question

Assuming correctly configured/connected.

BMS controls the MPPTs and multiplus through the Cerbo.

BMS sets the charge rate, so large arrays will not result in a charge current that is too high for the batteries.

When batteries close to full BMS reduces the charge rate.

When batteries full BMS stops the charging.

Inertia shouldn't be a problem due to the reducing charge rate as the batteries fill.

Do you want to feed in?

As mentioned before, the Pylontech Batteries will shutdown the SmartSolar MPPT but if you want to continue to feed-in the 2,4kW from the MultiPlus-II the configuration of the system become a little bit complex.

I have a customer with a similar situation but with three MultiPlus-II 48/3000, a RS 45/200 fully equipedwith 12kWp solarpanels and 50kW of Pylontech batteries and I was unable to tell the Cerbo GX if the Batteries are at least 95% full to feed-in up to 7kW-3P (authorised)

Hence currently my customer is waising a lot of energy because of the Pylontech batteries which take control over everything. (I hate this type of BMS)

Hence i am interested in a solution too.

Hello Michelle,

Yes I do (want to ) feed in, but not necesserely all.

I have installed more PV power for the "winter" time to fill the battery also in wintertime (will be changed to a off-grid Car charging station later (during summer time)).

It does work since 3 days @not so good weather :-), so I have to handle 2...3kW after batteries have been charged. But I may have to deal with max. 5kW once the weather will be perfect.

Surely all 3 MPPT can be controlled down to zero watts by the CERBO, my concerns are more how fast this will be in order not to harm battery or multiplus. In theory it does work...

BTW, I found on the data sheet the following power figures for my multiplus II 3000 230V 48V:

a.) Maximale offenkundige Einspeiseleistung 3000
b.) Spitzenleistung 5500 W
But I cannot say what they mean, which power rates here are applied.

And if the MPPT can control e.g. 5kW, it should be possible to control even more? And if yes: How much? :-)

Thanks a lot once more

@Imperator69

I have a MP II 3000/48 as well and my total installed panels with 3 MPPTs are 8kWp.
I can't speak for Pylontech, but I am using a Seplos BMS and there was no trouble during summertime. CerboGx switches complete MPPTs off, when the generated power is enought for the system. If the batteries are completely charged, CerboGX throttles the power down, so there is no overpower-issue.

Hope that helps,
Wilm

Hello Wilm,

yes this does help and lets me sleeper better now - definitely :-)

Your setup in your well appreciated answer leads me to a second Question to your setup: For my off-Grid Car charging station I would like to build my own Battery (approx 15kWh). You mentioned a SEPLOS BMS. Is this like here: https://lichtex.de/SEPLOS-CAN-BUS-2_0-BMS-8-16S-LiFePO4-Batterie-Management-System-24V-36V-48V-100A-150A-200A-LFP ?
Do you have an extra balancer? Anything extra?

For the CAN communication with CERBO do you need anything extra (Hardware-/Software protocol etc.)?

Thanks a lot for your help and looking now forward for the next project (I then will change the 3K Multiplus to a 5K multiplus at home and use the old one 3K for the Car charging station...)

Jochen

Hi Jochen,
I have ordered a complete Seplos-Mason 280Ah box from China without cells. Those were obtained from the well known shop in the Nederlands. As the balancer in those, Seplos BMS's is a little bit to small, there is enought space to place a NEEE (Heltec) active balancer in the housing. You need a self wired CAT5-cable, so search for Offgrid-Garage on youtube. Andy has made several good videos for the CAN-Bus-cableing.

Best Wishes,
Liebe Grüße,

Wilm