question

baard avatar image
baard asked

DVCC Maximum charge voltage - not working....

Hi,

In my boat I have the following Victron equipment:

Multiplus 12/1200/50-16
SmartSolar MPPT 100/15
BMV-712 monitor
Cerbo GX

Batteries:
3 x 100amps "oem" Lithium with built in BMS

I have activated DVCC on Cerbo GX because I want to limit charge voltage when boat is at dock connected to grid. Want to have the batteries between 60-80% SOC for better battery life. The problem is that the charger does not seem to limit the charge voltage at all. I have set it at 13.1 volt, but the charger continues to charge above this voltage. There is communication in place because if I set the charge current to 0 the charger stops charging (status remaining in bulk).

So the problem is that setting DVCC Max charge voltage does not take effect in Multiplus, and the charger charges the battery beyond set voltage.

Does anyone have any clue to what might be wrong?

Best regards
Baard Lindberg, Norway

DVCC
9 comments
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13.1v is an unknown SOC.

Andy has plenty of time and tools to test Lifepo4 batteries.

Absorb voltage of 13.8-14v is ok. Float voltage of 13.3-13.4v is ok.

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baard avatar image baard klim8skeptic ·
Hi, What do you mean by unknown SOC? I know float values of 13.3-13.4 is ok, but I would like to keep batteries at lover SOC when connected to shore power over a longer period of time.
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What SOC @13.1v mean for you?
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baard avatar image baard klim8skeptic ·
Well SOC for me is "State of Charge". 100% will mean that the batteries are full, and the batteries voltage will be something like 13.5 volts or more. As the batteries drain the voltage will drop. So as an example when the voltage is at 13.1 or 13.2 the SOC will be at 50-60%. So with limiting the voltage with DVCC the battery will remain at some SOC state that is lower than 100% - I will then turn off the "max charge voltage" or adjust it to target voltage for 100% SOC to fill the batteries up again....Hope that was understandable.....
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Post some screen shots of the multiplus charge settings, DVCC settings, and a description of your BMS.
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@baard@teba.no

>There is communication in place because if I set the charge current to 0 the charger stops charging (status remaining in bulk).<

What makes you so sure there is communication going on between your BMS and the GX device, via which connection?

Setting the charge current to 0 with DVCC on and working with compatible devices (MulitPlus and MPPT) is expected behaviour but no proof that your BMS can communicate with the GX device.

If the BMS is not connected via CAN-bus and if the battery is not supported (see the Battery Compatibility guide), then you should not activate DVCC. If you do it anyway, all kinds of things can happen.

If you're referring to 'Limit managed battery charge voltage' when you said "DVCC Max charged voltage", this feature is intended to be used only for example when the managed batteries are completely out of balance and required to balance at a specific charged voltage.

bildschirmfoto-2022-06-07-um-213016.png


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baard avatar image baard Stefanie ♦♦ ·

Thank you for your answer and clarification! You are right, my batteries BMS do not communicate with the Cerbo - My batteries is OEM lithium with a BMS with no communication possibilities. But I have 1 further question:

Since my battery has its own BMS with no communication with Cerbo. Is it still advisable to use DVCC to limit maximum charge current? The battery compatibility guide suggest it is.

I want to use this function to limit SOC til around 70% when connected to grid for a log time. I will do this by creating a NodeRed or HomeAssistant automation that turns the limit maximum charge curren to 0 at certain SOC percentages.

Regards Baard

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1. Yes and no. If you want to have full DVCC capability (BMS controls DVCC capable devices/chargers via GX), then the BMS needs to communicate with the GX device. Without, it's only a "slimmed down" (is that English?) version of DVCC - you can limit charge current and get SVS, STS and SCS.


2. You can leave it on, just in case you need to limit charge current. But bear in mind that this only works with DVCC compatible devices like the MultiPlus and MPPTs.


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baard avatar image baard Stefanie ♦♦ ·

Thx again - edited my previous answer after carefully reading about DVCC. I understand I will need communication with BMS, but that is not possible with my current batteries.


So I will set DVCC in accordance with battery compatibility list and enable limit charge current, SVS and STS. I have one MultiPlus and one MPPT on board.

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2 Answers
nickdb avatar image
nickdb answered ·

Keeping batteries at that state of charge isn't going to help their useful life, if anything it will make it more difficult for cells to remain balanced. Most consumer units need to be fully charged with some regularity.

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They will be charged to 100% every time before I take the boat out, and will then be balanced, so that should not be a problem.
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LiFePo4 is not like the lithium ion in cell phones. Keeping them at low SOC is not needed.
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JohnC avatar image
JohnC answered ·

Hi @baard

Why use V when you have SOC (the BMV) to work from?

Assistants in the Multi can be arranged to switch both ac and mppt chargers between chosen SOC setpoints.

You'll need access to the Multi settings and learn how to use them, but it's an option.

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