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john-hagtharp avatar image
john-hagtharp asked

Problem with DVCC charge current limit and parallel multis?

I'm running latest release candidate in my CCGX so posting here in case it's an issue with the beta.

I have 2 x Multiplus 48/3000/35-50 (firmware version 431) in a single phase parallel setup. I'm using the DVCC maximum charge current setting to avoid hitting my smallish battery bank too hard. It worked as expected previously with a single Multi but, now I've switched to the parallel setup, I've found I need to specify half the desired charge current. A setting of 17A gives me 34A charging current.

This seems to be a bug. I have not tested but expect it will be limiting my day time charging from the solar chargers to 17A so running this way is not ideal.

I'm happy to do further testing with different firmware versions if required but will need to run the battery bank down some time to do so. I usually run ESS "keep batteries charged".




MultiPlus Quattro Inverter Chargerbattery chargingDVCC
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2 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Thank you John, we’ll look into that. Is it ok if look up your system on vrm & login on remote support if necessary (pls enable that feature)


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john-hagtharp avatar image john-hagtharp commented ·

Hi Mathijs. Yes, please feel free to login. I just removed the VNC password so I think it's ready for you to connect. Installation 13976.

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john-hagtharp avatar image john-hagtharp commented ·

Thanks Mathijs and Izac. Only two weeks from reporting the issue here to a fix being available. Another good reason to choose Victron!

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Elimac avatar image
Elimac answered ·

Hello,

I have also 2x Multis in parallel and I can't see the same behavior. In my case it seems working as it should, at least in high currents. Tested changing from 40A to 60A and it instantly changed.

However, in lower currents, is not as precise, and normally I have to set lower (for example, set for 10A to have 15A) but is not half in my case...

2x Multiplus 24/3000/70-16.

VenusGX with last beta

2x MPPT 250/60


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Elimac avatar image Elimac commented ·

The Multis have latest version, 459 and the MPPTs have 1.39

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john-hagtharp avatar image john-hagtharp Elimac commented ·

I'll cycle the batteries down and test this again. As I keep the batteries charged, I only had one opportunity to observe this when grid power was restored late one evening. The solar chargers were playing no part.

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Elimac avatar image Elimac john-hagtharp commented ·

That is a big difference from my case. I was charging with 2x MPPTs, Multis were purely inverting. I didn't have the chance to charge with Multis yet, so I will not be surprised if I see the same as you. Keep posting! When I can I will also check with Multis charging.

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john-hagtharp avatar image john-hagtharp Elimac commented ·

I ran the batteries down overnight and did further testing this morning.

The issue seems relatively clear and will only show up in systems where the Multis are charging the batteries. With the panels disconnected and all charging coming from the pair of parallel Multis, The charge current is exactly double the DVCC charge current limit. So a 17A setting gives me 34A charging current.


With panels connected and 10A combined coming from my BlueSolar MPPTs (still only 7am here), I get a total of 24A charging current with that same 17A DVCC setting. I believe that's due to the "VE.Bus device" being instructed to supply the remaining 7A which ends up as 7A from each of the parallel Multis. The total is therefore 10A + 7A + 7A = 24A.


Under the covers, I don't know if Venus on the CCGX is currently aware it's talking to parallel devices but I'm guessing the fix will either be for Venus to reduce the current it instructs to the Multis by dividing by the number of parallel devices or a change in the MultiPlus firmware so the same adjustment is made there.


Or maybe I've just messed up something on my system and there's no work for anyone else to do!

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Elimac avatar image Elimac john-hagtharp commented ·

I believe you may have found something. I have to correct also my post:

When I said:

However, in lower currents, is not as precise, and normally I have to set lower (for example, set for 10A to have 15A)

I remember now it was raining a bit, and to finish the carge for the day, I turned ON the Multi Charger, limited on the ACin, and using some solar at same time. And I noticed the effect. I found it strange, but thought it could be just lack of precision, as the currents were not very high (both solar and from grid).

The charge limit was always overshoot by some margin, and I reckon now it can be the same as what you are observing.

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john-hagtharp avatar image john-hagtharp Elimac commented ·

One more observation and potential bug that may not be related to parallel operation:


I'm up to around 70% SOC now and the sun is starting to work. The VE.Bus device shows "Bulk". The grid appears to be being used exclusively to power the loads. The solar chargers are attempting to cook my batteries. The DVCC charge current limit is having no effect whatsoever. The charge controller states are showing "external control".


Switching ESS to one of the "Optimized" modes does not help.


Disconnecting the grid fixes the problem. The VE.Bus device now shows "Inverting", the battery charge current is being limited to exactly the DVCC charge current setting and the solar chargers appear to be throttled back when required to achieve this.


Charge controllers are running version 1.39.

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john-hagtharp avatar image john-hagtharp Elimac commented ·

I can confirm the DVCC charge limit issue has been fixed in release candidate v2.30~50.

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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ john-hagtharp commented ·

Thanks! Good to close the loop like that.


:thumbsup:

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