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Marius Marais avatar image
Marius Marais asked

Limit grid battery charge current when AC-coupled

So, this has been asked before: https://community.victronenergy.com/questions/91604/limit-battery-charge-current-from-grid.html

But I'm piling on with a related problem: In Cape Town, grid-tied hybrid (i.e.ESS-like systems) are not allowed to charge the batteries from the grid by more than 25% of the main breaker capacity.

So, for a 60A breaker, I need to limit the grid usage for battery charging to 15A. I know I can limit the charge current and it will work fine when combined with DC-coupled MPPTs which can charge the battery directly with no limit.

However, in my case I have an AC-coupled Fronius on the output of the Multi, so I want the Multi to charge at full capacity when using solar, and 15A when those amps are coming from the grid. It does not seem possible to limit "grid amps for battery charging" in that configuration. Everything limits the entire charging process or the entire pass-through current, even from solar.

Any way to achieve this?

(In ESS, charging from the grid is rare, but when it happens I need it to be limited to 15A to comply with regulations, without harming overall system performance.)

Multiplus-IIESS
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Marius Marais avatar image Marius Marais commented ·

Would this work? It says AC-In, does that specifically mean PV inverters on AC-Out are not affected?

https://www.victronenergy.com/media/pg/Energy_Storage_System/en/configuration.html#UUID-5de4e316-c4ad-8a50-dc36-7e78fb8a9908

4.3.9. Limit charge power

This setting limits the amount of AC power used by the Multi for battery charging. The limit also applies to AC power received by the Multi from any grid-tie PV Inverters connected to AC-in.

In other words, this setting limits the flow of power from AC to DC on utilities connected to AC-in.

  • This setting does not reduce the charge power coming from MPPT Solar Chargers.

  • This setting only applies to utilities connected to AC-in: In inverter mode, the 'charge-current setting' - as configured in VEConfigure - is used to control power coming from grid-tie PV Inverters.


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bbmz avatar image bbmz Marius Marais commented ·
This should work - see detailed answer below
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Marius Marais avatar image Marius Marais bbmz commented ·
Nope, see below.
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marekp avatar image marekp commented ·
@Marius Marais

I am just curious, how your grid supplier is measuring how much of the power from grid is used by you for charging and how much for other house loads?

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Marius Marais avatar image Marius Marais marekp commented ·

It's part of the legal registration process for PV and UPS systems. Technically it would be very difficult for them to do.

But ZA already has load-shedding problems, how much worse would it be if everyone immediately recharged their batteries at full breaker capacity once the power came back on?

I don't really care if my batteries recharge in 20m or 4h, as long as they charge. I would like to comply with my local legislation without impacting my ability to charge from PV.

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nickdb avatar image nickdb ♦♦ Marius Marais commented ·

Considering an ESS should be capable of running well longer than 2 hours without going to grid to charge, it would seem the simplest answer is to size the battery sufficiently large enough that this isn't an issue. Fortunately not a reg that affects any other province in ZA. Every conventional household has geysers, non-smart battery backup and high power appliances kicking in regardless at scale, so it's a bit of silly, unenforceable bureaucracy.

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Marius Marais avatar image Marius Marais nickdb ♦♦ commented ·
Sure, I'm not about to rip the system out, but if there were a setting I could turn on, it would be automatically compliant without handwaving or charge current control switches and so-on.

Also, life would be so much easier if everyone could just decide, personally, which (by-)laws they follow... :)

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marekp avatar image marekp Marius Marais commented ·

@Marius Marais

If I understand you correctly, the grid provider has no way of knowing for what load you are using energy from grid.

So the limits for charging battery are only on paper (regulations).

I do not know how cold are winters in your country, but in mine when grid fails in winter the house is getting colder and colder so when power comes back first power goes for heating and for battery charging if battery is present.

As for limiting charging current from grid, it is not easy with one MP-II.

If you start limiting charging in DVCC the limit will also apply to PV inverter.

You could install a separate small charger with limit that you are allowed to have and your main MP-II set only for inverting. Problem here is with PV-inverter that will not be used for charging at all.

All depends on how efficient is your grid supplier in chasing users going over the charge limit.


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4 Answers
kevgermany avatar image
kevgermany answered ·

It's your mains in. Was going to mebtion it, but not sure about ESS.

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Marius Marais avatar image Marius Marais commented ·

Yeah, seems like I would need to actively test it out.

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roland-trautner answered ·

Hi, I have a similar issue - I would like to limit the battery charging power from AC-in (=mains) to prevent the cooling fan of my MultiPlusII starting to run in the night (it is pretty noisy) - but I am afraid my CCGX (with latest firmware, 2.73) does not show the option of "limit charge power" described above / in 4.3.9. Any help would be much appreciated. Thanks !

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dipster25 avatar image dipster25 commented ·

@Roland Trautner did you ever get a solution to your issue ? I also have the same cooling fan issue with my Quattro 48/8000 when charging the batteries from the grid ay night. Mine is a new installation and I also do not have the 'Limit charge power' option available. Thanks in advance

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bbmz avatar image
bbmz answered ·

The victron manual is very explicit here. You have to connect your PV inverter on the AC out side of your multiplus to give the ESS a chance to differenciate between grid charging and „(AC) PV charging“.

But be aware: this change in cabling need quite a few changes in settings, too.

Are you allowed to feed-in excess power? If yes, you have to make sure, that the multiplus will do that (if batteries are full). In case of grid-failure or forbidden energy export, make sure your Victron System can limit the power production of the fronius (e.g. via frequency shift in grid-failure situations or Modbus TCP otherwise).

Also make sure that your Fronius hasn‘t higher wattage than your victron‘s or batteries‘ charging capabilities (factor 1.0 rule).

And finally - if your Fronius is a multi-phase inverter - you might need a multi-phase Victron system, too.

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Marius Marais avatar image Marius Marais commented ·
This does not work. MultiPlus-II 48/10kVA + Fronius Primo 5.0-1. Fronius is set to MG50 + Modbus control, ESS is working 100% when grid connected.


DVCC "Limit charge current" setting limits charging from the Fronius on AC-out while the grid is disconnected (I've not checked while grid is connected). The control isn't very fine, so output frequency spikes and Fronius turns off.

Turning that setting off keeps the Fronius running during grid failure to charge the battery.

So there doesn't seem to be any setting that just applies to AC-in.

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roland-trautner avatar image
roland-trautner answered ·

Hi, thanks bbmz for the quick answer. My PV inverter is already connected on the AC out side, and I am allowed to export excess energy into the mains network. I have a single phase MultiplusII and a 9.6 kWh battery. On sunny days the battery remains full and I am exporting energy; but in winter the battery sometimes runs low and I would like to top it up in the night (when electricity is cheaper and excess green energy is available from wind power in my area) with a moderate input current so I do not trigger the noisy fan of the charger in the Multiplus.

As stated the CCGX shows no ESS option "limit charge power". The only option I found is in the Multiplus settings where I can limit the mains current to the Multiplus (now set to 16 Amps). I could reduce that (for example to 2-3 Amps) but then I am afraid that when the battery is full and the PV inverter delivers 2000W on a sunny day the Multiplus would limit that too, and power down or off the PV inverter ... which is not what I want (unless the current limit in the MultiPlus configuration is only for supply current, not for exported current ?? but I do not think so as this is supposed to protect the mains line / fuse ...)

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Marius Marais avatar image Marius Marais commented ·

@Roland Trautner The setting you're looking for is under DVCC, Charge current limit. It may only be visible in installer mode.

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