flyfisherman

i used to do this when wanting to read the battery info but it was too much hassle. perhaps if you buy the splitter it could work? I Dunno. I jsut left it as i now and just use the inverter battery readings

If you do that, it would be using the inverter in voltage mode basically. Not recommended when you have the facility of using SoC which is much more accurate. Voltage won't be accurate for switching back to grid power etc based on the SoC like the timer does. 
The inverter does pick up most of the battery info though, not the cycles etc, but what its needs, it picks up. 
 
Perhaps from time to time when you want to see the detailed info u could connect the battery to the pi directly and check. Looks like you Would have to disconnect it from the inverter, make sure the setting BMS_err_stop is disabled then otherwise your inverter will cut power. 

This isn't a sunsynk / deye inverter from the looks of it (see device mode) , so don't expect to get this @flyfisherman. I would rely on what solar assistant themselves are saying. 

The screen you see on LiBMS 03 is the correct one. The one showing all that extra detail is not for Lithium batteries with comms. You won't be able to see individual battery or cell info just from the inverter. Adding something like Solar assistant with the relevant battery cables will help. 
Are your 2batteries connected with a comms cable as well? If so then the BMS knows about them both. BMS will manage the charge and discharge amps based on variables incl load, temp, SOC etc based on the max values you have set (for both grid and PV) 

Based on the settings I use after much research about this topic (THANKS ANDY and some others)
Optimal charge/discharge rate for lifepo4 is 0.2C that combined with the correct top end voltage will give maximum life for the batteries.
If your BMS balance start voltage allows it then try keeping the voltages to max of 3.45v per cell. Note: some/many of these prebuilt batteries have a higher balance start voltage so you would need to adjust the upper voltage accordingly or adjust the BMS settings to allow balance start at a lower voltage.
Most households using 2X 48V 100AH batteries will only occasionally go above 0.2C like when the kettle, geyser or microwave run, and then usually only for a few minutes at a time and mostly only when solar is not not available to support the loads, nothing wrong with that.
As for DOD try never going below 20%, that bottom end is where a lot of the "wear and tear damage" happens.

My total electricity bill is around R800-R1000 per month prepaid - use one of those funny plug-into-the-socket type chargers to charge with electricity directly from eskom - no pre-paid meter or anything at my house...
This is including my pool pump running 3 hrs in AM and 3 hrs in PM as well as a geyser running not on a timer.
The rest of the time the house is idling as everything is energy saver ++ kinda ratings.
I don't mind buying power from the grid at all, but I think according to my rudimentary calculations 8x 455W panels, 2x 5kwh batteries and a 5kw inverter should take me pretty close to off grid, at least in the daytime, but maybe not all the way. I am OK with this and might even prefer to buy power from grid at night in favor of cycling batteries, and only use battery at night during load shedding, although my house uses hardly anything at night so might as well run it off batteries at night too?
 
I think I have settled on 8x panels in series into 1 MPPT...this is called 8S in solar terms i think?
 
I do have one more question  I did some calculations based on zero-degree Celsius days in Riebeek Kasteel (little dorpie in western cape)...then the Voc can apparently be like 54,55V per panel based on stc? So, am I correct in saying 8x55=440V worst case is ok as it's under the inverter 500V limit and when operating even in cold then the Vmpx8 will be like roughly 8x46=368 so that is all still perfect and does not overload the inverter or MPPT even in icy cold days? Warm days is not a problem it wont blow up anything as voltage drops 
 
Thanks again for all the input - completely wasted 2 days at work reading about solar and inverters and doing some calculations and hardly did any work 🤣 And I have not even connected the app or remote monitoring yet ... I dread that day as I can see how it can become rather addictive

Due to the marginal difference in a lot of cases between 4S per MPPT and 8S for the Cape 8S is by far the better option due to the winter period. 
Little info makes a huge difference 😅

Run off of batteries the whole night so you can store and use more PV during the day. This will save you a lot more money on electricity. Use the grid only when you really have to. 
I think of Eskom as my generator for occasional use only. It's still cheaper to charge batteries from Eskom than it is from a generator. 

My total electricity bill is around R800-R1000 per month prepaid - use one of those funny plug-into-the-socket type chargers to charge with electricity directly from eskom - no pre-paid meter or anything at my house...
This is including my pool pump running 3 hrs in AM and 3 hrs in PM as well as a geyser running not on a timer.
The rest of the time the house is idling as everything is energy saver ++ kinda ratings.
I don't mind buying power from the grid at all, but I think according to my rudimentary calculations 8x 455W panels, 2x 5kwh batteries and a 5kw inverter should take me pretty close to off grid, at least in the daytime, but maybe not all the way. I am OK with this and might even prefer to buy power from grid at night in favor of cycling batteries, and only use battery at night during load shedding, although my house uses hardly anything at night so might as well run it off batteries at night too?
 
I think I have settled on 8x panels in series into 1 MPPT...this is called 8S in solar terms i think?
 
I do have one more question  I did some calculations based on zero-degree Celsius days in Riebeek Kasteel (little dorpie in western cape)...then the Voc can apparently be like 54,55V per panel based on stc? So, am I correct in saying 8x55=440V worst case is ok as it's under the inverter 500V limit and when operating even in cold then the Vmpx8 will be like roughly 8x46=368 so that is all still perfect and does not overload the inverter or MPPT even in icy cold days? Warm days is not a problem it wont blow up anything as voltage drops 
 
Thanks again for all the input - completely wasted 2 days at work reading about solar and inverters and doing some calculations and hardly did any work 🤣 And I have not even connected the app or remote monitoring yet ... I dread that day as I can see how it can become rather addictive

Yea that would struggle lol . The absolute most i would go safely is 9 panels per string 455wx9 so about 4,1kw . The JA 540w panels can also work but you will experience some clipping, so 9x540w =4,86Kw on a string in theory. I would not go larger than 455W canadian panels on the 5kw Sunsynk/deye inverter as they are very amp heavy panels and overshoot their specsheet numbers by a fair margin.

It won't be easy to connect up to 6.5kw per MPPT and stay within the voltage levels. 

I also run 8 panels per string and it works wonderfully. I started with 5 panels per MPPT and could see a noticeable wattage per panel increase from the higher voltage of 8 panels . These inverters really like high voltage strings for maximum efficiency .

I also suggest 1 string with all 8 panels. It's simpler wiring, and it leaves an MPPT open for future expansion.
What you lose in redundancy on the panels, you gain in redundancy on the inverter. It's much more likely an MPPT will give up the ghost, and then you can just switch over to the other one if you can't send the inverter in for repairs.
Also, I honestly don't see the benefit of having redundancy in having multiple PV strings as you explained. If one panel breaks due to hail or whatever, then you simply plug it out, and connect the two panels either side of the impacted one together. Going from 8 panels to 7 is still fine for the inverter. Going from 4 to 3 is not. So you will essentially lose an entire string if you only have 4 per string, and one panel fails. Also, panels remain functional even after hail damage. They usually have junction/diode boxes on the back that can essentially short out an entire section of the panel that's damaged. So if one section get smashed, 60% of the panel remains functional. 
The only case where you should split your panels, is if you are unable to put all 8 of them on the same roof, looking in the same direction. You MUST split to separate MPPTs if you have one batch facing north and another east/west. If the fit is tight, see if it's possible to fit all 8, even if you need to have some overhang here or there. 
For my installation I initially planned to go 6 north and 6 east. Then the installer managed to fit 10 on my north roof. 10 panels facing north will give you better yield than 6 east and 6 north. 
To answer your last question, about the 6.5kW max rating. Nobody has been able to give me that answer. I interpret it as 6.5kW overall, split whichever way between the MPPTs. So you can in theory have 6.5kW PER MPPT, but you will only ever get 6.5kW out of your PV as a whole. This helps to greatly increase your "solar day", but it's a waste in SA as we have tons of sun here. Overspeccing is great for the maybe 30 days of crap weather we have. Rest of the time those panels are just going to sit and bake in the sun and do nothing.

I also say 1 string of 8 facing the same direction. 
I know you say you are a low electricity user but you going to see how on cloudy days that you are going to want more than 8 panels so keep 1 mppt open. 

When you have no panels, its ideal to keep your batteries full not to cycle them. I would set the time of use to 100% so the batteries stay full waiting for load shedding. When  panels are installed then you can cycle your batteries to a certain percentage and leave enough energy to push through load shedding. Discharging them to 60% is not bad

6500w is max for the inverter as a whole. Just note its the max DC the inverter will take either to charge batteries or power loads or a combo. You can have more than 6500w (to a point) as long s you do not go over the V max per mppt. This is beneficial in winter / cloudy days but you waste production in summer 
I would advocate 1 string of 8 panels on 1 mppt - then add more to the 2nd mppt when you can

Thans again to everyone for their valuable advice over the last couple of days on the two threads I posted. I know exponentially more about the system I have installed now from your feedback and other threads on here. Much appreciated. Realy.
Just makes me wonder why installers, who are highly recommended etc. and have all the certifications etc do things in certain ways and not according to manufacturer spec. This particular installer, when asked about why the batteries don't charge to 100%, said "ah these Dyness sometimes go to 90% and sometimes to 80%, its just the way they are made" .... something we have determined is clearly not the case, but rather was the settings on the inverter.
Anyways, thanks again for all the advice and input. I think just to be safe, I will get them to come re-wire as per Dyness manual/spec, just to hopefully cover my own arse should there be a warrantee claim one day because Dyness seem to require pictures of the wiring for warrantee registration.

That would work fine if you need to point the 2 strings in different directions, like mine facing east and west.
Yes, if the panels facing same direction this would be the the better option.
 
If you can afford it and safely oversize the panels (amps/volts in spec) then that will be good for winter production.

Thans again to everyone for their valuable advice over the last couple of days on the two threads I posted. I know exponentially more about the system I have installed now from your feedback and other threads on here. Much appreciated. Realy.
Just makes me wonder why installers, who are highly recommended etc. and have all the certifications etc do things in certain ways and not according to manufacturer spec. This particular installer, when asked about why the batteries don't charge to 100%, said "ah these Dyness sometimes go to 90% and sometimes to 80%, its just the way they are made" .... something we have determined is clearly not the case, but rather was the settings on the inverter.
Anyways, thanks again for all the advice and input. I think just to be safe, I will get them to come re-wire as per Dyness manual/spec, just to hopefully cover my own arse should there be a warrantee claim one day because Dyness seem to require pictures of the wiring for warrantee registration.

Well, one can exaggerate everything. Who wants to charge with 1C? I set my inverter to charge from utility with 0.1C to preserve battery life. PVs charge at rare peaks 0.2C for short times. That's 80A on 25mm² cable, capable of 160A continuously. My inverters have total 10kW max power. The cooks very rarely manage to pull 8kW for short moments. That's 160A or 0.4C on the batteries if nothing is coming from PVs. Most of the time the load runs between 350W and 3.5kW.

100% my feeling as well but not what the clever people want us to belief. 
Just look at house wiring where the N is much shorter than the L going down to light switches and back and all circuits and equipment function correctly. AC has nothing to do with it functioning correctly. The load just gets a voltage to do the work needed. 
We do however try to give each battery as close as we can the same voltage to charge and to discharge. It is the run between battery and inverter we want to keep as short as practical possible but need not be measured to the mm/cm the same length.

That's what is my opinion. And it is also my experience that unequal recharging of packs due to such difference is automatically equalized when they reach full charge. Provided that the BMS do not intervene with false information to the inverter.

As stated in the video on large banks with a lot of batteries it is a problem. When only using 2 it is still great to keep both the leads of the same length. 
When looking at his video one will see the 3 or more banks also have different lengths of cable. Further by having fuses in only the positive lead the fuse resistance can be as high as 8m cable. Thus his positive cables have a resistance much higher than the negative. We just don't see the extra resistance. 
A great video to indicate how one applies over current protection to each battery and not the common reason mostly given that you add fuses to protect only the cable to prevent a fire. 

You definitely want it like the manual is showing. Currently your one battery will put in much more work and it gets worse the more batteries you have and the larger currents you pull.  Eventually they get very unbalanced . Will Prowse did a video about that a while back . https://youtu.be/oXBT8lSC25M
 

It is seen as the total length of cable. If you look at the picture in your post the left side as per manual is the better way by a very small margin. 
Your install the battery on the right has longer cables than the one on the left as power goes from inverter to the 1st battery and only then to the 2nd battery. Thus 2nd battery will do less work and take a bit longer to charge. Having only 2 batteries it is not a train smash. The 2nd one will catch up when charging and also discharge well. 
This is like so many things in solar we always want the BEST of everything. 😀😀