Hi
I have a new solar installation installed this week by a 3rd party. Their support is very slow so I was hoping to get some input from you.

I hope you can be patient with me, as I am very new to this.

- Sunsynk Hybrid Auto inverter
- Synsynk 5.12KWh battery
- 4KW of panels

Everything seemed to work fine for the first 36 hours. The battery discharged to 20% overnight, then grid power was used until the sun came up. All good.

But last night the battery discharge was unusual. When the battery reached around 57% / below 50V, the inverter drew from the grid to recharge the battery.

This is now happening repeatedly every time this 57%/50V threshold is crossed.

The battery is not set to "grid charge"

Can you advise what is going on?

You would have to have grid charge ticked under the 2nd battery tab, I'd imagine and under time of use, you would also need some setting ticked, with 57% as the charge level in there somewhere... you'd have to look on the inverter and maybe take a photo or 2 and lets see what setting you have and what they would imply...

Edited August 11, 20223 yr by Kalahari Meerkat

Wow thanks for your quick reply. I will grab the settings and post them when I can.

But my thinking was:

-the system was working as expected on "Day 1" (Top left screenshot) - i.e. battery discharges all the way to 20%

-on Day 2, the battery will not discharge past 57%  (Top middle screenshot)

So that would imply a setting was changed? But nothing has changed.

Thanks again - I'm hopeful we can work this out with you help. I will post the screenshots when I get back.

 

Edited August 11, 20223 yr by tsf
typo

7 minutes ago, tsf said:

So that would imply a setting was changed? But nothing has changed.

That is strange, but without seeing what is there its difficult to figure out why it's doing what it's doing. Looking the 1st set of images above, it seems to not actually grid charge, but just switch to grid and let the battery sit at 57-odd %.

So, you probably have grid charge un-ticked on the 2nd battery tab, but on the time of use tab, presumably have a 57% or whatever it is value in there, with a tick to go to grid, once this level of dis-charge is reached...

 

Show a Custom graph of your batteries' V-Bat and V-BMS parameters at the same time?

@tsf

From the outside, it looks like you do have a few anomelies:

• not enough PV - it takes from 08h30 to 16h30, and your batteries don't even get to 100%. Assumtion is that the Battery charging rate is suffieceint - at least C/2 
• not enough battery capacity. Not sure if you also suffer from "loadshedding" but I'm assuming you are in the northern hemisphere, as your sun seems to be very late (08h30-20h00), so you have very little battery left for emergencies
• on 10-08-2022, at around 21h30, your house started pulling short 2kW of load every couple of 10 minutes or so. This continued till the next morning at 08h30. What is the nature of this load, as this should not be "normal" loads, You should just see your "base" load, i.e. when your house is in "rest" overnight and everybody is asleep!
• In order to control the battery, you nood to activate "Use Timer" mode, and configure they % SOC you wish to let your battery drain to together with the time when that should happen.
• For obvious reasons, you should try and move your heavy loads to sunshine hours. Once you get the nack of that, it's easy to maintain, but it does require someone at home most of the time, as modern appliences still are relative "dumb" devices. like washing machine & dish washer.

I hope this helps somewhat, as I would not be happy with this behaviour.

Quote

on 10-08-2022, at around 21h30, your house started pulling short 2kW of load every couple of 10 minutes or so. This continued till the next morning at 08h30. What is the nature of this load, as this should not be "normal" loads, You should just see your "base" load, i.e. when your house is in "rest" overnight and everybody is asleep!

Yes - this is the core of the issue. This 2kW is not load, it is the inverter intermittently pulling from the grid to recharge the battery. Even though I do not have grid charge active. It seems to happen when battery voltage drops below 50V.

Here is the diary of activity so far:

Day 1: battery fully drained as expected to 20% (51V) overnight. Then grid was used to power the small overnight load. - (as expected)

Day 2: battery only drained to 57% (50V), and then the inverter started pulling intermittently from the grid to keep the battery marginally above 57%(50V)  - (not expected)

Day 3: battery fully drained as expected to 20% (51V) overnight. Then grid was used to power the small overnight load. - (as expected)

Day 4: battery only drained to 44% (50V), and then the inverter started pulling intermittently from the grid to keep the battery marginally above 44%(50V) - (not expected)

Last night's charts attached.

Battery settings attached.

My thoughts:

1.There is not enough overnight load to justify the draw from the grid.

2.The only "constant" I can see from the last 4 days is the grid kicks in when battery voltage drops below 50V.

Ultimately my question can be summarised as:

Why is the grid kicking in overnight, before the battery has discharged to it's 20% minimum?

 

On 2022/08/11 at 1:13 PM, YellowTapemeasure said:

Show a Custom graph of your batteries' V-Bat and V-BMS parameters at the same time?

How do I do this on the mobile app?

 

 

 

 

Are you on the latest SunSynk firmware?

"Gen Signal" and "Grid Signal" should not be ticked, since it seems you don't use that anyway and very few do. (I don't think these have any effect on your problem, though.)

The "Use Timer" should be unticked, since you don't use any of the timer entries...

The "Activate" entry should also be unticked, this is where a battery has sat, unused for a long-ish period and the Voltage is lower than it should be... this will then gently bring the battery up to charge etc. apparently.

So, no settings in there explain what your end is doing, it seems either the inveter has lost its marbles or the battey is playing silly buggers, my money's on the inverter... I don't know the Sunsynk battery, is this a 15 Cell or 16 Cell, presumably LiFePO4?

Based on my interaction with Sunsynk in the past (18 months ago) and recently (this week), I would not recommend this kit anymore to anyone, Sunsynk seem to be uncommunicative and of they do communicate the don't answer any of the queries posed. Which means either 1. they don't know their own product any better than the average Joe out there or 2. they couldn't care less supporting their items, after all, you already bought it, sucker! ... Can't think of a reasonable option that fits otherwise.

Sorry I can't really help, you could still post a photo of the LiBMS tab, but I doubt there would be anything on there that would shed light on your problem....

3 hours ago, PowerUser said:

Are you on the latest SunSynk firmware?

How can you tell? My firmware is COMM:e424 - MCU:2374

1 hour ago, tsf said:

How can you tell? My firmware is COMM:e424 - MCU:2374

MCU 2374 or 3374?
 

3374 is the latest. 

23 hours ago, tsf said:

How do I do this on the mobile app?

Is that all you have? Is is far better to use a browser on a PC, everything is a lot bigger and clearer. But if you insist on using a tiny screen, then from the "Overview" screen, hit "Equipment" at the bottom, select your inverter, you will then have various options on the top (Output, Input, Battery, Grid etc), scroll left until you see "Custom" and select it, then hit "Parameter Selection" and select V-bat and V-BMS.

 

19 hours ago, tsf said:

How can you tell? My firmware is COMM:e424 - MCU:2374

Do the procedure as above, but instead of hitting "Custom", hit "Detail". Under "Profile" you will get "Software Ver". There will be 3 values: M,  S,  and C.

M is Master MCU software version

S is Slave MCU software version

C is Communication MCU software version

 

Edited August 14, 20223 yr by YellowTapemeasure

Seems like it’s a communication issue between the battery and the inverter. 
 

You definitely want “use timer” ticked if you want to use the battery at night as you described. 
 

Switch the inverter off and thereafter do a battery reset and see if that helps. 

10 hours ago, Leshen said:

Switch the inverter off and thereafter do a battery reset and see if that helps. 

Thanks. How do I do a "battery reset"?

I am in a slightly tricky situation where, at this initial investigation stage, I do not really want to interfere with the hardware, or even the settings. Unless there is a "slam dunk" settings change that we can identify that will almost certainly fix the issue. This is because I am holding out hope that the installer will help at some point, and I do not want the installer to claim that something I did could have contributed to the situation.

 

Can I ask again about the "50 volts" battery threshold that I am observing? Can this be a factor? All of the problems seem to start when the battery drops below 50 volts. In the first few days, this correlated to a SoC of 44% or 57%. Last night, it correlated to 97%. So last night the battery was recharged by the grid in a repeating cycle from 97% to 99%, all night. Every 10 minutes.

Is 50 volts normal operating voltage?, or could something in the inverter/BMS assume this is a warning threshold and the battery needs some sort of jolt form the grid to "correct" it's voltage. (Sorry for the newbie theory)

According to this page your battery consists of 16 CATL 100Ah LiFePO4 cells. The Voltage range for LiFePO4 cells is from totally discharged at 2.5V to fully charged at 3.6V app. you probably want to keep from 2.9V on the bottom end to 3.45V on the top end, maybe... either way fully charged and at rest the cells should be around 3.4V or so and nominal is usually quoted at 3.2V, which will give you 16 cells times 3.2V being the 51.2V nominal. To have a fully charged battery it should measure 16 cells times 3.4V = 54.4V app. once it has been charged and after and hour or so at rest (no more current in or out for an hour). The SOC is very difficult to tie in with Voltage since the discharge/charge curves on the LiFePO4's is pretty flat once you reach 10-15 SOC up to 90-95% SOC.

Let me add, 50 Volt I would consider as being a pretty much flat/discharged battery... that would be app. 3.1V per cell.

Edited August 15, 20223 yr by Kalahari Meerkat

I have a possible lead regarding my problem with the battery constantly recharging from the grid in a constantly repeating cycle every 10 mins.

"Force Charge" Request

I have been looking more at the BMS screen on the inverter.

It seems that there is a threshold of 49 Volts, below which the inverter will perform a "Request Force Charge" and raise an alarm "0x03".

Please see the attached pictures. You can see that a "Force Charge" request was placed by the BMS when the battery dropped below 49 Volts. Even though the SOC was 79%.

 

Can anybody explain the purpose of this feature.. and what is the implication. Does it mean my battery is broke / has low voltage? You can see the voltage is low even though the SOC is high.

 

 

 

 

 

 

4 hours ago, tsf said:

I have a possible lead regarding my problem with the battery constantly recharging from the grid in a constantly repeating cycle every 10 mins.

"Force Charge" Request

I have been looking more at the BMS screen on the inverter.

It seems that there is a threshold of 49 Volts, below which the inverter will perform a "Request Force Charge" and raise an alarm "0x03".

Please see the attached pictures. You can see that a "Force Charge" request was placed by the BMS when the battery dropped below 49 Volts. Even though the SOC was 79%.

 

Can anybody explain the purpose of this feature.. and what is the implication. Does it mean my battery is broke / has low voltage? You can see the voltage is low even though the SOC is high.

 

 

 

 

 

 

The Pylontech US3000 BMS does the same, it requests a Force Charge to the inverter in order to protect the battery under low SOC (usually under 20%).