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Smart shunt issues

My smart shunt has reporting or other issues. It works perfectly for 1-4ish days. Then the SOC goes blank (see attached pic). Voltage, current, and watts still report. The SOC also disappears from VRM and my Cerbo screen when this happens.

If I charge the batt fully, and click "Synchronize" to 100%. The SOC goes to 100% and counts up/down according to the charge/draw occurring. The SOC will report for 1-4ish days and then go blank again.

Do I have a bad smart shunt? What follow up or testing can I do to determine or fix the issue?


screenshot-20211220-082601.jpg

SmartShunt
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6 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

There is a setting "Start synchronized" if this is disabled the SmartShunt will go to "--" if it looses the power supply.

Do you have a main switch? Maybe the battery cuts off because of undervoltage?

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bluejeans avatar image bluejeans commented ·

LiFePO4 batt. You can see the voltage in the screen shot. No switch between the batt and shunt power

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snoobler avatar image
snoobler answered ·

If the BMS is activating low/high cell protection, it may cut power to the shunt and count as a reset.


I suspect you're discharging to a level that causes low-voltage protection and cuts power to the system.

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bluejeans avatar image bluejeans commented ·

That would be a wrong assumption. Examine the screen shot above. Thats why I included it. I am using a LIFePO4 battery. The voltage is 12.97. So no low voltage protection at the time the reporting quit. I am running a JBD BMS, so I have tons of cell data. No low/high cell activation. The cells run very even, with an almost unmeasurable differential. Especially at the low charge/discharge rates when basically at idle. And as a side note, the issue did not occur over percids of heavier use. Zero issues over the coarse of a year with another shunt. But in the few weeks the smart shunt has been in the system, it is outsmarting a lot of folks with issues and no good answers screenshot-20211220-171323-xiaoxiang.jpg

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snoobler avatar image
snoobler answered ·

The "screenshot above" indicates that power has been interrupted to the shunt. It supports the conclusion of a possible disconnect because 12.97V is a pretty low voltage for LFP under such a low current. This may indicate that you're operating in the lower portion of the SoC range... where one might expect disconnects.


Owning a couple of JBD BMS myself, I can attest to the fact that they don't always accurately count disconnects and may not count them at all.


Given that the installation has changed recently, there could be an issue there as well. Are the pins properly installed in the connector? Crimp or connection issue at the battery terminal?


When you withhold information, you set yourself up for failure. It's no surprise this is "outsmarting" a lot of folks when they aren't given all the information.


Good luck.

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bluejeans avatar image bluejeans commented ·

You can discharge a LFP battery to 10v. Thats how you do a capacity check. The voltage of the screen shot has zero to do with the low discharge rate, and all to do with the time of discharge at any rate, but mostly a higher rate, without a charge. I am trying to isolate the issue to find a common denominator that causes it. But so far, I have not. Only that even though I have kept the phone in front of me nearly continuously, it only happens when I'm not looking

I am not purposely withholding anything. I am frustrated with what should be a simple issue with no answers. I tried to post what I thought was pertinent info. But if I left out something, ask me a question, I'll answer.

The system changed like this. My plan is to convert a hodge podge worth of equipment to Victron. I unbolted the $40 shunt that worked with no issues. I bolted in the $130 Victron smart shunt and something is not right. Tends to make me think it is the shunt. But I am asking what else to check.

A bad connection also occurred to me. That would create heat. I have put the IR gun on every single crimp, connection, battery terminal, and buss bar. Not a single one is over ambient, under load. Not even a little bit. No heat in any of the cells either

My JBD is pretty accurate. If I discharge it 40ah. I can connect a hobby charger and put right at 40ah back into the battery at BMS disconnect. So the BMS nearly matches my charger. And when working, both match the smart shunt very closely. So if the BMS is inaccurate, the charger and smart shunt are all the same wrong

But yet, something aint right

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ bluejeans commented ·
I am frustrated with what should be a simple issue with no answers.
As you can see it is not that simple.

Did you check the setting I mentioned above? Can you make a screenshot of all settings?

The only logical cause for this is that the "Starts synchronized" is deactivated and the SmartShunt is losing power (positive or negative).

OR

The SmartShunt is defective and you should contact the seller from whom you bought it to get a replacement.

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bluejeans avatar image bluejeans Matthias Lange - DE ♦ commented ·
All charging parameters are on Victron factory settings for LiFePO4. The smart shunt "Starts Synchronized" is deactivated now. Originally it was activated. But as soon as any charging began, the smart shunt (SS) went to 100% state of charge instantly. I was beat up by multiple people about how dumb I was for using that setting. So I deactivated it. That solved my issue of the SS going to 100% SOC as soon as charging began. But it did not help the random loosing the SOC


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Nev avatar image
Nev answered ·

Perhaps your BMS LV triggered without your knowledge?

Our 500A SmartShunt has performed perfectly since installation almost a year ago.

Our 4 cell Sinopoly LiFePO4 battery has recorded an all time low of 12.99V during normal operation in 7 years of full-time travel. For our battery I would guess 12.97V = c15% SOC.

The only exceptions are during the 700A+ peak draw measured starting the 3.9l TD engine and during our annual capacity check where the test is terminated when the first cell reaches 2.8V.



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bluejeans avatar image bluejeans commented ·

Something is wrong. But I do not think it can be LVD. After having several random losses of SOC, I turned off all chargers, and all loads to see what would happen. The system set with idle draws, which are only 4w! (smart shunt and MPPT LEDs and Rasbery Pi Cerbo with a fan). It ran 4ish days with super close monitoring. Then lost SOC overnight when I wasn't watching.

For the past several hours I have been running a 30amp load trying to hit LVD. Aint done it yet. And it is lower voltage, with multiple magnitude more load than the screen shots above screenshot-20211221-093725-xiaoxiang.jpg


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bluejeans avatar image
bluejeans answered ·

What is the warrantee time period? I can not find it in the manual

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Nev avatar image Nev commented ·
5 years for mine.
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bluejeans avatar image
bluejeans answered ·

For those interested, the LVD worked exactly as designed. I have the LVD set to 2.75v per cell in the app. I have never gone that low except for a couple of times on purpose like now. But 2.75v gives me power in an emergency should I need it, while still being fairly conservative.

I ran the 30amp load until it went below 2.75v, and the BMS shut it down just as designed. Then I reduced the load to 10amps. The voltage had recovered by a few 1/0ths of a volt per cell while doing that. I ran the load again taking rapid fire screen shots. This was the last shot I got before it dropped below 2.75v (cell 2 hit 2.72v) and the BMS killed the load, exactly as designed.

So with only a 4w load, at much higher voltage when the SOC disappeared, I can not imagine LVD has anything to do with the issue. screenshot-20211221-123506-xiaoxiang.jpg


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