question

pigwet avatar image
pigwet asked

Multiple VE.CAN MPPTs only enter absorption one time

I recently added a second VE.CAN 250/100 MPPT to my system. They are synchronized, connected to themselves and my Cerbo GX with Victron brand ethernet cables and two terminal plugs. All settings are identical on the MPPTs, and the device instances are the same. The slowly blinking synchronization symbol is present on the MPPT screen.


With the addition of the second MPPT, absorption & float are achieved correctly the first day after connecting the batteries. However, on the second and subsequent days, absorption is skipped and they go directly to float. They also don't reset the BVM to 100% as it quickly switches to float. I've read online that they are not recognizing "nighttime" correctly. However, the state of the MPPTs at night are "off", and there's no stray light powering any of arrays. At most they produce 0.2V during the night.


So, my solution thus far is to disconnect the batteries/solar from the MPPTs to reset them, and start them back up. Not a fun thing to do on a daily basis.


What more can I check to fix this?

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MPPT Controllers
state.png (24.7 KiB)
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12 Answers
pigwet avatar image
pigwet answered ·

This worked! Thank you all. The Ve.smart network was deleted and I turned on DVCC in the cerbo. Both MPPTs have entered absorption 3 days in a row.

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Alexandra avatar image
Alexandra answered ·

@pigwet

Been mulling this over since i saw the post.

For the same time period what are the amp volt graphs for the battery?

One of two things i can think of here, it is going into absorption and not reporting correctly. Or bmv charge detection or tail current is triggering the full charge early, bmv is telling the cerbo which switch the state on the mppts.

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pigwet avatar image
pigwet answered ·

Thank you Alexandra. Added voltage/current of battery. Will do screenshots of the MPPT settings in a bit. I do have tail current disabled in expert settings.

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Alexandra avatar image
Alexandra answered ·

Is dvcc enabled on on the cerbo?

And on the mppt in expert have you set an fixed absorption?

Are there any other components in the system?

And is tail current on the bmv disabled as well or just on the mppts?

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Alexandra avatar image
Alexandra answered ·

@pigwet

This was the widget I was looking for.

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pigwet avatar image
pigwet answered ·

Current and voltage.

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capture6.png (38.5 KiB)
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pigwet avatar image
pigwet answered ·

Is dvcc enabled on on the cerbo?

No. I used to have it enable with one MPPT but wasn't using the charge limit feature so I disabled it.

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And on the mppt in expert have you set an fixed absorption?

Yes. Fixed at 1 hour...on both MPPTs.

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Are there any other components in the system?

BVM, two MPPTs, two Multiplus running split phase 240V.

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And is tail current on the bmv disabled as well or just on the mppts?

This I don't know. I will have to bluetooth into it when I get home to see. I don't recall this being a setting but I'll absolutely check.


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Alexandra avatar image
Alexandra answered ·
@pigwet

What batteries are there?

My other question is what is the notification on the GX there?

And are all components up to date?

So etimes it doesnt play nice when half is up to date and half is not.

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pigwet avatar image
pigwet answered ·

I have 8 battle born batteries. The warning was just a low battery voltage at the time. All the components are up to date except for the inverters (don't really want to mess with them since they are working fine).

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Below are the BVM settings (sorry for volume bar over settings). Tail is 4%, charged detection time is 1min, peukert is 1.05, charge eff is 99%, current threshold is 0.1A.

The one thing I'm seeing in the manual is that charged voltage should be a bit lower than float voltage, not absorption voltage. Most suggested settings online for battleborn/BVM have charged voltage above the float voltage. Perhaps this is causing an issue, but again I had it setup this way prior to adding the second MPPT.

When the batteries near full charge, they hit 28.8V and then quickly drop to the float voltage of 27.2V, not allowing the tail current + charged voltage to be observed by the BVM for 1min. So I can see how this would not let the BVM reset to 100% reading, but not how or why there's not trigger to go into absorption.

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pigwet avatar image
pigwet answered ·

I have 8 battle born batteries, 4 groups in parallel. The notification was just a low voltage warning at the time. All the components have the latest firmware.

Below are the BVM settings. The tail current is 4%, charged detection time is 1 minute, puekert 1.05, charge efficiency 99%, current threshold 0.1A.

There is no way to disable tail current in the BVM from what I can tell, the lowest setting is 0.5%. From the manual, the BVM will read 100% when the charged voltage of 28.4V and tail current is lower than 4% of 396A or 15A, for at least 1 minute. Battle born suggests 2%-4% tail current. Clearly when the system switched to float instead of absorption, the voltage changes from 28.8V to 27.2V very quickly, and the BVM does not read out 100% state of charge. But not sure how this is related to not switching over to absorption.

Also in the manual it states that the charged voltage should be a few tenths lower than float voltage (27.2V) - but I've never had it setup that way. I've always had it set to a few tenths lower than the absorption voltage (28.8V)

There's a few links with suggested values, all of course a slightly different.

https://static1.squarespace.com/static/562bc73de4b0908330f67ee0/t/603ed19c77c17912ac07fe71/1614729628929/BMV-712+in+App+for+Battleborn.pdf

https://battlebornbatteries.com/configure-victron-bmv-700-bluetooth-dongle/

https://amsolar.com/rv-solar/support

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nebulight avatar image
nebulight answered ·

Side note, I think I saw your youtube video on charging your tesla with this setup. As @Alexandra said, I believe you need to have DVCC turned on in order for the sync to work (I've never used VE.CAN MPPTs so I may be remembering this wrong). However if you setup a VE.Smart network, you need to disable that first.

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pigwet avatar image
pigwet answered ·

I turned on DVCC in the Cerbo and deleted all the devices in my VE.Smart network using the app. We'll see how it does over the next few days.

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