Hello

Does anyone have any ideas what might cause these strange steps in my battery SOC?

Thanks

What battery is this and how is it communicating with the inverter? If the inverter uses the battery voltage to estimate SOC then those dips can be due to increased current draw in the house. It looks like the battery is run down to 60% at noon before being charged to 95%.

Hi @frivan, thanks.

Interesting, that time of the night the house is pretty stable, 2 fridges and not much else. I included consumption in the chart.

Deye 5KW inverter
2 x Volta Stage 1 5.12 KWh batteries
8 x Astroenergy all black mono half cut 400W panels

In terms of how it's communicating with the inverter, I'll take a look, but it looks like an ethernet cable. What should I look for?

yip, we've been having a lot of rainy days recently, so I top the battery up from the grid after midday (if there's no sun) to avoid sitting on our 45% reserve day after day.

Edited June 12, 20233 yr by splunker
added tag and chart

1 hour ago, splunker said:

but it looks like an ethernet cable. What should I look for

The cable is a good start. The inverter should be set to lithium under batter settings. Also, the inverter must get charge limits under the Li-BMS menu.

The BMS has to guess the SoC between high and low battery voltages, because the LFP voltage versus SoC curve is nearly perfectly flat between 20% and 80% SoC. So it drifts a bit, then when the battery is full the BMS realises oops it's not 95% SoC, it's now 100% SoC. This is common and normal.

Hopefully over time, the BMS will learn the true capacity of the battery and track it well. When the battery is new, it's still balancing for the first few weeks.

There is a quite small chance that one or two cells are sub par, so it's worth keeping an eye on. 

Thanks very much.

@frivan, looking at the inverter settings, the battery is indeed set to Lithium, and the battery information is linked with an Li-BMS menu in the lower right corner, so I think that seems good.

@Coulomb thanks, that's interesting. Reading around what you wrote a little I get the picture that SOC is an algorithm based on voltage as well as ongoing tracking of power in (and power out?), and every now and then it self corrects. (https://revov.co.za/news/voltage-vs-soc-lifepo4-charge-discharge-curves/). I don't follow it all, but it starts to fill in the picture.

I was more referring to the ups and downs between midnight and 4am though, but perhaps this is the same thing.

I was watching it the following night, and the SOC flatlined for several hours while we were using power which was odd. continued into the next day, and sort of corrected itself later on. I guess that could also happen for the reasons you described.

I guess I'm worried that if the inverter (or the BMS) doesn't know what the battery levels are, it could potentially overcharge the battery.

Thanks

A quick update, this evening, I noticed some water in one of the RS485 plugs 😭.

We've had some crzy weather here recently, and I suppose the water found a way in.

the plug had some bluish ooze coming out of it.

The installer popped round, told me to fix the leak (duh) let the plug dry out and not to worry about it unless the battery sets off an alarm.

I guess its conceivable that this is/was interfering with the comms.

What happens if I remove that other RS485 plug to see if the plug hole is dry?

Thanks again

Switch off the inverter and batteries. Unplug the cable. Use a hairdryer and dry out the ports at 50% heat. Reinstall the cable and restart. Put tape over all ports and holes.

Is it safe to just switch it off? Do I need to turn off any trip switches? Installer was very strict about me never touching anything. 

7 hours ago, splunker said:

I was more referring to the ups and downs between midnight and 4am though, but perhaps this is the same thing. 

The ramp up is the inverter utility charging the battery. There is something special about 95% SoC, I think it stops there if its calculation says it should be higher than 95%, but the battery voltage isn't high enough for that to be realistic. Once the battery voltage is high enough, then it changes instantly to 100%.

I would definitely use something to remove the blue oxide from the RS485 port. Preferably contact cleaner, but oil based spray at a pinch. Gently dry out with a tissue or cotton bud. 

10 hours ago, splunker said:

Is it safe to just switch it off?

Flip the Change Over Switch (<30ms). Switch off the inverter. If solar is 0W, isolate. Switch off the supply to the inverter. Switch off the battery (including breaker on the battery)... that should be a safe way to do it.

Edited June 15, 20233 yr by frivan

On 2023/06/11 at 10:12 PM, splunker said:

Hello

Does anyone have any ideas what might cause these strange steps in my battery SOC?

Thanks

It would be super useful if you could add the Battery Voltage and Battery Current to the chart as that will give us a better idea what is going on. Also, if you want to do an experiment, watch the SOC as you plug in and plug out the BMS cable, does the SOC jump around when you do that?

Another thing, it is very difficult to calculate an accurate SOC, there are many factors that influence it such as battery chemistry (NMC, LFP, etc), temperature, battery internal resistance, age of battery, etc. So SOC jumping around a bit is expected and normal. One way to make sure your SOC is "accurate" is to make sure you fully charge the battery every now and again as that teaches the inverter where 100% SOC is if that makes sense.

Get some IPA and a stiff art paint brush. Clean out that port and dry with hair dryer. Use a new network cable. 

Check other ports as well. 

Hello everyone, thanks for all the info and suggestions.

Spent the last week sealing the roof, putting a new ceiling in the garage and building an extra cupboard over the inverter and batteries (plenty of air holes, but hopefully zero water).

So far the only thing I have done is very gently dry the oxidised plug with with a hairdryer (on low). It's bone dry. I have some switch cleaner, and isopropyl, but I haven't tried cleaning it in case I accidentally push a contact against another one. 

@frivan, I haven't had the courage to switch the inverter off yet. I managed to get some instructions out of my installer to bypass the inverter, and I think this ties in with your procedure, but I'm not 100% so would like to go over it to see if the instructions make sense please.

1. AC IN - off (cuts grid power to the 3-way Changeover switch)
2. Changeover Switch to Eskom (is this the the <30ms switch?)
3. AC In - back on (Grid power to Changeover restored, now bypassing the inverter)
   1. At this point, if I understand, the grid power is not going to the inverter, but the inverter is still providing power via solar/batteries.
4. Solar DC breaker - OFF (cuts solar power off to the inverter)
5. Switch off the inverter.
   1. now the only power to the house is from Eskom
6. Switch battery power off on both batteries.
7. Switch battery breakers off.

Then I can remove the ethernet plug and check that port, clean etc.
Plug all back in, and then reverse the switches.

@Chris_S, thanks for the suggestion, stiff art brush makes sense. Is the wiring on this cable standard ethernet wiring?

Hi @HendrikBigChief, thanks!

I cant see an option to add battery V or A to the chart unfortunately. I've added battery power in KW, does that maybe tell you something? it seems like some small dips in power correlate to changes in the SOC, I suppose things are still balancing?

 

I also saw that my installer left Activate Battery ticked, and I believe this should be disabled at some point? The batteries are about 4 weeks old now.

Thanks very much for the info. I'm realising what you said now, how the SOC is not a straightforward measure, but more of an algorithm, and there're a lot of factors. It really makes me want to increase the shutdown % from 10% to a little more than 20% (the cycles rating is to 20% like most batteries I think) to allow for a bit of error...

Out of interest then, is it the BMC in the batteries themselves that control when to accept charge/not, preventing overcharging etc.

Cheers

46 minutes ago, splunker said:

Hi @HendrikBigChief, thanks!

I cant see an option to add battery V or A to the chart unfortunately. I've added battery power in KW, does that maybe tell you something? it seems like some small dips in power correlate to changes in the SOC, I suppose things are still balancing?

 

I also saw that my installer left Activate Battery ticked, and I believe this should be disabled at some point? The batteries are about 4 weeks old now.

Thanks very much for the info. I'm realising what you said now, how the SOC is not a straightforward measure, but more of an algorithm, and there're a lot of factors. It really makes me want to increase the shutdown % from 10% to a little more than 20% (the cycles rating is to 20% like most batteries I think) to allow for a bit of error...

Out of interest then, is it the BMC in the batteries themselves that control when to accept charge/not, preventing overcharging etc.

Cheers

Hello,

So the Battery Voltage and Amps chart is here:

On the Solarman app, go to Device on the left:

 

Then click on the inverter that is listed on the right. Then scroll all the way down, you will see a chart like this:

 

This chart does have the battery voltage and battery current:

-------------------------------

So the Activate Battery setting should be ok to leave on. That just helps it if the battery dies completely.

-------------------------------

The issue you have (my best guess without battery voltage chart) is that your SOC is estimated higher than what it actually is. This is a very common issue. The solution is to ensure you fully charge your batteries once a day. So in your work mode screen on the inverter, make sure you have a few hours a day scheduled where the battery is set to 100% and grid charge is ticked. I do mine at the end of the day from 6pm to 10pm. Then I know the battery is full and the SOC will then be correctly calculated.
 

Evening @HendrikBigChief

Thanks very much for all this. Found what you described...

I'm very interested to hear what you think when you see this. 

Thanks for the Activate battery info.

Ok, so it's estimating a higher SOC, and then sort of glitches a bit as it self corrects. I'll take your advice on the recharging. I currently have it set to charge to 95% 12:00-16:00, my thinking is that it sort of simulates a sunny day. If there is a sunny day (ever again) the solar will charge the battery, but if not the grid can push it up. Will change it to 100% for tomorrow and see what happens next.

Thanks again for the info and patience.

 

14 hours ago, splunker said:

Hello everyone, thanks for all the info and suggestions.

Spent the last week sealing the roof, putting a new ceiling in the garage and building an extra cupboard over the inverter and batteries (plenty of air holes, but hopefully zero water).

So far the only thing I have done is very gently dry the oxidised plug with with a hairdryer (on low). It's bone dry. I have some switch cleaner, and isopropyl, but I haven't tried cleaning it in case I accidentally push a contact against another one. 

@frivan, I haven't had the courage to switch the inverter off yet. I managed to get some instructions out of my installer to bypass the inverter, and I think this ties in with your procedure, but I'm not 100% so would like to go over it to see if the instructions make sense please.

1. AC IN - off (cuts grid power to the 3-way Changeover switch)
2. Changeover Switch to Eskom (is this the the <30ms switch?)
3. AC In - back on (Grid power to Changeover restored, now bypassing the inverter)
   1. At this point, if I understand, the grid power is not going to the inverter, but the inverter is still providing power via solar/batteries.
4. Solar DC breaker - OFF (cuts solar power off to the inverter)
5. Switch off the inverter.
   1. now the only power to the house is from Eskom
6. Switch battery power off on both batteries.
7. Switch battery breakers off.

Then I can remove the ethernet plug and check that port, clean etc.
Plug all back in, and then reverse the switches.

@Chris_S, thanks for the suggestion, stiff art brush makes sense. Is the wiring on this cable standard ethernet wiring?

Yes standard ethernet cable

11 hours ago, splunker said:

Evening @HendrikBigChief

Thanks very much for all this. Found what you described...

I'm very interested to hear what you think when you see this. 

Thanks for the Activate battery info.

Ok, so it's estimating a higher SOC, and then sort of glitches a bit as it self corrects. I'll take your advice on the recharging. I currently have it set to charge to 95% 12:00-16:00, my thinking is that it sort of simulates a sunny day. If there is a sunny day (ever again) the solar will charge the battery, but if not the grid can push it up. Will change it to 100% for tomorrow and see what happens next.

Thanks again for the info and patience.

 

Thanks for the chart. It seems that your Battery BMS is doing a better job than most other batteries. It looks like the SOC spikes you are seeing is the BMS doing minor corrections of the SOC based on the voltage it is seeing.

On the area close to the beginning we have Battery power 50W, SoC 79% and Voltage 53.1V

Using this chart for LFP lithium:

Looks like your BMS is correctly calculating the SOC based on voltage when current is low.

The spike upward of ~5% SOC that you are seeing seems to be caused by the battery power going up due to slight current increases (due to consumption). The BMS has to compensate for that, however that seems to be slightly off, but not by much.

Looking at how well behaved your BMS is, I don't think you will need to charge to 100% every day. Unless you see issues in the future.

Edited June 19, 20233 yr by HendrikBigChief

Thanks @HendrikBigChief, really appreciate that, especially the explanations. Puts my mind at ease.

Now I just need to get my head around how it's all wired together so I can confidently turn it all off...

On 2023/06/18 at 5:43 PM, splunker said:

• AC IN - off (cuts grid power to the 3-way Changeover switch)
• Changeover Switch to Eskom (is this the the <30ms switch?)
• AC In - back on (Grid power to Changeover

Hi Splunker

I was mentioning the <30ms because people can flip the change over switch so fast that appliances don't even reboot. But I don't think this was how the switches were designed.

I would guess that AC in supplies power to the inverter and AC out is a breaker on the output of the inverter. If this is the case then you have it wrong that those breakers have anything to do with when the CoS is on Eksdom.

On 2023/06/18 at 5:43 PM, splunker said:

• Solar DC breaker - OFF (cuts solar power off to the inverter)
• Switch off the inverter.

First switch off the inverter and check that solar power falls to 0 before switching the PV isolator.