Victron's Smart Shunt stopped reading the SOC at 68% and then showed two - - instead of numbers

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friaras asked Aug 17, '22

Victron's Smart Shunt stopped reading the SOC at 68% and then showed two - - instead of numbers

Well, I just learned (from Growatt) the following, and I'm not real happy with this.

"After speaking with Growatt, the data logger will not read an accurate SOC if you are not BMS communicating. Since you have those batteries you cannot BMS communicate, and that is why it reads incorrectly".

The issue is, I have Chins batteries, 8 of them, they got BMSs but the Growatt cannot, determine the correct SOC because the batteries can't communicate with the Growatt (with their communication protocols) so lessons learned if you plan on using the Growatt all in one inverter don't plan on getting a correct SOC unless you have the batteries that can communicate with the Growatt. My bad, nobody said anything about that before, there is no mention as to that on the sellers web-store, don't let it happen to you! Luckily I can use the Chins on my other off grid backup system, and it looks like I'll be getting those server rack batteries they have that can communicate with the Growatt, and hopefully there are no issues with them! Bummer. But then here is the other issue! I have the Victron's Smart Shunt hooked up to the negative side of the Growatt battery bank, and it read the SOC until it reached 68% SOC after that it started displaying two lines (- -) instead of numbers like these ones (- -) no clue what happened there! I ran the bank down all the way until the Growatt low voltage cutoff, so the SOC should have been a lot lower than 68% but all it showed were those 2 (- -) lines. Any comments that will shine some light and help me wake up from this nightmare will be appreciated.

SmartShunt

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liam-hogan answered · Aug 18, 2022 at 11:00 AM

Hi friaras,

How have you got the Smart Shunt connected? To work correctly and accurately it needs to be the last and only thing connected to the combined negative pole of the batteries before going out to the Growatt or anything else you have connected.

Also are these lithium batteries? And each has it's own built in BMS? Are the BMS's connected to each other to synchronise? 8x lithium batteries with separate BMS's could turn in to a balancing nightmare if not properly configured, which could also explain your situation. Having 8 connected together may also exceed the manufacturer's specifications for how many can be synchronised.

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JohnC answered · Aug 19, 2022 at 07:58 AM

Hi @friaras

It sounds like you're disconnecting the power supply to the shunt's electronic module with your daily power isolation. This is the little cable with the fuse holder in it. The effect is probably by design, as the shunt knows it has lost continuity and isn't prepared to continue showing an SOC when it's been disconnected. I'd call it a feature rather than failure.

That cable is always shown in the literature directly wired to the +ve battery terminal, regardless of isolator switching. It's operating draw is specced at "<1mA", so there's no way it'll deplete your batts.

If this is the case, just rewire it.

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friaras answered · Aug 19, 2022 at 04:12 PM

Thanks for the reply. Yes when I disconnect the battery from the Growatt it cuts off all loads, the shunt powers down, The reason I do this is because I don't need the system to be powered up during night time, the Growatt standby consumption is around 30-60 watts and the fans never power down, if left powered on, this causes a battery depletion overnight and the solar charger will kick in as soon as I power up the system the next morning, which is by design and the way I got it setup. But I don't want too many short charging cycles I prefer to drain the batteries at least to 20%, so I disconnect the solar (I have another smaller backup system so I use the solar to charge that one) never waste good solar power! So that the batteries are used instead of solar, once I'm ready to top balance I deplete them to the Growatt's low voltage setting IAW the manufacturer's specifications. The batteries BMSs also consume a little but very minimal, I thought the data was stored on the shunts memory, does it stores history data? If so then it should retain the current SOC data, correct? I can connect the shunt directly to the + terminal on one of the batteries and when I do a power down the shunt will remain powered up, as you mentioned the consumption is minimal if is required for the shunt to retain the SOC data I don't have any issues with that. Is the shunt's memory temporary and does it require constant power to maintain the current SOC data? If so there no mention of this on the manual and like I mentioned on prior post it worked up until the SOC got to the 68% level while I was powering down the system at night time with no issues, then after I changed that setting on the app it started showing the 2 - - lines I'm talking about. I switched the setting back to on, but the 2 lines remained until I took the batteries off the system to top balance them. Once i finish the top balance and I set everything up I'll connect the shunts positive cable to one of the batteries positive terminals and see if it makes any difference(s). Thanks again.

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Alexandra ♦ commented · Aug 19, 2022 at 04:28 PM

https://www.victronenergy.com/media/pg/SmartShunt/en/operation.html#UUID-9975ac10-cdf5-412e-07c1-253aba84ad13

The two - - means it is in an unsynchronized state.

https://www.victronenergy.com/media/pg/SmartShunt/en/operation.html#UUID-128f56e9-f134-182a-e36d-54bece7d8a7a

The only data that is stored in non volatile memory is the history.

It does not assume that is knows the SOC if power has been disconnected. So it will need to resync with your settings.

https://www.victronenergy.com/media/pg/SmartShunt/en/operation.html#UUID-b46e8c9c-ade6-43c6-a192-d7fcd84e12a7

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friaras Alexandra ♦ commented · Aug 19, 2022 at 11:31 PM

Well there it is, that is exactly what is happening, so I'll connect the power wire from the shunt to the positive terminal of the battery bank and it should retain the SOC readings as long as is powered up. Will I have to manually sync after the semi-annual top balance, since I re-configure the batteries to a parallel (12v) configuration and have to disconnect the shunt for that? I use a Victron 30A charger to speed up the balancing, since it takes a few days to charge the bank. Thanks for the assist.

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Answer 1 · 2022-08-19T05:51:57Z

Thank you for your reply! The smart shunt is connected to the negative side of the Growatt straight off the negative battery terminal. The Growatt does not have a built in shunt by the way. The batteries are Chins 8X12v in series parallel in 2 banks, 100ah LiPo4, and setup by manufacturers recommendations. The shunt read the batteries until they were at 68% SOC, then as I normally do in the evenings I shut down the system, all power is shut down and there is no load on the batteries, then I noticed that after power up the batteries SOC read 100% but I knew they were lower, so I let it run for another day and the SOC seemed to have work and was showing about the correct SOC percentage, I then powered down, the next morning I powered up and then again noticed the SOC percentage was at 100% again! I normally power the system up and get it going, in the mornings and it runs for 12 hours a day and powers 2 mini splits AC units to supplement the Central AC unit during the hot summers which is a power hungry unit and we live in TX. At the end of the day I power down the system, rinse and repeat. The batteries are keeping good balance, as good as any other LiPo4 battery. Everything points to the setting on the Victron app, where if you disable this setting and power off then back on as I do it will display just 2 lines (- -) like so, instead of the percentage. I just like to know why have a setting like that? What is the purpose? The manual don't really cover this that well. I learned this from a video I watched and it was mentioned again very casual. At the moment I'm doing the batteries top balancing as I normally do every 6 months or so, but once is finish I'll set it all up and see if it does the same thing. I did disabled that setting and that is when I noticed the SOC on the app was showing the - - lines, is this by design, comments please? I don't have access to the app at this time otherwise I would upload the settings I'm talking about, but it's the one above Synchronization, you can disable that setting and if you do next time you power up the display for SOC shows 2 lines likes so - -.

Answer 2 · 2022-08-21T18:25:06Z

friaras answered · Aug 21, 2022 at 06:25 PM

So for others benefit, I did connected the power lead from the smart shunt to the battery positive terminal in one of the banks, so when I turn the system off at night the shunt remains on, hopefully I can get the smart shunt to read all the way to low voltage cutoff next time I discharge the bank for maintenance. Thanks everyone for the assist!

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Answer 3 · 2022-08-21T21:07:01Z

johanndo answered · Aug 21, 2022 at 09:07 PM

If you cut the power to the shunt, it cannot do anything for you. You shouldn't disconnect your tools when you want reliable information. This is a big issue with all the drop-in batteries with internal BMS, they are unreliable, unpredictable and cannot be managed when they cut you out.

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