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Chris Sommers asked

Multiplus 12/3000 Low voltage shutdown

Very simple setup - Multiplus 12/3000 connected to a 280ah LI battery bank, fully charged and BMS rated at 250amps discharge. Connected both 2x "positive" / 2x "negative" terminals to blocks using 2 x 4/0 cable for each. I had a 400a fuse on + between battery and block however for testing I eliminated everything that could cause resistance. When I try to run microwave, it will run for a few moments then the whole Multiplus shuts down and complains of low voltage. I also see a DC voltage ripple warning.

Firmware/software updated, checked each connection for tightness, nothing is warm to the touch - I'm at my wits end here. My cheap $450 Chinese inverter handled this with no issues and only one 4/0 cable connected. Not sure what I'm doing wrong?

Any advice would be appreciated!



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Chris Sommers answered ·

After much debate and speaking with tech support from the company I purchased these Eve Grade A 280ah cells from, I decided to bypass the BMS altogether to rule out the BMS or to point the finger at it.

Connected directly to the battery, microwave works, the charging works without shutting down the Victron at full charge, everything works as expected. New replacement BMS on the way (yes, I did order another Daly but I have other options from different manufacturers as well). It's not ideal, but I trust the Victron and its own protection parameters until I get the new BMS delivered.


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nickdb avatar image nickdb ♦♦ commented ·
Have a look at the orions.
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nickdb answered ·

Can you share a bit more information about the battery, make/model or composition, what bms is it?

The issue probably existed for some time, just the cheap inverter didn’t bother telling you.

A likely scenario is a bad cell, that can be a common cause of voltage drops under load, presuming wiring and external issues have been eliminated.

Are you able to connect to the bms? What do the cell voltages read under load/no-load conditions?

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JohnC avatar image JohnC ♦ commented ·
@Chris Sommers

Also look too at the warning/shutdown settings on the Multi. The default shutdown is usually very low and may have been raised to protect the Li batts. Maybe too far..

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Chris Sommers avatar image Chris Sommers commented ·

Batteries are 4x Eve grade A 3.2v 280ah LI cells, sourced from 18650batterystore.com, BMS is a DALY SmartBMS 250amp. This is the SECOND LI battery bank I've tried, after my first admittedly cheaper 280ah DIY build DID have a bad cell.


Settings are:


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Additional screen shot of battery monitor enabled (my bluetooth battery connection to the Multiplus):


1658591624317.png



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nickdb avatar image
nickdb answered ·

Hi Chris, ok. So you have disabled minimum SOC shutdown and the voltage cutoff is super low, equates to 2.3V per cell.

What are you charging at? You would normally aim for around 3.5V per cell.

(sorry missed the 14.13V in the image, doh)

If you're getting down to 9.3V to trigger the cutoff then that's not great.

If you put controlled loads through it and check what the BMS is reporting the cell voltages at, at what load do you get down to 3V per cell?



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Chris Sommers avatar image Chris Sommers commented ·

Hi Nick, thanks for staying with me here.

I have the BMS set for the following protections. The SOC shutdown and voltage cutoff "super low" are both results of trying various ideas to troubleshoot. I'm relying on the BMS (for now) for the protections (which is also cuts off the charge because the SOC from the Victron seems wildly off from the real number and won't stop bulk charging fast enough that the BMS won't shut the charging function down.

I'm not actually sure I'm getting to the 9.3V to trigger the cutoff, because when I try applying load from microwave, the voltages don't budge on the screen for each cell - all stay around that 3.30v range. But I'm also starting to believe the BMS may be the issue here as well - when this happens the only way I get power back is to toggle the discharge switch (3rd screenshot below).


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nickdb avatar image nickdb ♦♦ Chris Sommers commented ·
You’d expect an A grade battery to hold its voltage under the desired load. So if that is the case, then something may be off with your BMS or its config if it is disabling discharge. I’m not familiar with Daly so hopefully someone else can chime in.
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Chris Sommers avatar image Chris Sommers nickdb ♦♦ commented ·
It was the BMS. Replacement coming! Thanks Nick!
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Paul B avatar image
Paul B answered ·

I would suggest you look at a 123 smart BMS or a rec BMS - Daly BMS units can only balance at 0.035ma way to low for your eve batteries.

Daly has a inbuilt fet as a cutoff, the 123smart or rec both use external relays. plus if you have a GX unit in the system then the relays may not even be needed when using a 123 smart or Rec BMS (I prefer 123 smart) as the inverter/charge is directly controled by the BMS units through the GX device

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