I84RiS

What is meant by this statement? The word "plugged" seems to tell me that your wife plugged the inverter output into one of the electrical sockets in the house while the grid supply was still present?

Set the battery to AGM V in the settings and also program the correct charge paramaters (volts and charge current). Remove the communication cable between battery and inveter and see if you can charge to full SOC. Perhaps also try a full (to about 20% SOC) discharge and charge cycle using AGM to see if it resets. Assume you have already tried to reset the battery and powered it off and on again? 55.39 volts does seem full and is about 3.45v per cell. Seeing that it is a back up system only, how often do you cycle the battery and if you do not cycle it as what SOC is it kept at (assume 100% since you have it set as lithium on the inveter). Do you have access to the cell voltages to see what is actually happening to the individual cells?

It is a 2 step process, first apply for permission to instal. 2nd apply for final approval once permissions is obtain and installation completed. Do you already have the permission to install since the system has presumably been commissioned already. Don't think you have a choice. As part of the formal approval process you will be contacted to have a new meter installed in any event so why not do it now. The meter works well and does not suffer form nuisance tripping. I have tested mine by pushing 1000watts to 1500watts back into the grid for a few seconds (when the CoCT technicians where on premises right after they installed it) and it did not trip.

If I recall correctly, Shoto uses a Pace BMS, therefore PBMS tools should work as this is the correct software to use with a Pace BMS. The issue with the software is that there are so many versions that it is impossible to keep track (some battery manufacturers even have their own branded version of PBMS tools). You will need either a USB to RS485 (with the FTDI chip) or a USB to RS232 (RJ11) cable (also with the FTDI chip). If you use the RS485 cable you need to use PBmodbustool software. If you use the RS232 cable you need to use PBMS tools software. You can try the cables without the FTDI chip but these are often a hit or mis.

Are you fully off grid? If not, then go with one larger inverter as apposed to two smaller inverters. You don't not need the redundency if you still have a utility supply. Should the inveter fail, all you need to do is switch over the change over switch and you are good to go. Things to consider if you do decide on two smaller inverter as opposed to one larger one. Paralelling inverters leads to additional complexities and ineffencies. Make very sure both are on the same firmware. Additional AC and DC wires causes additional ineffencies. Monitoring gets trickier, battery communication and set up is more complex. By adding a 2nd inverter you are doubling you likelihood of having a failure. An inveter can use anything between 75w to 100w to power itself. For 10 hours overnight that adds up to a lot. Multiply that but two if you want to paralell inverters. One larger inverter is usually more cost effecient (cheaper) compared to two smaller inverters. If you are offgrid with no utility supply it makes sense to go with 2 smaller inverters.

What was the outcome of this?

Both will work. If you choose an earth spike, make sure the earth spike is bonded to your DB (installation) earth so that there is only one earth.

It is the P16S100A (PACE) BMS? If it is, this BMS will report the battery pack with the highest SOC to the inverter while charging and the battery pack with the lowest SOC while discharging (when using comms). Unless there was a very recent change in the firmware, this BMS does not report average SOC values. When at all packs are at 100%SOC and no longer charging (at rest), are those two values (the 95% and the 87%) the same, ie does both report 100% (or 99%) SOC? Is the total available capacity correctly set up in the inverter settings (total capacity of all 7 batteries combined)? Is this a newly commissioned system? If it is first charge to 100% and let the cells balance for a few hours, then start cycling en see if the difference improves. If it is an older system, I assume you regularly charge to 100% SOC?

The CT is important for other functions as well, by example if you want to use PV to supply power to items on the non essential circuit you can do so with the CT correctly set up. Normally the items that use the most power are on the non essential circuit therefore having the ability to use PV to power these items is a major cost saver ito energy cost and getting the most out of the inverter It might be that your CT is pointing the "wrong way", but it the numbers displayed on the inverter is correct then ir is very likely that the two wires connecting the CT to the inverter have also been swapped around, so it might appear to be the wrong way around but in actual fact it is not.

Also need to consider what your local municipal requirements are for minor build work. Using brick (and I assume mortar) will likely fall into minor build work which might require some form of approval. What cooling ideas do you have in mind as well as mitigating dust ?

This might be to low to turn on the MPPT or it might drop in and out of the MPPT range as the elements (heat, clouds) impact the PV panels. If the input voltage is to low to turn on the MPPT zero curent will be produced (meaning zero watts even though there is 129v) What is the MPPT range printed on the labels on the side of the inverter? What is the panel specs (VOC, VMP etc)?

Like this, all cables should be the same length and as short as the installation allows. Fuses and cable current carrying capacity to the updated to allow for the revised charge and discharge current of the revised battery bank. Go for a busbar if you are able to avoid daisy chain as per the picture

Assume you have a sunsynk inverter? Go to the screen in the picture. Once there select and hold in the enter button for a few seconds until the DC and AC temps show in the Inverter Power block Not sure what app you are using, if you want help on this you will have to be way more specific (like the app name)

I agree with you, the numbers make no sense. I am guessing that the inverter is being fed data from the CT that it cannot correctly interpret.

You cannot trust the BMS SOC readings under these circumstances. The BMS will reset the SOC to 100% when any cell reaches the overvoltage protection as programmed in the BMS (normally 3.65v for a single cell). If you have high mV differences at the top end this usually means that the other cells are still some way off from 100% SOC (and each time this happens the discrepancy between real SOC and reported SOC increases). You want to try and get those cells all above 3500mV as a start without cell4 overvolting. Might take some time. Undervoltage protection is normally at 2750mV for any cell which you want to try and avoid.

When the battery is full or close to full and you apply a high load does the voltage of cells 7 and 8 drop more compared to the others cells? What you can try to do is to discharge the battery at a very light load so that cells 7 and 8 remain above the low voltage protection level as long as possible. Then charge up at a very low current and at a voltage lower than the manufacturer recommended absorption voltage (set float at the same voltage as absorption). You will also have to remove battery / inveter communication (if you are using it) Repeat the above cycle, each time increasing the charge and float voltage slightly (keep current low) to see if you can correct the out of balance cells. It might take a number of cycles. Had a similar issue with a pretty new battery. Using the above I managed to correct the out of balance cells, but unfortunately in my case the cells would go out of balance again after a few weeks of daily cycling. The cell was eventually found to be faulty.

This looks like an issue with the CT (or the data provided by the CT to the inverter) Where is it installed (it should be installed on the main grid incoming hot/live line before any load and the arrow on the CT should point away from grid and to the inverter) and how far is it from the inverter (more than 10 meters impacts the signal and can cause errors in the data provided by the CT to the inverter) On the system mode 2 screen, what is the inverter power limiter set to? You should select Zero Export only and deselect limit to load.

The point I was trying to make is that there were no pack overvoltage events in that log, meaning that the batteries were not charged at a to high a voltage. The only conclusion that I can come to is that battery (or a specific cell) was indeed at fault. @SteveD perhaps you should speak to Pylontec directly (or whomever holds the contract to honour this is SA) as opposed to the supplier

If you look at the event log you will notice that the there are a number of overvoltage alarms where the highest cell voltage is above 3650mV while the lowest is around 3400mV (at the same time). One should also question how the BMS allows a cell to reach 3834mV. There are also a number of items on the event log where the lowest cell voltage is around 3000mV while the highest cell voltages 3250mV (at the same time). Unfortunately the data does not indicate which cell or cells is/are overvolting Not to sure what the pack overvoltage level is on these batteries but highest pack voltage per the data was 53.295V which seems ok ? (so the overvoltage is/was not caused by a pack over voltage but rather a cell overvoltage event) My take on this data is that there is /was likely a runner cell in this pack causing the overvoltage alarms (ie there is/was one or more weaker cells compared to the others that would reach 3650mV on charge well before the other cells and 3000mV under load also well before the other cells). If you have a runner cell your charge voltage (on your inverter) really becomes irrelevant to control this (unless you charge a very low voltages). Unfortunately (for you) and fortunately (for Pylontech) you have no way to proof that this was the case from the start. But, given that there is only 391 cycles (does this look correct given the 6272 OV times) on this battery it is more likely than not that when you purchased this batery that this was indeed the case. I think they are taking you for a ride and hiding behind their T&C. Unfortunately runner cell are part and parcel of pre packaged battery packs with integrated BMSes and should actually be treated as latent defects.

It should be as simple as adding the 3rd so that all 3 are connected in parallel. BUT, you need to consider if battery cables are still correctly rated and capable to carry the revised maximum current (which in now higher), same with fuses and breakers which needs to be assessed for correct rating given the new maximum current that the batteries will be able to provide. The cable is not your standard LAN cable, you should however get the correct cable, which supports communication between the batteries, with the new battery.

As suggested above, try a restart. If that does not work you likely have a blown/broken PCB board. Try switching off gridd supply, if the inverter then (starts to) supply load using PV or Battery it is likely to be a broken PCB.

I would remove the BMS communication and use/test using AGM setting or something similar (set up the charge voltage and current using battery manufacturer recommendations) Unfortunately you would then have to keep an eye on the battery to keeping track of those cells voltages and sudden changes in the SOC led indicators to see if the issue reoccurring. Also check what happens to those voltage readings when under low, medium and high load. Do they uniformly drop when the increased load is introduced and then uniformly increase when load is reduced again?

I assume the battery switch turns off the BMS which shuts down the battery as opposed to it being a switch that disconnects the current by introducing a break in the cable. If the switch did the latter the battery would remain on as it can power itself. My batteries do not have on/off switches, so not to sure

Are those volt readings at resting or under load?

A lot to comments on in this graph, that sudden increase and then the immediate decrease at 2am is odd (potentially pointing to cell imbalances) Then at about 9 am, just as the battery is starting to charge at higher amps (presumably PV picking up?) there is a sudden 20% odd jump in the SOC (also pointing to cell imbalances, the movement seems to correlate in magnitute to the movement at 2am) If I had to venture a guess, the SOC readings are probably incorrect and not correlated to the actual cell voltages of the individual cells (or perhaps one of the cells is not balanced to the rest of the cells). So when the SOC drops to 1% it is likely that the battery is indeed flat (or at least one cell has reached the low Volt cut off) which then forces a recharge, cycle then repeats it self every x days. My guess is the cell imbalances means that the battery never really reaches 100% SOC, it only reports 100% SOC as one cell has likely reached the overvoltage level (while the rest of the cells are likely at a lower SOC level). As soon as a cell overvolts the BMS will report that the battery is at 100% SOC while the true SOC gradually drops over a few days until the battery is flat. To determine what is going on here you need access to the individual cell voltages. A lot of guess work in here, take it with a pinch of salt. If you do get to the answer, please post it here would like to see how far of the mark my guess is.