Nexuss

I recently saw a video going though a study they did on LFP cells and it was quite informative , among one of the important points was that cycling from 75-100% caused the most cell degradation. Cycling at a lower SOC range, like 0-60%, resulted in less degradation. Cycling from 0-100% is better for the battery than 75-100% which most people probably wouldn't expect. Here is the study and video : https://iopscience.iop.org/article/10.1149/1945-7111/ad6cbd/pdf https://youtu.be/w1zKfIQUQ-s

The "power" column in the system work mode 1. This will set charging and discharging watts. i set mine to 1000w through the night to prevent draining the battery quickly by larger loads.

4 hours ! that's very long , what is your charging current like? if there is plenty of solar available that is not normal. Paste the history log here so we can check it ,erase serial number for internet weirdos . Also check the firmware version on each battery they should all be the same version ideally. Might be worth upgrading them all .

Seems like that was already confirmed.

If this geyser still uses grid /like in winter it would be useful to untick "limit to load" to be able to supply it with solar power as well. Also just so you know the "grid signal" and "grid charge" functions on the battery setup page needs to be ticked for grid charging to work if you ever want to do that(in work mode you set the time slots which you want grid charging for). I would recommend ticking both so the battery has access to grid charging very low SOC like below 5% the BMS can then request a force charge automatically if that ever happens.

You wont see the CT coil in the flow diagram when "limit to load" is ticked, Since you have everything on the load side of the inverter you can leave it as is. Only thing i would change is the grid tricle feed to 0 watts and on the work mode screen set the SOC much lower . As it is now you will only use 20% of the battery, unless there is a grid failure/loadshedding. I would set them all at 40% as previously mentioned. I have mine set to gradually go down to 10% to get maximum battery utilization. Also tick "Priority load" so the load is priority above battery (battery wil charge with the solar thats left after servicing the load) . Currently it will charge battery first meaning you will use grid till you reach the set SOC in work mode timer.

BMS comms looks good and is working fine , all 4 batteries are there if you look at the discharge current limit ..Your charge voltage is high but i dont think you can do anything about that , i am unfamiliar with your batteries/firmware, might look into using voltage mode instead of BMS comms. Regarding the dip switch settings ,refer to the battery manual. The next screen shows that you have no non essential ? do you have your entire house connected on the load/ups side of the inverter ?

That is not what the "activate" function does... "The "Activate" function (often a checkbox) in the battery setup page of a Sunsynk (also stylized as SunSynk) hybrid inverter is primarily used with lithium battery configurations . It helps recover or "wake up" a lithium battery that has become over-discharged. In such cases, the battery's built-in Battery Management System (BMS) shuts down the battery for protection, preventing it from charging or discharging normally .Enabling "Activate" forces the inverter to provide a low-current charge (from solar panels or the grid) to the battery, even when the BMS is in a protected/shutdown state. This slowly reactivates the battery and allows normal operation to resume." From Sunsynk website.

You can get a new US3000C for R 13,282.50 from powerforum store , you wil have to come down lots on that price for the 5 year old batteries IMO.

On the battery setup , the charging amps is set way too low for your massive battery bank, this is what is causing you to lose out on power , i would set the charge current at 100-120A . Next on the system mode screen tick use timer and set the soc on 40% for all lines . This will make sure you actually use your batteries. Also tick "signal island mode" to make sure it does the N-E bonding if there is no hard bond . It does not seem like he installer was familiar with this inverter so i would make sure the CT coil placement is correct and also the settings on the second work mode screen so you are feeding back to non essentials if there are any . Give some pictures from the other work mode screen and the Li BMS screen please. Also post a graph of both solar stings voltage through a typical day , 4 panels might be too little voltage to keep the MPPT running properly so that could also make you lose power.

Yes your LiBMS screen indicates your comms is working so the float voltage and other voltages on that settings page does nothing(only the charge and discharge amps is what u can/should set). You as the end user can not change the charge voltage unless you disable comms and switch to voltage mode , or install the newest firmware which limits charge voltage (this should not be needed usually). You as the end user did nothing wrong is what i am saying . Somewhere between the inverter and batteries there is a fault causing the charge voltage to go too high. This seems like it could have something to do with the problem , i would go back to Segen and provide logs to them , battery 2 needs to be swapped or have that cell 13 replaced and they all need a firmware update for lower charge voltage. Initial looks at the other packs history does not indicate any other weak cells but i am still going though them all . Can you post some historical graphs from solar assistant for battery voltage /BMS voltage? would like to see what the inverter is recording voltage wise daily. I also notice the logs only provide data for this year ? Seems like Segen deleted the old data which is not ideal. edit * just remembered the history is cleared with firmware updates .

haha ok i admit i did not look at the other batteries and add up the voltages i apologize for missing that ! I only looked at the history data of pack 2, from the picture he posted in post nr one the voltages of the packs are as follows: Battery 1: 54.196 V Battery 2: 52.87 V Battery 3: 53.972 V Battery 4: 54.118 V Very high indeed .... lets see what the other packs history shows if their cells are more balanced . Pack 2 being lower voltage and the rest that high is certainly interesting. i would keep a close eye on that to make sure they dont go that high again , maybe even disable comms and use voltages if necessary. flashing the new firmware for lower charging voltage could be helpful i agree ,just doesnt make sense why it would go this high in the first place .

The highest pack voltage recorded across all provided logs is 53631 mV (53.631 V) Well below 54V max and the exact same value mine goes to and many thousands of other people using Sunsynks/pylontech. Here is a more concise version as it seems you are having trouble understanding what the issue is. Pylontech US3000C Diagnosis Issue: Severe cell imbalance — cell 13 has significantly lower effective capacity (~30–50% less than others). On charge: Cell 13 rises fastest → triggers OV protection early (pulsing/throttling, high OV counters). On discharge: Cell 13 drops fastest → limits usable capacity (pack hits ~6% while others ~78–91%). At sustained 100%: Passive balancing partially masks it (smaller delta, other cells appear high). Cause: Common degradation in these packs after cycles/partial charging; weak passive balancer can't fully correct large mismatch. Current Impact: Reduced real-world Ah, frequent protections, but pack still functional/safe (SOH 93%, no faults). Recommendations Immediate: Avoid discharge below 20–30% SOC. Slow charge to 100% and hold (float ~53.4–53.6V) for days/weeks. Best fix: Install a dedicated active balancer (strongest community solution): Servtec 1A (plug-and-play retrofit for US3000C) — highly recommended. Alternatives: Heltec/JK 5–8A capacitive (wired to cell taps). Long-term: Contact Pylontech for warranty/service if possible. Regular full charges for prevention. This resolves/manages the issue for most users without replacement.

The whole reason it is showing all those HV events is because of the weak cell 13 . He as a end user followed normal use procedure with BMS comms working and amps even limited to 90A so there is absolutely no reason they should not honor the warranty . The logs prove it , dropping from 90% to 6% indicated a clear problem and upon investigation the problem was found , it has nothing to do with having the latest firmware or incorrect charge voltage . Feed those logs into AI for yourself and verify if you want . @JuliusK paste the logs for the other 3 batteries as well .

No problem glad to help! it seems like that cell 13 was weak from the start with that amount of HV errors ... hopefully they honor the warranty . Its also worthwhile to download the logs from the other packs to make sure they are fine . If they wont honor the warranty installing an active balancer could maybe solve the issue, depending on how weak that cell is .