87 Dream

Thank you Coulomb, I'm learning every day. That diode protection certainly works well if there is only one such string. I'm questioning myself, if there are two or more strings in parallel, the string with a faulty panel will have less output voltage than the other(s). That would result in significantly less output power - wouldn't it? And as less sun power is converted to electricity the panels would heat up faster than the others thus reduce output voltage even more.

If a panel went completely open circuit, yes. But there are diodes to prevent the voltage across the panel going negative (usually 3 diodes, across each third), so that generally one panel going out won't cut the whole string. The exception is where light or the total number of panels is marginal, such that all panels are required to produce any output at all.

Hi to everybody,
I thought it is a good start my first post with showing what I have made.
the existing grid is 3 phases on a large area with 3 small lodges for vacancies rental. (+ workshop + office)
the target was to reduce grid counsumption and being able to feed the internal grid between the 3 lodges in case of black out (quite often in summer)
the main issue was that each lodge has its own elec board, the distance between lodges is large and distance to PV is large also.
because of black out, the idea is to have battery storage. so if battery storage, the next idea is to use it, so zero feed into grid.
So I end up with 100% injection solution in the local private network with zero grid injection and a supply switch to be able to feed the private network in case of black out.
it took me some time to setup the energy meter, the modbus card and the 3P inverter to work correctly in this mode but it is so satisfying to see the energy meter regulating import power to ZERO !!!!  If some are interested for same configuration, I can help.
the PV field is made of 28 panels 290W each arranged in two fields of 14 series(Est and West field for more efficiency with sunrise and sunset shadows)
other intereting point is the use of second hand small electric car batteries that I reworked to accordate as a 48V 300Ah Lifepo4 battery.
here are some pictures
 

install finally started today.

Yes, the video was made in 2017 and 100% correct at the time. I had 2x5kW Axpert inverters in parallel. I hammered those inverters and never had a problem with them. The biggest disadvantage of those inverters at that time was that when running on solar power, the mixing of power came from the batteries. My batteries were very confused, they never knew if they were charging or discharging. The battery power chart looked like a lie detector test spiking up and down the whole day. I am not sure it did the batteries any good. After about 2 years use, there was a marked reduction in my battery capacity. 
In the latest models, power mixing makes use of grid power, if available, and not the batteries. That to me is a huge improvement. Now the batteries are only used as backup power once no grid power is available. The one disadvantage still exists that power only moves in one direction. Your load on the the dedicated circuit for the inverter might be low and you have load on your grid circuit, but you cannot feed them. 
Sizing of solar panels array becomes a problem, especially if you are not sure of how much power you consume on average during the day. Oversizing of solar panels becomes a waste, as half the panels do nothing as the inverter will cut down to what is required according to your load. No matter how many solar panels you install, they will never be the right amount. At times you will have too many and at times you will have too little. 

Hahaha its the Hubble. As tempted as i am there's no use in opening the box at this stage. And its farkin heavy

A solution to this problem might be to put a notice label on each battery, CAUTION “Keep sharp objects, dart boards and nail guns at least 3meters away from battery to avoid runaway temperature”😂
 

Well at least for my first post here I got to page 3! 🤣

Thank you for all the input.  Revov sent their tech out to me and he changed the RS485 cable also set the one to master and other to slave.  Also connected his PC to the one batt to adjust the charging Amp from 40 to 101AH  he reckons it will stabalize in about 2 weeks.  We wait and see now to see if rate of charge and discharge is more equal between the two now.  One batt was in state of DSG (discharge) and other was IDLE.  
Thank you again for all the input.
Now I must master the system settings to get most out of the batteries and the PV. 
Google is my friend but I think I ill stay right here on POWER FORUM - You guys rock!😬

I was trying something similar. Finaly found someone posted Inverter-Battery conversation on the arduino forum:
https://forum.arduino.cc/t/rs485-modbus-between-solar-charger-inverter-and-battery-setup/602331/11
If I do not reply on the 0x61 message, my inverter EaSun iSolar SMV III / Axper VM III asks three times after boot and does not ask again and shows no errors.
Implemented a small Python prototype as proof of concept.
The goal is to integrate it some day into diyBMS.
pylon_RS485_working.zip

Good point , isetech .  Which begs a new question, what is the magnitude and quality of the incoming supply when the the grid starts feeding again from Eskom?  Maybe the gas arresting part of a surge protector strikes because of this.
Only way to find out is next load shedding session switch  the Main breaker off , and only re- connect manually after the end of loadshedding. If ok, it's a giveaway that the transient state of Eskom supply when they re-connect is ungracefull/unstable.
 

I wish they wouldn't call it a King Max when it's not zero transfer. That to me is the hallmark of a King.
Not your fault, just having a grizzle. It's hard enough playing "identify that model" as it is. 

Haha you guys are going to give me buyers remorse! 😂

Absolutely.
Yes, the financial layout was a hard pill to swallow in the first few weeks back in July, but with this latest round of loadshedding, it has been the best investment we made to the house. And not to mention the ability to continue "living" when the grid goes down.
All I can say to those who are thinking about doing this or are hesitant to make the investment, try and make a plan to go for it. You certainly won't regret the feeling of "freedom" you get when you watch solar powering your house during the day and batteries powering your house at night.

Its horses for courses I suppose in this debate.
I started out with the SolarMan app but found that to be too clunky and limited with data availability. Was looking for something more real-time to manage my system.
Did a search on this forum and the first one that came up was Solar Assistant. Did the research and found it to be what I needed. Ordered online and the kit was delivered within a day as advertised. Took me all of 15min to install the Pi and get it running and have never looked back.
I was upgraded to the beta version which included the Power Management tab being activated for my Deye inverter and that allowed me more control over the System Work Mode feature remotely especially when loadshedding struck again.
Support has been good too.
I have subsequently looked at the ICC software but am very happy to be with Solar Assistant.
MdF

Just guessing on figures here but cooking can take 1-2kW of energy per hob while a gas geyser can maybe be 14kW of energy or more.  A 48kg for a gas geyser can easily be used up in 2 months.

Hello and thanks for so many interesting and important informations I find on your site
I  just started building my installation. This Voltronic inverter will be my choise, togheter with 18 old 175W PV's, and soon I hope 16 cells from AMY WAN. then a DACIA SPRING the new all electric car, only 12.500€ now here in France. Good enough for us, and bye bye mister diesel.
5.6kW for us is perfect, 5kW was a bit just for us all the way. Voltronic, yes for first start, money is important for us, but it will give me enough experience to go better perhaps later, I hope it will last a few years, nobody talks about general lifespan. (Sofar is I think my dream for what I learnt, low self use, no fans, 10 years garanty, anyway, to expensive for now)
My question that I cant't find is: What is the difference between the MKS and the VM serries, there must be more exept the 500VOC of the mppt
I hope you can help with a answer or a explaining link.
Very much thanks, I just hope you have a nice evening
FransFrance

Ugh sorry yes, late night post.  I meant to say parallel.  I'm charging them at 3.6v @ 5amps.
I'm still waiting on my BMS so I don't actually mind too much if it takes a long time to bring them all up to the same level of charge.

I thought I would add this to the forum as people are being mislead and no one is doing anything about it.
I'm an electronic engineer and have 30+ years experience in electronic design of many types. Specializing in microcontrollers mixed with analogue designs and the like. From concept to final product. 
A couple of years ago I did a solar camera installation for a farmer in Limpopo. Long story short; I used Royal 45Ah and 65Ah lead acids as the battery of choice. Then after 2 years they started failing. They couldn't hold current anymore. The solar is only 140w 7.7A 18v panels. My charger is a self designed circuit based on the LT3790. Capable of delivering all 7.7A of current at 14.7v. I then went to sintech in 2020 (will NEVER use them again) and bought 9 new batteries; they analyzed my design and recommended Omnipower 60Ah 12v Agm/VLR batteries. So I bought them. 6months later they started to fail. Could not even deliver 20Ah (or 1.5A for 14Hrs) I took some back and they accused me of exposing the batteries to high temperatures of 45degrees... WHAT! I took the OPR60 data sheet and showed them that at a constant temp of 60degees C they say the battery must last 2years.. at 25 degrees at leat 10 years!! They therefore did not want to honor the warrentee.. 
I also bought x2 100Ahr batteries and installed that in my garage on a 1500KVA UPS. At a constant temp of around 25degrees in a 19inch rack. They too are now starting to fail. 1 year down the line; Being charged by the UPS and doubled with solar. 
There is a fundimental issue with omnipower batteries. And I think I know what the issue is. Nothing to do with Temperature but all to do with charge current!!
But Sinetech refused to honor the warranty; even when they advised me on the batteries and now DENY EVERYTHING flat out. They never knew my application.. really..
I'm in the process of making a consumer goods council case against them. I bought temperature loggers and logging battery temperatures. I also cut some batteries open to see if the batteries are dried out as this is the tell tale of high heat.. 
I'm also buying a battery analyzer to test the batteries
I believe there is a fundamental flaw in these batteries and if NOT charged in lab conditions will deteriorate Very quickly!! 
So be warned. Omnipower batteries are NOT worth it. Communica also buys them from sintech and I bough one from communica which also started to fail.
I will post my results of the tests as I go along. Even trying some desulfication techniques on the dead batteries NOW 1year old 
 

Hi all
Thought I start a topic to go through my journey of creating my own Lithium Iron Phosphate battery pack.
Overall my objective is to create a battery pack that is equivalent and/or exceeds the quality of pre-built battery packs at a lower price point.  All prices include shipping cost
Parts list:
JBD BMS @ R2700 total (once off expense, including shipping) I've used JBD BMS before.  They are without a doubt the best quality you can go while still paying very little.  Plenty of info around about them, compared to Daly BMS for example, would not recommend Daly. 18x Cells @ R750 each @ R13 787 total (including shipping) I see the company already put the price of the cells up.  It might be a good idea to try find another supplier.  These are 2nd life cells.  Meaning they were first automotive grade (highest grade) used in cars and after losing roughly 15-20% of its capacity is no longer suitable for a car but is still suitable for storage.  The advertised capacity already includes the loss of capacity.  In other words, they've tested the cells and re-sell the good ones 250A Class T-Fuse @ $35 (ouch) + Fuse holder - $24 (need something more cost effective here) I already had this fuse.  These fuses are much bigger than the picture makes it seem.  It is about the size of the palm of your hand.  The have very high rupture capacity, 200kA at 120vDC. Meaning it can break 200 000 amps at 120v safely.  It is important to note that battery packs can put out enormous amounts of amps in a very short duration.  If the short-circuit breaking capacity of your fuse is too low the fuse and holder will literally explode into pieces (best case).  I think this fuse is probably overkill so another fuse may be suitable at a lower cost.  I already had it however.  Open to suggestions for another type of fuse DC Disconnector @ $30 (no suitable for voltage and not cost effective) Do not recommend this disconnector.  It is only rated up to 48V and I can audibly hear it make spark noises as I turn it.  It isn't up the task of these high voltage packs.  Still this is what I have at present.  To compensate, I'm adding an anti-spark push button.  A button you press that will connect the battery across a resistor to prevent a spark but allow the inverter to charge up.  The way I implemented mine is, you press the button and it stays active for a minute so you can turn the disconnector.  But overall I really dislike this configuration, so open to ideas for better disconnectors. Aluminium flat bar 30mm * 2mm * 2500mm x2 @ R280 total (once off expense) To connect the cells with each other I need a busbar.  Initially I was planning on using copper but, the equivalent busbar 30x2x2500 would cost roughly R1500.  Aluminium has roughly 60% the conductivity of copper.  I'm aiming at 70mm² copper equivalent which means double stacking a Aluminium flat bar. M6/6mm threaded rod & bolts ( R25 + R40 + R25 = R90 ) This depends on your cells but mine takes M6.  I bought a single length of threaded rod with some washers.  Additional I got some M6 flange nuts from a local nut and bolts supplier.  I cut the rod into suitable lengths using a hacksaw. Considerations
One of the considerations is what you want your battery's voltage range to be.  This is determined by how many cells you put in series. 
The number of cells is series is denoted by cell count and s.  In other words, 16s = 16 cells series, 17s = 17 cells series, etc.  There is an additional moniker that is more prevalent in the eBike circles, p.  so 16s2p = 16 cells series with 2 parallel per cell.
LifePO₄ has most of its capacity between 3v-3.5v.  That is the voltage range you want to be operating it.  The "nominal" voltage is 3.2.  Although you can "theoretically" discharge your cells to 2.5v, the last 0.5v is the last 10% of the battery and the zone in which you wear down the cell rapidly.  So just don't do it.
Configurations for 48v inverters
16s = 48v -> 56v 17s = 51v -> 59.5v 18s = 54v -> 63v Notice that 16s is the closest to your typical lead acid 48v battery bank.  However increasing the number of cells increase the watt hour capacity you have and it also decreases the current through your battery bank.
My Axpert inverter can handle, at most, 18s which is what I went for.  I did it for a bit of extra capacity and lower current which theoretically increases efficiency.
Process
First off I sketched how I imaged I would arrange the cells

You can pretty much arrange this in any configuration, you just need time to play some lego.
I ordered my cells:

Having received my cells I was able to accurately determine the size I need in terms of busbar as well as screw size.  My cells were 6mm screws (M6)
In terms of busbar I decided to go with 30mm x 2mm x 74mm.  I calculated that I would want to double stack my bus bar to give me 30mm x 4mm, so in other words 120mm² (equivalent wire thickness).  But with 18s I needed to buy 2x flat bar and thus decided I'll have extra so may as well go for triple stack 30mm x 2mm x 74mm.  That would be equivalent to 180mm² wire.  At approximately 60% of the electrical conductivity of copper, that is equivalent to 108mm² copper wire.  Definitely enough for virtually no voltage drop.
At first I thought I would solder together the two pieces of flat bar on top of each other.  But even using a blow torch the solder would not adhere (tried different fluxes I have, no success).  So essentially I'll just bolt them down

Yes these aren't perfect.  I cut the holes with a hand powered drill and 6.5mm bit.  And the flat bar was cut with a hack saw.

To clean up the flat bar after I drilled it, I used a deburring tool I have and then cleaned up the plate with steel wool.  I've used the steel wool before to clean up copper pipes and it leaves a really nice finish.  As you can see here, if you overlook how the holes don't look completely center and the deburring was done hastily but the finish looks sort of decent.  Making these bus bars up to what you see here took roughly 6 hours, its slow work.
Equalize the cells
Before connecting the cells in series, the general advise is to connect all the cells in parallel and then charge them up to 3.65v and keep them there until the current being consumed is very low.
    
I already have a bench power supply that I'm using for this purpose  But progress is pretty slow.  I suspect the batteries were provided to me near empty, I'll probably some more days to go before these cells are anywhere near fully charged.
The BMS I'm using:

And the positive side disconnector I created with a precharge toggle switch to avoid that spark when you turn it on: (the switch is momentary, so it has to be held in position)

Fully assembled battery:

BMS app:
  
The BMS without load versus recharging after I put some load on it
 

100 Amps at 48v is 4800watts.  You should assume total losses in the inverter to be equal ~85% usable power so call it 4000 watt usable power.
Your battery needs to be sized to your systems maximum demand, at the very least. If you size it smaller than the system, it is the sign of an amateur.  I say this because what is preventing the system from being used up to 5kW?
Considering I paid R2700 for a 300amp BMS (with delivery), it just seems silly to try save R500 on the overall cost of the system for something like that.

I bought 2nd life cells.  Which is costing me R13k for 18s.  Whereas a 16s 100Ah would cost R20k+ (and almost certainly use a much worse BMS than I'm running).
So I think the cost difference is significant.  The question is how it will perform long term, but at ~R8k saving, I'm willing to give it a go

Just as a matter of interest , the reason for the subtracting function , is to reject common mode noise. Twisted pair cable are shoosen for this purpose, so that equal amounts of common mode noise are typically injected on both lines. Now because the receiver amplifier subtract the signals , the equal noise amount are subtracted , resulting in zero noise.
It is because of this common mode rejection that we can easily transmit RS485 signals on a 2 km transmission line , even further if you willing to drop the signaling data rate.

Thank you @87 Dream - thank you for the feedback, changeover switch it is...

Can you please share the link for the Mecer.
If, you are not planning for solar, an online inverter would make more sense but the cost and need of pure sine wave should be justified first. A lithium battery would still be better in any case.