

PS: 29.6V is waaay too much for LiFePo4...it would be 3.7V / cell. Perhaps this is the "protection" voltage where the BMS cuts off charging as a safety...My suggestion is 27.9V

The shutdown at 25.5V is also very strange...what is the make and model of the batteries, if you don't mind?

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Modifications Space

Node Red Space

Answer 1 · 2022-08-25T18:47:32Z

Vladymyr M answered · Aug 25, 2022 at 06:47 PM

Thank you very much for your response.

Judging from the logic that you have shown, as I understand it, you propose to set a limit of 16A for the input, and then use PowerAssist with a coefficient of 2.0 (I did not understand how much).

Will this allow "mixing" the energy of the battery into the public electricity network?

Where can I read more about this? What does boost factor - 2.0 mean - how much will this% add to the battery?

As for charging by time, it’s clear that many people have this function, and here it looks normal.

Well, about the correct determination of the battery capacity, and not by voltage - probably you need to put a shunt?

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 2 · 2022-08-25T18:58:23Z

Vladymyr M answered · Aug 25, 2022 at 06:58 PM

PowerAssist - As far as I understand it does not suit me? After all, it is only for the auxiliary, i.e. generator, and if I set a small input current to the entire utility network, then it will be charged with a slow current.

https://www.victronenergy.com/upload/documents/Technical-Information-Achieving-the-impossible-EN.pdf (I would like to use the input limit, and by time, that is, during the day, the limit is 10A, and at night when the batteries are charging 25A = Can this be done programmatically? = During the day 10A, and at night 25A)

I want to "mix" in, say, a set % ratio, without limiting the input current parameters.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 3 · 2022-08-26T01:30:52Z

Thank you very much for your replies.

https://logicpower.ua/product/19346 - LiFePo4 24v 150A (I have 2 of these.)

8*3.65v=29.2v and 8*3.2v=25.6v ;)

Sorry, I'm from Ukraine (link to the manufacturer), and in connection with the war, there was a need for a backup power source with the most flexible configuration system.

I ran the tests and charging turns off at 29.2v - or if 2 in series then 58.4v. (This is how it is charged with a proprietary charger)

Full discharge i.e. when the BMS is turned off, about 51v i.e. about 25.5v and at the same time the battery gives off all its power. (BMS protection works and turns off the load to save the batteries)

There are a few more questions:

1) Please tell me, is there a "mixing" of battery energy on both load terminals in the city power supply network? Those. and AC1 and AC2? or only on AC1, which works when there is a city power outage?

2) The ESS algorithm is the same and configured, as I understand it, the same, regardless of whether there is a solar field or not? Even if there is no proprietary solar controller, there will be an "admixture" of battery energy - right? So, if everything goes well, then I can then buy solar panels and a solar controller even from another manufacturer (as I understand it, it’s better to take a branded one, a theoretical question)?

3) Please tell me, if the power of consumers is greater than the power of the inverter, but at the same time there is a city power supply network - is overload permissible? Or does the circuit breaker trip and everything turns off?

The fact is that I want to take the 3000 model (powerful backup consumption is usually 500W-2kW, but there are starting currents of 2 large refrigerators and a pair of air conditioners, and now a 2kW UPS is used for these needs) - I rarely turn on the 2kW electric grill in the kitchen and therefore it must be connected to AC2 - it is not used without city power supply - all consumers would like to be able to be saturated with solar energy (this is an electric grill and a microwave oven and others)

Or will I have to take 5000?

Answer 4 · 2022-08-26T13:01:26Z

mondeoman answered · Aug 26, 2022 at 01:01 PM

You shouldn't charge your battery until it disconnects. The fact that it disconnects indicates that it's trying to protect itself, you are crossing the limit. Even Victron LiFePo4 batteries charge to 3.55V.

Also, at 3.2V there is still lots of energy left in a LiFePo4. I looked at the battery specifications with Google Translate and it says "Minimum Voltage 20V" ... that makes more sense.

MultiPlus-II 3Kva can transfer up to 32A (7.4 kW) from AC IN to AC OUT 1 + AC OUT 2.

When the grid is available, the inverter injects up to 2.4 kW of power into the network so that loads connected at AC OUT 1 and AC OUT 2 use this power instead of the grid. If the loads exceed 2.4 kW, the inverter runs at max power and the rest comes from the grid.

When the grid is not available, then AC OUT 1 receives power from the batteries, up to 2.4 kW
AC OUT 2 is without power.

So you should split your loads into two categories

Critical Loads - up to 2 kW - connect at AC OUT 1
Non-Critical Loads - connect at AC OUT 2
Critical + Non-Critical loads should be max. 32A (7.4 kW)

It would work with other solar chargers, but if you get a Victron SmartSolar, then you will also get integrated control and monitoring into the GX device.

Please see here for more information:
https://www.victronenergy.com/media/pg/Energy_Storage_System/en/index-en.html

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 5 · 2022-08-27T12:11:59Z

ludo answered · Aug 27, 2022 at 12:11 PM

Hi, I would go to an old school solution, use a standard relay as grid supply to the multiplus, turn the relais on over a clockwork in the night , with an override on low soc.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 6 · 2022-08-30T15:13:13Z

Vladymyr M answered · Aug 30, 2022 at 03:13 PM

First of all, thank you very much for your replies.

I can switch the wifi relay, but this type of automation can also be on cheaper equipment, when buying Victron I want a fully automated and correctly working complex.

1) Please tell me what voltage range can be specified for the transition from batteries to the city network?

Interested not in SoC namely in voltage.

Is it possible to specify the transition to 51-53v? and a gradation of 0.1v?

(Many inverters do not allow you to set the transition to work from the city network when the battery voltage is above 48 or the maximum that I have seen with Voltronic 51v-and a multiple of 1 volt i.e. 51 and then immediately 50)

2) In what range can a floating charge be set? those. maintenance voltage?

3

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

mondeoman commented · Aug 31, 2022 at 06:48 AM

Voltage transitions do not work with LiFePo4.

0 ·

Vladymyr M mondeoman commented · Aug 31, 2022 at 10:27 AM

Thank you. But since I do not have a BMS without the ability to connect to it, I will probably need to use the mode for AGM batteries. It was in this mode that I tried and work with other inverters - by voltage.

0 ·

mondeoman Vladymyr M commented · Sep 02, 2022 at 12:51 PM

You don't have to use AGM mode if you don't have access to the BMS.

To see the State of Charge and to make automations based on SOC, just get a Victron BMV712 battery monitor and configure it correctly.

0 ·

Answer 7 · 2022-08-31T18:27:28Z

Vladymyr M answered · Aug 31, 2022 at 06:27 PM

1) Please tell me MK3-USB is not included in the package?

If I buy a MultiPlus-II 48/3000/35-32 GX, do I still need to buy the MK3-USB separately, or do I no longer need a USB adapter thanks to the GX?

2) A 24 volt inverter is more expensive than a 48 volt one. Please tell me if there are any advantages in buying 24 volts?

I understand that the current when working at 24 volts is 2 times more and, accordingly, the load on the inverter, but I also want to understand if there are any advantages in the future? Maybe a 24 volt solar controller will cost less or is it easier to implement something on it?

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 8 · 2022-08-31T22:48:41Z

sharpener answered · Aug 31, 2022 at 10:48 PM

Hi @Vladymyr M.

24V inverter is more expensive because of the higher currents involved. Most people (me included) would go for a 48V system at the power level you are using, I can't think of any obvious reason to prefer 24V

If you cannot achieve exactly what you want with ESS then it is possible to install the Large operating system on a GX inverter and then program Node Red to do the more complicated things you mention.

The MK3-USB is not strictly necessary as you can load all the settings using Remote Access over the internet.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Answer 9 · 2022-09-02T23:06:06Z

zl2fae answered · Sep 02, 2022 at 11:06 PM

I have done this with Node-Red. Works a treat.

2 |3000

Attachments: Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

question