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cmorewood avatar image
cmorewood asked

Help getting the best out of my sodium (salt water) batteries

The System 5.2Kw PV with a Fronius Primo 4-1 inverter interfacing with a Victron MultiPlus 48/5000/70-100 an a CCGX Gateway, 2 x Aquion S30-0080 48v batteries.

I'm new at this. The batteries have only been up and running for 2 months so I'm learning about them every day. I'm trying to get the most out of them, that is charging to 100 % and discharging to near zero every day. However the Victron unit is, I'm sure, preventing this as It's not designed to work with sodium batteries.

My problem is that unless the batteries have a 100% SOC for at least an hour during the day they will only discharge to a relatively high percentage SOC.

In the summer where the batteries have a 100% SOC every day the batteries will discharge to about 11%. ( I was hoping for lower)

At this time of year I'm rarely getting a 100% SOC via Solar and so have to use scheduled charging. However as soon as the charging is finished the discharging starts . But only to about 60-70%.

I'm beginning to think that there is a battery life protection built in to the Victron unit even though it is disabled in the CCGX.

My options/questions:

How do I enable scheduled charging and get the SOC to remail at 100% for at least an hour?

Is there a battery life protection built in within Victron?

Can I turn off battery life protection within the Victron?

As you can see in the first image, as soon as the SOC is 100% for about an hour (10-1100 )the battery will discharge more, down to about 40%. the other attachments show what happens if I can't get that magic hour of 100% the discharge is between 60 to 70%.

If the battery doesn't achieve 100% SOC the I'm left with about 80% SOC

I am planning in the winter to charge the batteries with cheap grid electricity at night, but if I cannot get the !00% SOC to last for more than a few minutes the batteries will never discharge fully, which is one of the reasons I chose the sodium batery.

Any advice gratefully received.

Thanks,

Chris

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Battery Protectdischarge levelAquion
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4 Answers
JohnC avatar image
JohnC answered ·

Hi CM. Aquions are a bit of a rarity here, and I'm guessing too.

But I'm sure that custom settings in the Multi charger can do what you want if you define them correctly.

Your SOC worries me though. Unless you've a BMV (or some unknown bms), then you're likely sourcing that from the Multi (via the GX). That's not really adequate for total reliance, as it's quite coarse, and even then would need setting up to suit your batts.

Nor can I find sense in what it's showing. On your centre graph, it's even rising with loads on?? What's happening there??

I'd ignore SOC, and maybe delve deeper into VRM Advanced to select more useful graphs ('widgets' if you've never done it). Voltage, and time spent there is what you want to see for batt health.

But come back, plenty help available here with full info. Most of us don't like guessing, so mostly we don't..



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cmorewood avatar image
cmorewood answered ·

Thanks for your reply John,

The center graph is showing a sheduled charge plus the usage from the heat pump 2200 and 0530 which just happened to be at the same time on that day. ( I forgot my system time is setup on GMT) I try to keep the large useage events apart to avoid the high peaks, but I'm still educating the family as we've just moved from gas and this is the first Autum of the new regime.

I understood that the Aquions didn't need a battery monitor and they could be left to their own devices as no harm comes to them when they're discharged fully. I wanted simplicity which is partly why I chose them.

I don't have full control over the Victron System. I merely have monitoring control so there's only a few parameters I can change, The installation engineer has full control and as this was his first sodium installation, he's experimenting with the settings as well. I believe he has used the settings which Victron recomend for the Aquion and Greenrock batteries.

I thought I'd try to find out if there was anyone ion the Victron site who was having siimilar problems and how they'd solved them, so I could then pass on the information to the engineer. He's busy enough without me bothering him all the time with problems. If I can give him solutions to the problems, we can both learn.

I've attached the advanced page from the last 24 hours. I think this is what you were after John.

It has the scheduled charge times of 2100 0400 and 1100. I'm trying the 1100 to get at least an hour of charge into the batteries using the most productive solar period, so that I can increase their yield in the evening but as you can see, today, even with over an hour of 100% SOC the discharge stopped at 60.5%.

Unfortunately John I'm completly new to this and although I enjoy a challenge, this is a steep learning curve for what I thought would be the simplest of battery setups.



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JohnC avatar image JohnC ♦ commented ·

Ta Chris. The pics help, and you've selected them well. My random gleanings:

* Your Multi is cutting out at 41V, and your loads are then reverting to grid supply. 41V is awfully low, and (without looking it up) insufficient to keep it operating.

* Hence your SOC halts it's decline. It may not be at the point you desire to see, but it's being overridden by V.

* You (or your installer) could adjust the calculation parameters of the SOC in the Multi. Maybe lessen the batt capacity, or tune it's sync point under charge. You can make it show anything you want, as it's a calculated figure. I'd ignore it for now..

* Your system likely has ESS assistant installed. Bedtime reading for the benefit of your learning curve: https://www.victronenergy.com/live/ess:start

Victron pulled it's Aquion compatibility page, but this remains: https://www.victronenergy.com/live/battery_compatibility:greenrock

Maybe someone else with Aquion experience can chime in..



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cmorewood answered ·

Success!! I think I've proved that if I force the batteries to stay charged for a few hours I can get a deeper discharge, 37%SOC yesterday as opposed to the 60-70%SOC not using the technique. There must be a battery protect built into the ESS programming even when it is switched off?

I'll now delay the 2000 sheduled charge to see if I can achieve a deeper discharge today.


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JohnC avatar image JohnC ♦ commented ·

Please try to be clear here. There is no 'battery protect' at play. The inverter is simply cutting out at that dreaded ~41V, and reverting to grid. It's still doing that.

Your 'success' is simply the longer length of time the batts have been under charge, and in better condition for the SOC to start it's decline.

If you really *must* look at SOC, try setting it's 'State of charge when Bulk finished' away from the default 85% (and I think I can see a kink @85% in your SOC graph under charge), say down to 50% as a test. Then you can watch it rise if the batts are still charging usefully. If the charge curve flattens at say 80%, adjust the 50% up by the shortfall (20%) to 70%. That should bring you closer at least to a little more meaningful figure.


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cmorewood avatar image cmorewood JohnC ♦ commented ·
Hi John, So as I understand it, you're saying that 100% SOC is not actually a full battery and they continue charging after 100% is reached and there is no direct relation between SOC and battery voltage?


As I said I'm new at this and this is opening my eyes a bit. I'll have to go and watch a few youtube videos on the subject.


I don't have access to the "SOC when bulk finished" I'll have to wait for the engineer to adjust that.

At least I've found a way to get the batteries to give a meaningful discharge, currently south of 38% 41.77V and 11.6a.

Thanks again,

Chris




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klim8skeptic avatar image klim8skeptic ♦ cmorewood commented ·

Hi,

What is actually measuring the SOC? The battery's bms?, the multi? a BMV?

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JohnC avatar image JohnC ♦ cmorewood commented ·

"So as I understand it, you're saying that 100% SOC is not actually a full battery and they continue charging after 100% is reached and there is no direct relation between SOC and battery voltage?"

Yeh Chris, exactly. To illustrate, look at what happens to SOC when you apply batt charge - it bolts upward very quickly to 100%, then the batts keep accepting charge. So can't be 100%, hey? Then when has reached Absorb V the charge tapers, and can be seen starting to level out to about 500W, when the charge seems to drop into Float mode. Still not fully charged, but SOC showing 100%. Raises the question too - is it supposed to go into Float that early?

Klim asks a valid question, and I've assumed (I shouldn't do that) VEBus-derived-SOC because of it's behavior. A bmv wouldn't act like that, and the 'bms' that may have come with the Aquion isn't Victron compatible.

I'm glad too that your eyes are opening. Tis why you asked, isn't it? :)

For research, check too Victron's flagship BMV700 series, to gain an inkling into what's involved setting up a useful SOC: https://www.victronenergy.com/upload/documents/Manual-BMV-700-700H-702-712-EN-NL-FR-DE-ES-SE-PT-IT.pdf

And oh, if you'll pardon me a side-observation. Your solar doesn't appear to be being fully utilised, instead the grid is doing most of the work. Can't see your weather from here of course, but maybe something to watch..

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cmorewood avatar image cmorewood JohnC ♦ commented ·
Sorry guys, Been busy on the house for the past couple of days. I've been keepng to the regime of "keep batteries charged" during the day for about 5 or 6 hours with a top up at 0400 and I seen to be getting between 4 - 6 hours of discharge before reaching the 40.8V limit.

Klim, I 'm not sure what is measuring the SOC. I would assume that would be within the Victron unit, there was no BMS that came with the Aquion.

John, the weather here was a bit crap for the periods you can see the graphs. Its been a bit more sunny over the past few days but the days are getting shorter and now a perfect day, 10 hours of solar only gives 3 hours above 3kw and under 19kw daily total.

The dark winter nights will give me plenty of time to do some more eye opening reading ;-).

And now you have me looking into Peukerts law!!

Keep the comments coming. Thank you.



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JohnC avatar image JohnC ♦ cmorewood commented ·

Yeh, perhaps I shouldn't have pointed you at the BMV, it's Victron's high-end batt monitor, and might confuse. What you're likely using is much simpler and coarser, but still might be useful. You may have access to it via VRM if your installer hasn't cut you out of it.

Go VRM > Device List > VEConfigure and follow the prompts. It will download a .rvsc file which you change and send back, so it's not updating directly.

This is what it will look like on the 'General' tab:

An old file from my own system on old firmware, so yours might be a little different. See 'Battery monitor', and the '85%' I mentioned earlier. Try dropping that to (say) 50% and you'll be able to watch SOC rise & taper, rather than just hit the 100% wall. Then tune the 50% so the charge taper finishes at 100% or close to.

The 'Battery capacity' could be adjusted too to give the full real-world SOC range between the 100% and 0% at 40.8V (effectively flat batts).

Simple it is, and coarse. But if you're going to rely on SOC, then essential, at least to understand what influences it and how you have great control over it.

And oh, by all means have a look around in there, but best not to touch anything else til you know exactly what you're doing. :)

If ESS has somehow been linked to the SOC, then revert to original settings. I suspect not, as it hasn't been set up optimally anyway..

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cmorewood avatar image cmorewood JohnC ♦ commented ·

Hi John, Thanks for the reply. I don't have access to that, thanks for trying. I just have a list of devices and can open them up but have no access to Ve Configure or anything that looks like that unfortunately.

On another note, I have been looking at the Greenrock videos on Youtube. I can't figure out whether they evolved seperately to Aquion and then took over their sales when Aquion went bust or not, but the battery stacks look the same. Anyway one af the videos was takling about battery temperature and how they don't like the colder temperatures and are more efficient at higher temperatures so with my batteries being in a garage and a draughty one at that were temperatures in the winter inside are sufficient to freeze the insulated plastic pipe to the water tap. I have seen -26 c twice in 12 years and below -15C every few years.

So I have wrapped them in some spare Actis multilayer insulation, open at the top, with a block of wood each side to allow airflow and put a dual temperature monitor on them, one between the stacks and one on top.

This morning when the outside temperature was just above freezing the garage was 5C, the temperature between the stacks was 35C ad immediately above the stacks was 20C hopefully improving their efficiency over the winter.

Klim, Its the Multi doing the battery monitoring, which I have no access to.




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klim8skeptic avatar image klim8skeptic ♦ cmorewood commented ·

It is a bit hard to find any technical specs of the Aquion battery. https://web.archive.org/web/20160415000000*/aquionenergy.com

A bit more digging, https://covertelpower.com.au/wp-content/uploads/2015/05/S30-0080-Product-Specification-Sheet.pdf

https://www.emarineinc.com/Aquion-S30-0080-Battery-Stack

https://provisionsolar.com/wp-content/uploads/2016/10/Aquion-S-30-Battery-Data-Sheet.pdf

Continuous discharge power per stack 680w.

You supplier could probably explain better.


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cmorewood avatar image cmorewood klim8skeptic ♦ commented ·
Thanks klim, I'd seen most of those. I'm waiting for the installer to get back to me. I have discovered that if I force charge for 5 or 6 hours till we're down to under 5 amps then I can get discharge down to 15%SOC before the dreaded 40.8V kicks in. I think I'll be getting another 2 batteries as these two just don't provide enough resilience. I've been dithering about whether one or two would be better but I think I've decided on 2. I've been searching the web for Aquion owners with Victron Multis. Not a lot of luck so far. hopefully Blue Sky with their Greenrock system will make in roads into that. Their EMS is very very interesting.


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JohnC avatar image JohnC ♦ cmorewood commented ·

Perhaps time to push your supplier to give you access. Dunno your arrangement there, but it wouldn't suit me as the owner.

Restricts how we can help too..

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cmorewood avatar image
cmorewood answered ·

I found this manual online for the Aquion S series.

www.altestore.com/static/datafiles/Others/Aquion_S30_M110_Installation_Operation_Manual.pdf


Thought it might help someone

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