Van theplanman

If money was not a problem i would definitely go for a stack of 4x  Pylontech US3000c or UP5000. I couldnt be happier with my 2 US3000C's just wish i had 2 more of them haha. 

That is true, but the values it sends are practically static. It sends a static 53.2V as a charge voltage (and 52.5V is a better alternative), and the charge current limit (CCL) is 25A per brick, which it lowers to 12A when it gets to 99% full. If you exceed the 12A... nothing happens. The battery is pretty forgiving about everything except voltage: If you exceed 54V, it switches off.
In other words, there is almost no difference between following the instructions of the BMS... and just setting 53.2V and a 25A (per brick) limit in your inverter config. The latter will work just as well as the former in the vast majority of cases.
It is a good thing to connect whatever means of control the BMS has, but what I mean is that the BMS should not have to send CCL=0 to tell me to stop charging, unless it's an emergency. Ideally the BMS should only send CCL=0 when it's absolutely imperative, in other words, when damage will result if I don't, and then it should activate its own self-protection if the inverter/charger does not comply.
A two-signal analog BMS can send a CCL=0 (and DCL=0, discharge current limit) just as effectively without the cost of the CAN-bus electronics.
There are many BMSes that send CCL=0 when the battery is full (and it is my opinion that they should not, they should not intervene in this way). This includes BYD B-Box pro as well as the new 24V Pylontech batteries. If you do that, you get a sawtooth voltage and SOC chart, because the charger stops charging at 100%... then starts again at 99%, causing these little micro-cycles at the top. Voltage control is better. Once you reach the target voltage, current automatically stops flowing because there is no potential difference.
So don't get me wrong, I do like the CAN-bus bmses and the communications. It is a good idea. You get SOC tracking from the horses mouth, you get information about cell temperatures, some BMSes can even tell you the bitmask of the balancer (which cells it's bleeding off), and of course it can communicate alarm conditions. But it's not like you cannot live without it.
On my system I have Victron LiFePO4 batteries with a VE.Bus BMS. This is essentially a two-signal BMS. Not a day's trouble...

Allow me to disagree, mostly because there are a LOT of systems out there that rely on a simple two-signal BMS. These are analog signals, usually dry contacts. One is closed when you want to signal the inverter/charger to stop charging. The other is closed when you want the inverter to stop discharging. The BMS also has a good old clunky contactor, or maybe a more modern FET, and that forms the last line of defence: Should you not heed its requests to stop charging or discharging, it will disconnect and leave you in the dark.
Furthermore, and here I actually have some experience, the best BMSes out there are the ones that don't apply charge current limits. There are a number of them that implement some kind of fancy "ramp" system that works well with one inverter (SMA usually), but completely sucks with another inverter. Current limits will lose PV production, because there is almost always periods of time when the MPPT could have done more if some current limiter wasn't interfering with things.
I've also done tests on batteries where we attempt to overcurrent them, either on discharge or on charge... and it takes a heck of a lot of effort. I've never managed to get one to actually switch off. We charged the living daylights out of one, raising the temperature to 42°C, and that was the worst we could do. On the Discover AES we blew the internal fuse without the BMS batting an eyelid.
It is far better to size the bank such that your PV will never exceed C/2, and set safe voltage, and then rely on dry contacts, then to deal with a fancy smanchy BMS that attempts to do current control.
The best BMS though, is the one that knows how to do voltage control. It can accommodate a low cell by lowering the charge voltage, and then adding a slight offset to facilitate balancing. Very few BMSes get this level of sophistication right. The best one I've seen is made by MGE, and the Discover AES is not bad either. For DC tied systems, you do far better by using a lower charge voltage and then ignoring the charge current control, because the most commonly used batteries (Pylontech, BYD) tend to set charge voltages that are way too high.
The way I see it, the BMS comms is makes it possible to do certain things you otherwise cannot. It adds an extra layer of protection, in the sense that high temperatures, high discharge currents, and so on can be avoided, and that can extend the battery life (but mostly... it means less warranty claims for the manufacturer). It also means the inverter can avoid a hard switch-off that might leave you in the dark. But I would not say a managed BMS is the be-all and end-all... simply because there are many many more systems out there without it, and they work just fine. If you design the system in proportion, a BMS should never have to intervene in any case.

I agree. If the inverter has the capability to communicate with the specific BMS you obviously want to make use of it. But there is a lot of inverter/Battery combination out there who can not communicate with each other at the moment. But (based on my experience) If the inverter has accurate SOC calculation and is programmed in line with the appropriate battery charge and discharge parameters the system will work well even without a direct communication link between the inverter and the battery.       

Settings depend on many factors: what sort of battery you have, how it is connected, what your preferences are (e.g. prefer longer run time during blackouts, or prefer to minimise utility energy usage), etc.
Certainly power cut-off and restart sounds bad. I think you should contact your installer in the first instance, or give us a lot more details about your system.

Even with the spec posted, he might not have the right incline angle on his roof, or Shades, or no North facing roof etc, to be able to use the full potential of the panels. Over sizing helps, especially in winter or cloudy days. So I stand by my rough estimation above and I can guarantee you that he will make use of all the nine panels 😀

An Afrikaner got stranded on a deserted island. They found him three years later. The island had received somewhat of an upgrade since he landed there... and it sported (among others) two churches. When they asked him about it, he explained that one of them is the church that he used to go to...

That rise in production is normally for short periods and its called "Cloud edge effect". It typically happens when a cloud clears before the sun and the sun breaking through the edge of the cloud, creates a very bright light. I have seen this last for up to 15 minutes on days with a thin bank of clouds where that same effect is created. 
During cloudy days you should experience high peaks, but in general the overall production for the day would be much less than on a sunny day. 
 

In terms of aging from charging and discharging, here is a nice more or less standard charge discharge curve that says it all:

What you can learn from this is, don't go below 90% DoD or 3,1V and don't go 90% SoC or 3,45. But as mentioned already balancing takes places in higher regions like 3,55 or even 3,6V so take that into account as well. Now I don't know how and at what voltage these dyness batteries balance but it is important to give them a change to do so after each let's say 10 cycles.
And also very important: Do not charge below freezing temparatures at all!

US model fits for SA 
I have bought all my Sonoffs from Banggood. With the shipping method 'South Africa Direct Mail (Tax Free)' the shipment has always arrived at my doorstep within 2 weeks (granted my last order was before Corona). And shipping costs were usually even cheaper than domestic shipping from a local supplier in SA 😶

Someone might be interested in my monitoring of my batteries : to show true batt. volts and charge/discharge current.
I use a Mooshimeter I bought on the 'net.  It can display 2 functions simultaneously : my case batt. volts and true charge/discharge current.  I connected 3 input plugs to (a) B+ terminal of Axpert, (b) B- terminal on Axpert and (c)  B-  terminal at the batteries, so creating a small volt-drop. It's then displayed in the 100mV range which is exactly proportional to the current [in both directions].  By quick calibration I measure about 5mV/A.
It's that simple and I carry my phone/display anywhere in the house.  It has logging functions I haven't mastered yet!
If someone needs help/more info, let me know.
 

Most damaging is discharging a cell below 2.8V or charging a cell above 4.2V. That instantly destroys that cell. But your BMS will guard against that.
Second is charging too hard at cold temperatures (below 1°C, but that depends on battery specs, even better to keep it above 5°C). Again, the BMS should guard against that.
Third is running the batteries at high temperatures (due to hard charging/discharging). Most smart batteries will reduce charge/discharge power when they exceed 40°C. It also follows that it is better to store them in a room that remains under 40°C, for that same reason. This does not destroy them, but does cause them to degrade faster.
Fourth, I would say, is discharging too deep. Below 10% SoC reduces cycle life significantly. Pylontech (and I suspect Dyness by extension) will stop discharge at 10% SOC in order to reach the advertised cycle life (6000?).
Fifth, keeping the batteries fully charged all the time at a very high voltage. If you cycle the batteries daily, it is fine to charge them to 53.2V as the BMS requests. If you keep them permanently charged, 52.5V is better. Assuming a 15-series setup of course. Victron systems use a lower voltage for Pylontech already (but probably not for Dyness... I don't know what it does for that one). This is probably the least damaging factor and not one to worry about too much. But it does reduce the life a little bit, just like it does with all Lithium chemistries.
Generally speaking (across all battery chemistries) slower discharge is better because it is more efficient. For lead acid batteries this is known as the Peukert effect. The harder they work, the more energy is lost in the process. BUT, with that said, Lithium batteries have almost no Peukert effect, to the extent that it is not even considered when designing. The calculated peukert constant is somewhere between 1 (ideal) and 1.05, whereas for lead acid batteries it's 1.1 to 1.2. That is to say, lithium batteries show almost no "fade" when you discharge them hard.
However... they heat up. And they don't like to get too hot. For this reason there will be healthy limits to how hard you can hit them and for how long. Generally you can discharge at C/2 for long periods with no adverse effects, but it is definitely better to remain below C/2.
The same applies to charging. You can charge at 1C or even 2C, but the battery gets hot and that can be detrimental, so generally stay below C/2.
80%. That's an opinion of course.
Depends on how the battery does balancing. Most batteries does passive balancing at the top, so they have to be charged 100% regularly. At least twice a month, preferably weekly.
If the battery has active balancing and can also balance in the middle/bottom (this is rare... it is not easy to do, and only really works at low power levels or when the battery is idle), then it should not matter if you leave it at low levels for long periods of time. I know very few batteries that have active balancers. The only one I've seen in person was the Discover AES (which is a very expensive battery).
Finally... don't go outside the warranty parameters 🙂
 

Just another thing to put things in perspective....  We (especially DIY-ers like me) tend to start small when we move into the green world, and for that we want to get the maximum for what we put in, and with time we gradually extend our systems.... I've started like that and is still busy extending...   
Here's the thing for typical town households, we end up with a inverter (R10k-40k), sustainable battery pack of R20-R100k and panels of R18k..  Within 10years, you encounter more costs on the inverter and batteries - but not really on your panels...  You see, over time the panels are the small change in the total installation.  Therefore, instead of adjusting panels, just install 3 more and you never have to touch them again! (I'm considering installing 3 more panels, but at 45deg towards West, purely to get the afternoon sun, as late as possible. My neighbour build on his property, killing my late afternoon sun....)
12Panels will take you far (I also have 12), for me now is to catch the early morning and late afternoon suns - to have a long as possible solar day.

Just another thing to put things in perspective....  We (especially DIY-ers like me) tend to start small when we move into the green world, and for that we want to get the maximum for what we put in, and with time we gradually extend our systems.... I've started like that and is still busy extending...   
Here's the thing for typical town households, we end up with a inverter (R10k-40k), sustainable battery pack of R20-R100k and panels of R18k..  Within 10years, you encounter more costs on the inverter and batteries - but not really on your panels...  You see, over time the panels are the small change in the total installation.  Therefore, instead of adjusting panels, just install 3 more and you never have to touch them again! (I'm considering installing 3 more panels, but at 45deg towards West, purely to get the afternoon sun, as late as possible. My neighbour build on his property, killing my late afternoon sun....)
12Panels will take you far (I also have 12), for me now is to catch the early morning and late afternoon suns - to have a long as possible solar day.

It depends where you live. In South East Namibia, for example, winter can be better than summer. The weather is dry (not even a wisp of a cloud, cause it's summer-rainfall area), and the temperature is cooler (PV panels don't like heat). This often makes up for the fewer daylight hours.