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craig avatar image
craig asked

Multiplus 2 mains input and generator

I have a customer with an older 3kw Grid connect solar system. We want to connect a Multiplus 2 with a lithium battery as a piggyback on the mains AC buss with an energy meter (multiplus intput on mains buss). The output of the multiplus we want to connect to essential house services. Any excess solar that would normally be exported will be used to charge the battery and run essential services, the grid will not be used to charge the battery. When the grid is down for extended periods the customer wants to be able to connect a generator to the multiplus input to run essentials and charge the battery. My question is, with minimal user intervention, how can I tell the multigrid it is ok to charge from the generator? it doesn't know if it's connected to the grid or a generator, it's not allowed to charge from the grid, but is from a generator? All I can find is the charge current control assistant, but I think this will interfere with the excess solar charge.

MultiPlus Quattro Inverter ChargerchargerGenerator
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Paul B avatar image Paul B commented ·

The correct solution is to have a Quattro unit

however there is a few ways to do this I THINK but you would need to get a victron distributor involved in your area

ie you could install a CCGX unit and then activate the Generator autostart feature that would activate on a mains failure trigger, you would have to manually turn this off as there is no way to know when the grid comes back on, (it may even be possible to have a sensor on the mains to turn off as well MAYBE that is)

this would then control TWO contractors that connect the generator to AC1 and disconnect the Grid, after a set period of time ie 10 min or however long you want to wait.

Now the system would know that the generator is connected

you would then have to program an assistant or a ess system to control the charging when on generator.

NOTE I have not done this sort of thing myself but I believe this could work for you. with some mucking around and thus be close to automatic.


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Ben Stanton avatar image Ben Stanton commented ·

Hi Craig, How did you get on with this setup? We have a customer wanting the same solution and I believe it will be getting more and more popular... Very keen to know how you got on.

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1 Answer
popnic avatar image
popnic answered ·

@Craig I have this setup. Multiplus II and Cerbo GX, grid and manual starting generator. The difference is that I am not allowed to fed the surplus to the grid yet.

First, Multiplus 2 having one AC input and does not know if a generator or grid is connected to it. But you can tell to Cerbo if a grid or generator is connected to AC-in 1 and this will change the behavior of the system.

I put some numbers to the sentences below because I want to refer to them later.

1. I set in MP2 ESS assistant using VeConfig. For this you have to choose your Grid settings and use 60 seconds for reconnect time for testing purpose. Note that if you set a grid code you need a password to change it again but being a installer you konw more than I do about grid settings and LOM. If your generator output not fit to your grid settings, Multiplus will reject the generator.

2. In Cerbo Remote Console > Device list, in Multiplus device you can set Input current limit ie. 10A This will be the max current that will be use by Multiplus to feed the load and charge the battery.

3. Cerbo Remote Console > Setting > ESS > Set parameters for ESS :Minumum SOC, Limit Charge Power, Grid setpoint etc. In my final installation if I choose to use ESS then i have to install antiislanding device.

Generator: Cerbo Remote Console > Settings > System Setup> AC input 1 to Generator.

The system will work using 2, will ignore SOC from 3 and it will charge the battery using charge power limit form 3 and fed the load as long the generator is running. If the load power is higher than gen power, the inverter will use power from battery to supplement the gen power.

Grid: Cerbo Remote Console > Settings > System Setup> AC input 1 to Grid

The system will use the limit from 2 but, it will charge battery using charge power limit until SOC condition is fulfilled and it stop the charging. During charging the Grid setpoint is ignored. After that, the load will be feed from grid in the limit set in Grid setpoint and supplemented by inverter from battery.

Both MP and Cerbo has a lot of options and conditions for start/stop the generator but I did not use them. First I will use the stop condition my generator being manual.

Maybe there are other much clever solution to this problem other than Quattro. I am curious how you guys did it or and advice from Victron.





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