Leondavibe

i see it the other way round
ie the hybrid inverters you can set and forget and it will blend eskom and solar when battery hits x SOC you have set
while the off-grid  axpert types means you have to play around with switching UTI/SBU since only some can blend 
 
unless you have enough battery power to essentially go mostly of grid, which is often not the case ie those going for the cheaper axpert options tend to have lower battery capacity
Solarassistant can help make it a set and forget, then it will command the inverter to switch back and forth as needed, solar assistant allows you to pull data from axpeert types into homeassistant and can also give commands on certain things to the inverter via solarassistant pi
 
allowing remote management , and the data is realtime not the crap of 5min with sunsynk or other cloud setups
if/when i buy a sunsynk i would still do the pi realtime data route 

Using a chart like this on lifepo4 is folly it is almost impossible to determine SOC from voltage if the battery isn't at either side of the flat voltage curve, ie when it hits the spike up at the top when full or the knee at the bottom when basically empty
People try to recreate a chart , that worked on batteries with steep discharge curves for a lifepo4  it is a joke
 
 
If you hit full voltage it is normal for the amps to drop, the charger will charge max amps until voltage is hit then Limit the voltage and charge slower rate until the charge amps drops to a certain % of charge rate the y is garded as full and switches to float mode
Some inverters on USE/Li settings doesn't apply a float voltage  it use the float voltage as a trigger only
 
My one inverter works like this, it will charge , change to float mode ie apply no voltage and let the battery come to a rest voltage and once the voltage drops x amount under set float voltage it would trigger a charge cycle again, so setting a high float would see that inverter charge leave battery to settle to rest voltage once it triggers it would charge again
Setting the float lower allowed the battery to rest until next shedding (battery backup only had no panels at the time)
 
Instead of repeating this loop
 
The charts are useless
Resting/float approx 26.8v is full
 
ie 
My system is 48v i will charge to 53.9v  and my battery will come to rest at about 50.5
The voltage can shift a bit if moving from charge/discharge/charge again
Both those voltages are full
All you explain sounds normal for a lifepo4 battery
 
So as an example look at battery soc chart when resting full voltage, then simulate shedding  switch of mains look at chart, then switch power back on look at chart again compare  voltages 
 
Now did your battery truly discharge 20% and charge 20% in a blink of an eye, probably not, that should highlight how much a joke the charts is

Hi ,
 
First post here. I have recently had a system installed at my house. Nothing fancy but something to allow me to work when we have no power. So far the system does what I need but I have a question on configuration.
I have 2 major options when configuration the inverter.
Output source priority selection
1. SbU. Solar energy provides power to the loads as first priority. Solar and battery will provide power to the load. When the batter drops below a configured voltage it will switch to grid.
2. Uti. Solar use used when the grid is not available. Grid charges the battery.
Using the SbU mode:
The problem with this and I found it out the other day. During the day it worked perfectly. We hit 7pm Sun was gone and the battery started to get used. At 8am load shedding hit and by that stage the battery was around 20%. The utility would only charge once the voltage was low enough on the batteries. What happened though was the battery hit 10% during load shedding and then the utility was not able to charge the batteries and we had to wait for load shedding to finish.
Using Uti mode:
This works fine. I have configured the inverter to charge the batteries with solar however, if there is excess solar the inverter still uses utility to power the load. The only time solar is used is when there is no Utility power available.
I did some tests and set the voltage on the battery in the inverter to not go below 26.5V so the SbU mode works and then if the battery goes below 26.5V Utility power kicks in to charge it and serve the current load. During the day the battery and load are both served from the Solar power.
Does anyone know of a better way if possible to do this.
I am using a MUST Inverter PV1800 3kw
 

Some of these active balancers have place for a switch and it is just shorted on the board
 
Putting a switch on it and leave the active balancer inside the battery and just have a switch to enable active  balancer from time to time when in the steep section of the soc graph not all the time
I have a shoto server rack battery  with one bad cell that always drifts 
I soldered two wires to this cell routed through a hole to the outside of my case to a quick connector
 
When this cell has drifted i manipulate this cell by connecting a charger to this quick connector or add resistance if i overshoot the charge

Since you have active balancers , you don't need to buy a power supply
 
Whenever you are home while battery is fully charged just lift the float voltage to sustain the voltage at 3.65v per cell and switch on the active balancer
 
When load shedding switch it off
 
Then when fully charged switch on the active balancers again
 
Just don't leave them on all the time
 
As they may move power around in the flat portion incorrectly ie do work it has to reverse again when full
 
All you want is to be balanced at 3.65v ie all cells has to be 3.65v at the same time
 

Active balancing only works above 3.4V. You can try by starting balancing at 3.45 and charge to 3.5 and try hold it there for 24hrs.
Ideally you want to top balance your pack to 3.65v. Active balancers are not ideal

Good. If I were you I would only use the Neey balancer going forward and set it to only start balancing after 3.45V. Balancers that run all the time can actually unbalance a pack. 

In case one cell runs ahead and triggers bms cutoff

It is around R45 per month.

Thanks. It makes sense. 
I was under the impression, just like the 3x 5.5kw batteries(pooled) provide to the entire load(Essentials), also all 20 panels provide maximum output to the entire load(essentials & non essentials) no matter what phase it's on. 
We have 5 sections(Flats), 5 DB Boards. 3phase is a nightmare with all it's complications.
But thanks a million for the explanation. I'll do further checking on how the loads per inverter/phase output from the Solar. 
Thanks again

Only things i can think is 
The panels are divided over 3 inverters ie 3phases 
 
Each inverter can only feed it's panels to said phase
 
ie lets say pv
phase 1 4kw 
Phase 2 3kw 
Phase 3 3kw
 
So if load is 5kw on phase1
And 4.5kw on phase 2 
 
It would have to assist from grid on those phases
 
The 3 phases are 3 seperate rails solar from the one rail can't reach the other rails
 
The last phases output goes to waste if no load on that phase
Unless if you set the items to work only from batteries to then refill batteries when load is less 
Or if batteries are pooled and thus if the items are set to only use batteries the last phase can push into batteries and the first two phases can assist from the batteries pulling the power the last phase is pushing into the batteries 

I had the same problem . I cut with using baby angle grinder with diamond cutting disc in situ.   Problem is dust ,  but just deal with it 

Thanks @Leondavibe
Came to the same conclusion, when running the battery and loadshedding, I have a good understanding what we use and what is available as well as the battery BMS gives me sufficient information. I also watched a couple of videos around charge cycles and realised that comms etc is not critical for me esp once I understood the charge discharge mechanics of the LiFe battery (video below helped alot)  
I ended up getting the Shoto 5.12 Kw rack mount battery as my brother uses those in his solar install and has not had any issues over the last couple of years. 
Configured the system to charge at 20A and float at 54v, cut off is 48v and have never got close to using more than 30% of the capacity even on the 4 hour stretches. 
Battery charges back up in about 2-3 hours 
Thanks
 

They may not have been charged to exactly the same level. LiFePO4 cells have a very flat voltage curve, so even if they measured similarly before assembly, they may have had widely different states of charge. You'd be amazed how often this question is asked these days. I have a theory, not sure how plausible, that the increased demand means that the battery makers spend less time making sure the cells are balanced, and essentially expect the balancing to happen later after commissioning. As a result it is very common for Pylontech banks to initially report different SOC levels on each module, and it is common for BYD batteries to raise high voltage alarms in the first two weeks.
Some BMSes have impressive balancing capabilities, eg I once saw an active balancer that could pass 2A between cells. The engineer working on it said to me that he thinks it is overkill: The only time that capacity is going to be used is in the first few days... after that it is essentially a waste of money.

Good Morning. 
Thank you all for your insights.
The house we are buying also has a flatlet that is also running of the 8kw inverter.
I will remove the flat from the 8kw inverter and use the 5kw with the lithium batteries for the flat, swimming pool and and borehole pump. The flat will be used as an air B&B to bring in extra income. 
Other option is to use the 5kw to run the 2 geysers ?? 
The extra panels will still go to the sunsynk because this will help with the offset of the electricity that we use from EKSDOM
I was hoping for a quick and easy way but its seems not.
 

Got this working for someone
If i remember correctly
It was just a question of getting the correct cable made up
ie find the pinout of the growatt  and the pin-out of the pylontech
Edit based on reply you can see i lost the plot , but assume the same applies to shoto so data that follows has been changed to match what i find on shoto
 
If they speak the same language naturally it will work otherwise not
 
i would remove all battery cables (to slaves) until you have a connection between inverter and master battery
and then later do slave setup
set all dip switches off (bottom) if having multiple batteries 000000 is master  no idea how slaves need to be set
just that the dip switches respresent 6 bit dial switch
 
 
When making up cables mark inverter side and battery side naturally
 
there is 2 forms of communication RS485 and CAN
the shoto has 3 ports that deal with coms
4 (on layout img) does CAN 
3 does rs485 the right one is the one used to connect to slave batteries (would connect it to the left side on next slave and use the right one to connect to next slave again ie like cascade image attached at the bottom
if coms to inverter has to be rs485 then use the left one to connect to inverter
 
or 4 CAN if that is what inverter uses
 
use a cut cable and join wires from appropriate pins and test until you have a working cable
 
on rs485
The shoto uses pin 1/2 for data rs485 coms and 8 for ground and it seems the growatt uses 1/2 too (not sure on ground)
so try a straight connection from 1-1 and 2-2
If that doesn't work try crossing 1-2 and 2-1 
 
 
 
and on rs232/CAN it uses pin 3/4/5 
5 for ground and 3/4 data
some have a 6pin rj11 and some use a 8pin rj45 connector seems they all use 3/4/5 (salt, just what the 2 manuals i have say)
And growatt uses 3/4/5 too but it has ground on 5
So connect pin3 on battery side  to pin5 on inverter side for ground
and for data
 4 on battery side to 3 on inverter side
And 5 battery side on 4 inverter side
if no success swop the two data lines around ie connect  4-4 and 5-3
 
 
There is a few different shotos so not sure if all the same pin-outs
 
I would make a cable try all the different Li options if no success then alter the cable run through all the options again , too see if one of them matches the shoto
if through all cable variation and settings with no success  , i would just run it in dumb mode 
 
 

Yes unit will still be functional as a ups after you removed the mppt/pmw scc...Will keep this post updated as I continue to figure this out
I repaired more than 60 units the past 18months https://www.facebook.com/inverterman911 ,...the only units in the past that i could not repair was this Mppt fault that only shows 5w charge from mppt.... I cant seem to get my head around it

@Coulomb , you may be right on both counts , sir !    I have only a reference of sites that draw some 1kw or higher at day time (pool pump is on during sunny hours eg.) , so I cannot yet say that the current  behavior is out of specification , there is very little load to offer . The fluctuating AC was at a time when the inverter was battery less, so lets count that out of the equation for the time being. Also , the so called fluctuating battery voltage that I claimed , was due to PV drop where battery added the extra energy when grid not available , so a small charge was affected when the pv came strong again. 
It was load shedding exactly when I was onsite , sigh, so I couldn't perform additional ac blending test ,but my son-in-law will have logs ready for me in good time .
I have introduced an MKS4 this morning , same behavior !. I did a tentative inspection on joints etc on the roof and couldn't fault anything.
So the MK4 is still operating , I took the MKS3 home . I have a string of 5 panels (210V) that I can easily downgrade to 4 panels to masquerade the remote site at home . Hopefully I will find time over the weekend , else during the week.
So we learn until the day we go on retirement. ..... oh wait ....... I am already retired 🥴
 

Well @Steve87 perhaps you can donate one or two dead SunSynk Inverters to @BritishRacingGreen so that he can open them and get acquainted....

Hopefully he will not strip out the IGBTs and MOSFETs to use in his Axpert repairs. 😂

Great news, happy for you, people like you getting value from threads like this, makes it worthwhile to carry on with this journey. 

Chapter 5 : Beginning of the End 
I am definitely not out of the woods yet , not sure yet if the fan controls and relay switching logic , control board and display will work , but I decided last night to introduce the control board and display. I have no way of verifying the operation of the control board , other than to make sure that there i no bad resistance between rail supply inputs etc.
So I inserted the control board and realized early that one can actually misalign when docking it to the main board , which I reckon could cause havoc , and undo all our hard work. I wired up the bare minimum , including the display .
Switch on , and after the usual startup timer timed out , it gave me Warning 01 , fortunately that is fan locked , so i plugged in the 3 fans . The machine then started up  without any further warning or error . obviously the battery icon flashing as well because I have not connected battery or grid to the power chain.
I was satisfied with the progress and decided to  add battery power  in the early morning , which will be an indicator whether all my hard work was worth the while.
No PV  modules added as that is the very last thing i will do in the final analysis . PV1 metrics does show up on the display though , but that is hogwash. I have seen it before on other machines as well when pv mppt module removed .
Today I decided to take the big step to add current limited DC power  to the battery port and bring up the power chain. A bit nervous though .I have two 30V variable supplies I cascaded to set to aggregate of 51V.
Here is me pre-charging the MAX battery input with suitable resistor.
 

and here is me going firing  51V DC , attacking the MAX full-on , no more 'Mr Nice Guy' :

 
The MAX submitted  immediately , produced about 380V on the BUS , opened its front porch with a beautiful sine wave 228VAC .  I also checked the IGBT gate drives and saw the magic in action . One half bridge had a continuously changing PWM to produce sine , wheras the other part of the half-bridge was constant at 50% duty cycle @50HZ.

Have I won the war ? not yet , but many battles yes , still has lots of work lying ahead . So the journey continues ....
 

how did you connect the batteries 
this inverter can only use 2 in line ie 24v
if you connect 3 inline you would get 36v but that isn't suitable for this inverter
 
if you want to add more batteries you must parralel strings of 2's
ie  you can have  2/4/6
and must always have 24v ie 2 in line

My setup is 2 Axpert/Synerji MKS 5K in parallel, 19kWh battery, total 4kW PV. My settigs: Back to grid bypass 48V, back to battery mode 50V.
It's 10h in the morning, sun shining. SOC is around 38%. Due to heavy load (geyser and cooking) the system switched to grid bypass mode. This mode charges the battery from grid with C0.1 and from PV as well, while the loads are connected to the grid. Together they charged with up to C0.19. The battery voltage raised up to 50.4V. It should have switched back to battery mode at 50V but it didn't. I made a try by switching the geyser off. Immediately the system switched back to battery mode. Apparently the Axperts take in account the actual load before switching back to battery mode - intelligent.

From what i have seen 
The shoto balances only while charging and anything under 1a doesn't register as charging ie if under 1amp the battery goes into standby 
 
The cell balancing only happens when cell voltage goes over 3.5v
 
Naturally the balancing does not happen for long as you can imagine cause that is steep part of the curve
 
My pack operates in dumb mode ie no coms with inverter
 Does charge on a Li charge algo ie CC CV and zero float applied
 
I do use the coms via laptop to see the behaviour
 
No balancing happens when it is at 100% soc and not charging
The battery just goes into standby mode
That Is the behaviour on my model anyway

Some BMS use a estimate rather than a shunt with a coulomb counter. Some BMSs are simply poorly calibrated and there is no way to fix it under-reading current.
Having an accurate coulomb counter in the BMS makes a world of difference since a LiFePO4 battery can not be measured with voltage without having a 40-50% error as the direction of the current makes a huge difference to the voltage. (Unless you do not place any loads on the battery while charging)
My Daly actually works pretty well (200A Smart BMS). I also use home assistant to step down the charge current as the cells approach 100%. The balance function is a bit of a joke, I probably need to invest in a balancer at some point. In the past I was annoyed with the daly as it seems to reset itself to 100% but that turned out to be a poor contact on one of the busbars, once torqued properly the problem went away (discovered when I started logging cell voltages on a graph) I also discovered that the SOC was out by roughly 20% after 2 weeks where the weather did not permit a full charge, which means that shunt software samples too slow and drifts over time.
Getting a good ROI out of the cells require a good bms, otherwise you will be guessing and using too little or too much of the battery