New useful DVCC-function: switching to float-voltage - @Victron: Can you do that? :)

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puitl asked Mar 29, '22

New useful DVCC-function: switching to float-voltage - @Victron: Can you do that? :)

Hi my dear Victron-Experts!
[@Victron]

Loading to the absorption-voltage and after that switching to float-voltage is a really useful function from you : At first higher voltage for fast charging and top-balancing and after that switching to the gentle float-voltage.

BUT
I have a Seplos-BMS for example which only has a fix CVL, so the battery always stays at the absorption voltage which is not very gentle.

I have seen in the VRM that the "VE.Bus state [276]" is also switching from bulk to absorption when the CVL is reached, therefore i have the wish for you to add following "DVCC-float voltage" function:

Activating the new switch "Individual float-voltage" is showing the following two adjustable parameters:
- float voltage
- max. absorption time
(like in the VEconfig)

Function:
After one to seven hours (adjustable) staying in absorption, DVCC pretends the set float voltage as new CVL > only when BMS-CVL is higher of course
(the same like with the DVCC-function "max. charge voltage"...)
When discharging the state is switching into bulk and the game starts over :)

What do you mean?
I think this function would be perfect :)

Thank you!

DVCC feature request

2 |3000

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Modifications Space

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Answer 1 · 2022-03-30T13:51:44Z

puitl answered · Mar 30, 2022 at 01:51 PM

A less "User-complicating" option could be to take the values for "max. absorption time" and "float-voltage" from the VEconfig-settings which are done from the expert usually ;)

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Answer 2 · 2022-03-30T20:52:51Z

Daniël Boekel (Victron Energy Staff) answered · Mar 30, 2022 at 08:52 PM

Hi @Puitl

If you use a CANbus connected battery, charge voltage is set by the battery. so if you have LFP cells you need the battery to send a lower CVL

Bulk / Absorption simply means:
-Bulk = CVL not yet reached (CC)
-Absorption = CVL is reached (CV)

3

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puitl commented · Mar 31, 2022 at 06:17 AM

@Daniël Boekel (Victron Energy Staff)

...thats all clear BUT:

My CANbus connected battery only sends a fix CVL (56,8V = 3,55V cell) and I have no hope that the manufacturer will optimize here anything.

Fact 1
With the DVCC-Option "Max. battery charge-voltage" you give the normal interested user the chance to reduce the CVL related to the value which comes from the BMS.
So we can assume that the user know´s what he´s doing here.

Fact 2
When the CVL (from BMS or DVCC) is reached your internal VEstate switches from bulk to absorption, after the first little discharge it changes back to bulk - so the system recognice it whats going on.

My wish
New DVCC-Option to activate a lower float-voltage (for example after one hour staying in absorption-state) - completely the same as the ESS do it without any BMS.
For you it´s "only" a little expanding in the software and for a lot of users it´s getting back a important feature for saving there batteries when using a Canbus-BMS which is not programmed intelligent enough...

What can happen? - Nothing:
If the User is activating this option we can assume that he knows what he´s doing and he can realize a float-voltage when the BMS doesn´t have this option.

Whats happening when this option is activated and the BMS DOES have its own float-function here? - Nothing:
The system takes the lowest voltage (BMS CVL or DVCC-float) which it is finding, exactly the same like DVCC-Option "Max. battery charge-voltage"

The first little discharge is setting VEstate bulk and this is deactivating the DVCC-float until beeing the next hour in absorption-state.

I hope you will implement this!
Please give me feedback.

Thank you very much and best regards
Leo

2 ·

nickdb ♦♦ puitl commented · Mar 31, 2022 at 02:49 PM

On most BMS's you can access it via a serial port and BMS software. Once in, you could set what you want. It would ruin your warranty but you can do it.

0 ·

puitl nickdb ♦♦ commented · Mar 31, 2022 at 03:03 PM

@nickdb i have the Seplos. What do you mean exactly? With the PC-software i can set a lot parameters but functions like described above are not possible without "re-programming" the board...

0 ·

Answer 3 · 2022-04-07T06:33:21Z

puitl answered · Apr 07, 2022 at 06:33 AM

Hello Daniel!

Any Interest in implementing something here?

Best regards

1

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Daniël Boekel (Victron Energy Staff) ♦♦ commented · Apr 13, 2022 at 07:37 AM

This has to be done by the battery manufacturer, not by Victron.

What you can try is VenusOS.Large, maybe you can set DVCC maximum charge voltage but I don't know if that is possible.

Also look at how REC BMS works...they implement something that stops charging at some point.

1 ·

Answer 4 · 2023-01-13T05:01:31Z

Andy answered · Jan 13, 2023 at 05:01 AM

I got the same problem with the Seplos BMS and keeping the battery at absorption voltage forever. Even there is a float voltage set in the MPPT, it will be ignored as the charger is under external control when using a Smart BMS.
I am in contact with the Seplos engineers and they don't understand why we would want to float a lithium battery. So there is no hope that this ever will be implemented from their side.

I guess, I won't be using their products any more as the whole design and implementation sucks.

8

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pedaaa commented · Jan 13, 2023 at 06:48 AM

in my opinion these chinese manufacturers are not able to understand or invent anything like this on their own.

All they do is copying from bigger or better companies.

So... the best way to request new featues from a China-manufacturer is to tell them a BMS-brandname that has your wishlist feature included, send them details & manuals about it, and tell them to copy it.

Sad to say, but that seems to be the best way to success.

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Answer 5 · 2023-04-20T20:45:19Z

derrick thomas answered · Apr 20, 2023 at 08:45 PM

Really easy to do in node red. I have a flow myself which tracks the voltage and tail current, and when it meets my requirement I set the max charge voltage to a lower 'float' setting.

4

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juf commented · Apr 21, 2023 at 08:44 AM

@derrick thomas

pls. Can you share your flow

have a bms who have the same not sending float.

regards

0 ·

derrick thomas juf commented · Apr 21, 2023 at 03:30 PM

https://github.com/thomasinaz41213/BMS-charge-control

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juf derrick thomas commented · Apr 21, 2023 at 04:49 PM

Thx very helpful

0 ·

brecht derrick thomas commented · Feb 20 at 10:08 PM

I just checked this link and it looks dead... is there a possibility to still share this flow? @derrick thomas or @Juf . Would be very interested also

0 ·

Answer 6 · 2024-02-21T08:27:52Z

That's how I do it with the help of NodeRed:

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New useful DVCC-function: switching to float-voltage - @Victron: Can you do that? :)

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New useful DVCC-function: switching to float-voltage - @Victron: Can you do that? :)

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