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MihaiR avatar image

Limiting charging current to 0 in DVCC applies to MPPT also?

Hi guys,


Do you know if MPPT is under full control of DVCC settings or my system misbehave?

I have disabled charger but this doesn't apply to MPPT and I have no clue why ...

All components are upgraded at the latest software version (BlueSolar 1.37, Multi 431, ESS 016F)


Thanks,

Mihai


@mvader (Victron Energy Staff)

MPPT - Solar Charge ControllerDVCC
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Hi, you wrote: "I have disabled charger ". What do you mean by that?


MihaiR avatar image MihaiR mvader (Victron Energy) ♦♦ ·

A picture is worth a thousand words:

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MihaiR avatar image
MihaiR answered ·

Hi,


I don't know what exactly the latest MPPT online firmware update did but it actually solved my problem. Looking for track changes on Victron Professional didn't give me any clue but I am more than grateful for solving this issue


Regards,

Mihai


@mvader (Victron Energy Staff)

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mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi; why would you set the Max charge current that low? I don't understand why the system would need to cope with that properly.


In case a BMS wants to stop charging the (lithium) battery; because its full, then the charge voltage will be decreased. Not the charge current. At least: we make sure in our code that a DCL=0 message from the battery is translated into a lower max charge voltage.


Matthijs

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Hi Matthijs,


It was a test in order to understand how the system works, if it is in normal parameters and he's limitations.

Thanks for clarifying that the system is voltage and NOT current controlled but this rise another question and I would be grateful if you can answer:

How actually CANbus BMS stop or slow the charging? REC BMS sends both low charge voltage and current ...


Thanks,

Mihai



More than that, at the end of charging and when the battery is almost full, the BMS send only low charge current to the system. How the system cope with that?

Apparently it works with the rec bms: I heard no complaints.


For the other brands of Batteries and BMS/es it is as I explained above.

MihaiR avatar image MihaiR mvader (Victron Energy) ♦♦ ·

No, does not work in the MPPT case.

Multi is able to decrease the current as requested by the REC-BMS but the MPPT still pump all the available current into the battery, if there is no other loads.

I am lucky because I have a huge battery and just 900W peak PV power on the DC bus. Usually the battery is almost fully charged at the end of the day and the MPPT pumps negligible current into battery compared with what BMS asks.

On the other hand, there was many summer days with very clear sky when the battery was almost full at noon. In this case, when BMS start balancing and asks to the system to decrease the current to very low values (around 2..3A) the MPPT charger didn't comply and still pumps into the battery huge amount of current compared with what is requested.

ok; strange. There is not much we can do about it I'm afraid. It would require looking into; and just limiting the current will lead to issues: you do want the MPPT to output the current required by the AC loads; so just limiting the MPPT is not enough.


The best solution (from our point of view ;-) ) is to make the REC BMS reduce voltage when balancing.

MihaiR avatar image MihaiR mvader (Victron Energy) ♦♦ ·

So izak is wrong seing:

''

Izak (Victron Energy Staff) answered · Dec 06 at 6:26 PM

Yes, the charge current limit set on the CCGX also applies to the solar chargers, but it compensates for loads, so it will attempt to set the solar chargers to about the same value as the amount the Multi is drawing from the batteries to power loads. Additionally, the limits on the solar chargers are adjusted quite slowly, so it is entirely possible that as your loads vary, the solar chargers might take a while before they are adjusted to zero.

In other words, the current limit is approximate.

What you should do is look at the values under the Networked Operation section of the solar charger entry on the CCGX, that should show you how the solar chargers are adjusted.''

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MihaiR avatar image
MihaiR answered ·

Hi guys,


Today I did another test in order to confirm if DVCC - Limit Charge Current setting apply to MPPT charger as follows:

- Battery at 60% SOC and charging.

- No other loads on AC and DC sides

- Plenty of sun on the PV generators, 3200W on Solarmax AC coupled, 710W on BlueSolar

- I have set DVCC - Limit Charge Current to 1A

Results:

1. All the AC power has been injected into the grid

2. All the DC power goes to the battery


Questios:

1. Is this normal behavior?

2. Why MPPT didn't comply to DVCC settings and still charged the battery with 12Amps ?


All the voltages reported by Multi, CAN-BUS BMS and MPPT are the same, hence DVCC is working.

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Izak (Victron Energy Staff) avatar image
Izak (Victron Energy Staff) answered ·

Yes, the charge current limit set on the CCGX also applies to the solar chargers, but it compensates for loads, so it will attempt to set the solar chargers to about the same value as the amount the Multi is drawing from the batteries to power loads. Additionally, the limits on the solar chargers are adjusted quite slowly, so it is entirely possible that as your loads vary, the solar chargers might take a while before they are adjusted to zero.

In other words, the current limit is approximate.

What you should do is look at the values under the Networked Operation section of the solar charger entry on the CCGX, that should show you how the solar chargers are adjusted.

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