Very correct!!! Full length bus bars will certainly reduce the number of current loops and overall contact resistance. I have modelled the bus-bar model circuit with LTSpice and it works.
I like the fact that DIYers are opening their eyes to the benefit of AC-coupled systems; I was crucified here on this forum by ignorant people on the possibility of using grid-tied inverters/micro-inverters for off-grid systems.
Secondly, the benefit of utilizing high voltage dc inverters for large systems cannot be over emphasized. The overall system dc current is much lower, I2R losses are greatly minimized, and optimal charge rates for the batteries are achieved.
Please don't moan about high voltage dc and all the unverified bla bla cliches that make me sick. High voltage AC sources are still much more dangerous to the human body than similar DC voltage sources. See this link for the skeptics: https://www.youtube.com/watch?v=snk3C4m44SY
so i will try as much as possible to take your request line by line.
For a start am not too sure that there is a 30KW 3 phase par say, NB: 1KVA = 0.8KW but if judging by the 40KVA in your third paragraph, then that's a 32KW system, again not sure of its existence but eh! I.D.K.I.A So I guess the installer has an indian inverter type in mind. ¬ For the panels Not bad the solar panels are good but i would do things differently.
60 units of 200Ah - to me is a bit much, if right he'd like to do a parallel string of 360V x 200Ah x 2 = 144,000Wh [ i'd say from your findings you've things right, vaguely. but charge controllers determine solar panels used and loads and charge time affect it all.
On the battery too, i'd say spot on.
since Lithium battery is newer to this hemisphere, I’d proceed with caution to play safe.
BUT
I would have done things differently to achieved a more simple and efficient system.
I will choose a 48V system, eh! I don’t want to die of high voltage while connecting my batteries due to a cut in my safety gloves.
Now that am certain of my system voltage, i will proceed to get premium product to cover my huge investment.
For the Inverter Since this is a 3 Phase installation I will go with a Victron Quattro inverters/charger of 10Kva, paired to work in synergy of three phase [R,Y,B] this way I’av bypassed high voltage and still end up with an equivalent power, even better with 1.0 pF [power factor].
Overview I will make use of an AC - DC coupled system, so that my loads will run off my PV - inverter during when the sun is up and my DC charge controllers will charge the batteries and still be able to provide more in case of more power needs and the wake up the installation in case of battery too low to get inverter systems up when low.
So i will go with a PV Inverter of around 25KW which should be sufficient to power load when needed and especially at full power and a solar charge controller of high Voc that can charge my battery when PV inverter covers my loads.
i.e. 92 nos of 300W canadian solar panel to a 25KW PV - inverter [ allows oversizing] and 18 nos of 300W canadian solar panel to a smart charge controller
in total 110 nos of 300W panel equivalent to 33KWp.
For Batteries Concerning the batterries I will go for Hoppecke batteries, of 2V ~1500Ah nominal @ 72KWh or 2900Ah Max. @ 139.2KWh
this means that I won’t change my batteries in the next two - three years soon but more of five to seven years, and making sure that ROI [ return on investment] is guaranteed.
With a easy to understand system.
Credit: Rendezvous Solar free free to contact me if non of the info is not clear enough . Rendezvoussolar@gmail.com
hello spyglass, those of us using inverters do so not necessarily because we 'love' inverters but because of the convenience it provides.going the dc route may sound cool, I.e no extra cost of inverter purchase, no power losses arising from stepping up to a higher voltage, etc but when it comes to getting actual dc equipment to work with your system, that is where the nightmare begins.besides that, the size of wires you need for a dc only household would be like triple the size of wires needed for ac.then you have to deal with availability of dc spares and the rest. for ac however, once you get your inverter, every other thing falls into place.
Hello all, every reasonable online forum usually have strong admins. Anyone that breaks the rules of forum engagement must be banned for the sake of sanity. Where are the admins here
This assumption is wrong in theory and in practise. Electricity flows from high potential to low potential.
Scenario 1 If say your PV is producing 1000w and your load is using 1200w, 1000w goes from your CC to your load, and the reminder 200w is taken from the battery.
Scenario 2 If your battery is full and your PV can potentially produce 1000w and your load is 1000w, the load from the PV goes straight to the inverter (Your battery is completely ignored.)
Scenario 3 If your PV can potentially produce 1000w and your load is using 500w then 500w goes from PV to load and unused 500wh would become potentials.
Scenario 4 if your battery is low and your PV is producing 800w but your load is using 800w,all 800w produced by the PV goes to the load. Non is left for the battery.
Remember like I said, electricity moves from high potential to low potential.. The lowest potential in all the above scenario is the load, not the battery. The battery always has a higher potential than the load, The battery charger in this case the PV/CC has the highest potential (so long as we are using a proper charger with the right voltage)
Its just against physics for a battery to draw electricity more than the load. The above is the theory.
For the practical, I have a Victron Battery Monitor BMV 700 the BMV comes with a current shunt which is connected to negative of the battery, inverter DC input negative cable and Controller dc output negative cable. The positive cable of the BVM connects to the battery.
The BMV monitors currents going into and out of the battery from the Inverter and CC. The BMV display shows gross net input and output to the battery hence 1 if my charge controller shows it is producing 24A and my load is 10A, the victron battery monitor shows 14A going into the battery. and this is confirmed by the battery voltage.
If I turn off the 10A load, I see the BMV showing 24A going into the battery. If I turn off the CC, the BMV will show -10A being drawn from the battery.
If my load is say 24A and CC is pulling 20A, the BMV shows -4A leaving the battery.
This idea that all power from the cc first goes to the battery and the load pulls it from the battery is false and against the principle of how electricity works. when I have time over the weekend I will demonstrate the truth of this.
This is the most practical and theoretically correct answer to the argument.! If you are into solar DIY and you don't have a basic electrical or electronics background ( either thru formal or informal learning), you will most definitely fail. There are tons of "electricity-for-dummys" books and materials online if you need help.
Exactly that is intended operation. The grid is not available( intentional islanding mode) to sink the variation in power and you do not want battery voltage to spike with a large load is switched off or something trips
For reasons debated earlier on the forum in Nigeria, theoretically, you cannot run grid tied AC inverters till all regulations are in place. See this interesting video - For the layman this video explains it better ( start at 40 Sec to get past marketing stuff) - https://www.youtube.com/watch?v=Bq1ShAgw5no?t=40s
Although I have 5 contractors in series - One input Quattro, 2 output quattro, 3 - Power contactor for grid-tied, 4 , Ziehl islanding relay, 5 ( Auto changer of gen and NEPA( German standards require 1 and UK 2) to avoid all possiblities of malfunction
E.g. for Nigeria what should be the ROcof ( df/dt) nobody knows. There is no standard and no practical knowledge.
I am eagerly waiting when the net metering takes off and I can actually put a large PV inverter coupled with my Victron. Till that time we are at the mercy of clever gimmicks to get around the technical problem the politicians should solve.
BTW. the Ziehl islanding relay setting options are attached - if you look at the settings you will realize the importance of having values from regulators
Hi Makoavele, don't be misled by the 240Vac in the specs: it is the voltage between the split phases North American 2 hot legs, L1 and L2. L1 or L2 to Neutral is 120Vac, 60Hz, while L1 to L2 is 180deg out of phase to give u 240Vac peak to peak. Don't confuse it with European single phase L-N of 230Vac, 50 Hz.
Sorry, I missed the CC - the CC is through Canbus to CCGX/Venus GX and then by .Ve direct cable to CC. the CC stops charging in few seconds if it loses communication - It's a standard implementation for Victron Nothing special there
Thanks Pranil for your explicit explanation. Basically you charge to approx. 100% and all forms of charging will cease. You will then be running off your battery pack until a pre-determined SOC before the charger engages again.
There is no floating arrangement on your CC, hence your PV cannot supply load power when battery is fully charged.
Which micro-inverter are u utilizing? I only know of the magnum MicroGT 500 that can throttle its power with frequency shift control. The rest of the micro-inverters in the market will NOT gradually reduce their output power with frequency shifting, rather they get knocked offline completely when a pre-determined frequency is reached. Unfortunately the magnum MicroGt 500 is yet to made available for european 230Vac 50Hz systems.
My decision was based on mainly two factors ( reliability of both battery and BMS) and availability in Nigeria for off-grid use as Lithium are temp sensitive. I started the process way back in May before coming to the final conclusion that building your own battery was fraught with many issues such as canbus integration and component failure risk as well as the jungle of wires and constant babysitting required which is pyscially not possible by me.
Pls. see attached excel where I have contacted each supplier for both commercial offers and technical details to ensure proper integration. Suppliers who refused to support Victron and axpert ( zinox/voltronic) inverter were dropped out . The BYD won the race mainly because - Availability off the shelf ( I wanted to finish before December beginning), Low per cycle cost ( comes lower than Trojan). It also helped that BYD is the largest manufacturer of LIthium batteries and Electric cars ( including JV with Mercedes EV's) https://en.wikipedia.org/wiki/BYD_Company and best of all one of the few batteries apart from PYLON which can be added in stacks of 2.5 KWH as your system grows without affecting warranties. BTW The warranties on Lithium are 10 years as general practice
I also have an order a relatively new company called herewin which will come in January. They cannot support canbus but the price was only 3000 USD so I decided to take the risk and will try to use it with PRAG 5 KW ( yet to get hold of PRAG BTW ) to clarify the absorb times
On the issue of the BYD the biggest advantage is that BMS of every 2.5 KWH unit ( called B- PLus 2.5 ) is integrated. But the BMS does not talk to inverter but their own box .( BMU- battery management unit) This BMU can be upgraded anytime for the firmware to support more inverters or models without changing anything in the battery which is a big plus point the battery and BMU connect over RJ 485 and located away from each other if required . The BMU is also cheap 69 USD compared to other brands like sonneh which cross 2000 USD
The charging the B- BOX is through Victron inverter at 70 Amps ( inverter limit ) as well as my 2.5 KWp solar 48 V , 45 amp CC and 500 watt Grid-tied ( together max 136 amps) which is the exact limit of the charging normal 0.7 C max between 12 to 50 DEG C
The BMU informs the charger /inverter when to switch off charger through CANBUS including the current limit for charge and discharge based on battery temp. It is actually fun to see the battery charging as it reaches 99 % at full 70 amps in then in next one minute the current drops to Zero As a added safety precaution additional Allowed to charge and Allowed to discharge contacts Hardwired to inverter which are NC so in case BMU fails the inverter stops charging( allowed to charge off) and also switches off ( allowed to discharge) The battery has also it's own safety contactors built in per 2.5 KWh with LOw/Over voltage and current limit .
Th technical details are too many to elaborate as the forum format is not very user-friendly ( limits attachment per post) those who are interested can contact me for more details directly on interested models and use case scenarios/recommendations.
Nice setup. How do you regulate the charging of the lifepo4 unit from the solar CC and 500w grid-tie side of things? Same CANBUS?
pranil: How do I contact Prag technical fellows? Anybody can give me an email or phone. I have a 5 KW Prag which mentions Settings for LIfepo4 in manual . I would like more details on it as I plan to install LIfepo4 but worried about absorption times. The full charge and discharge voltages match with my batteries exactly .
Hello Pranil, which lifepo4 battery system did u finally purchase and have u commissioned it yet?
pranil: In the interest of sharing pls. find attached my comparison of LIon batteries ( which can be leaglly imported into Nigeria) and lead acid
The transport costs are approximated to the higher side. All battery prices are from manufacturers with direct quotes
Conclusion - Unless NERC increases unit rates of makes net metering legal. LEAD ACID comes out winner
The only exception is Smplifi USA who claim to have more than 10,000 Cycles life at rated capacity
Very thorough research work! An additional column stating the recommended and max. charge current will also be beneficial. Some customer applications may require battery banks with fast charge capabilities or high current charge rates. For example, the Simpliphi 2.6kWh, only has a max charge rate of 25A or 50A if paralleled to 5.2kWh (48V version). Whereas BattleBorn and BlueNova batteries can accept up to 1C charge rates, effectively making them a better choice for fast charge or high current applications.
bigrovar: Kai, Sun is literally not smiling in my neck of wood. I had to roar the Gen back to live last night no thanks to 3 days of diabolically dark clouds. I had to cut down on powerful loads like fridge and freezer hence my turning on the gen before all frozen food go to waste. I think it is time we really look to diversify our source of renewable energy and start to look into Wind Turbine as an addition complementary to solar. especially for times like these and also to help with night load. For am just looking for a 600w wind turbine setup. Even if I can get 200w from it from an average day wind is a win for me because that should be more than enough to power the freezer and cover the night load (at all at all na him bad)
anyone here has any experience with wind turbine generators?
Hi Bigrovar, Will increasing your PV production capacity help your situation? Like doubling or tripling ur current PV capacity?
These LiFePO4 need to be run with a BMS (Battery management system) . If you haven't worked with lithium cells then it would be better to use Lead Acid Deep Cycle Batteries which are more forgiving to accidental mistakes.
-------------- Me, I don't know anything about BMS. But do I know anything about inverter before? what we need is un interrupted power. so, am sure if need be , one can overcome it, is this something to worry about?
Normally, as long as I put my battery in a ventilated area. and make sure it works fine. Is there any other factor to work on? OR do I need to engage the services of a local professional? in installation and on going usage.
The seller has not quoted the Max charge and discharge current. The cells pre 2015 were all low rated ( mostly 50 Amps) ( 2.5 KW on 48 V max)
Please check that. Also cycle life was low ( 1500-1600). Nowadays cells with 5000 cycles are available.
Herwin ( china ) gave me a quotation of 1900 USD exworks of brand new for 10 KWH (48 V) including BMS and assemled system - I have also posted the freedomwon pricing earlier
The used ones are coming to almost 2000 Pounds for 48 V plus you have to use cables, MCB, fuses etc.
If you are looking for 24 V Soladin in Ghana is selling Lithium Ion assemblies with high current rating
what you have asked is beyond me. Unless I hire a local to go do a local testing there, and not sure how to even find one.
Quick one: would it be worth it if I have to hire someone to go there and do a test. and what will I be looking for from the specialist actually. if actually it's: 90%. will it really be worth it?
second. what will you recommend overall considering my situation..am I over reacting with these phosphate versions or its the real deal like the guy proclaimed.
To do the test, you basically hook up each cell to precision dc power supply through a coulomb or energy meter like the trimetric or victron energy meters. But before then, you will have to drain each cell to zero SOC state, which is at 2.5v resting voltage after 24hrs. Set the bench supply to constant current mode @ 0.5C rate. Set an over-voltage cutoff at 3.65V and allow it to charge up until the voltage reaches 3.65v and cuts off. The energy meter should be able to read off how much AH put into the cell. As a confirmation, modify the setup and discharge the cell through the energy meter to a load resistor to 2.5v after resetting the energy meter.
what you have asked is beyond me. Unless I hire a local to go do a local testing there, and not sure how to even find one.
Quick one: would it be worth it if I have to hire someone to go there and do a test. and what will I be looking for. if actually it's: 90%. will it really be worth it?
second. what will you recommend considering my situation..
LifePO4 is the future of energy storage if the price continues to fall. It's advantages far outweigh the aging lead-acid technology. But you need to know what you are doing with them. The seller's claims are generally true for LifePO4.
And no way for me to test as I do not have the resources to.
You will have to invest in some specialised dc bench power supplies and coulomb counters to properly test, balance and characterise these cells b4 use. Some people may advocate the use of a battery management system (BMS), but very experienced users bottom-balance only and it's been working for them.
damola1: Good people. Great Nation. Good morning to all o. Please. abeg una, help me made decision:
Is this a recommended good buy?
I use a Magnum RD4024E inverter/charger in my office. and I have an offer for the following for: 80k each. 16units. We normally regularly have up to 12-14hours electricity daily. But I have also been advised to make sure the batteries don't get dead as that could make them die faster. so, after this purchase, I will probably be working on a solar panel backup. I run a 247 service. and primarily use the batteries for fans , computers, and nothing more. all acs are never on the inverter.
I am particularly interested in these because they are Lifepo4. and the seller confirmed the are still up to 90% good.
Very few cycles used, has more than 90% life left!
210 Ah Lithium Iron Phosphate Battery
4 Cells = 12v Lead acid Battery 8 Cells = 24v (2 X 12v) Lead acid Battery 16 Cells = 48v (4 X 12v) Lead acid Battery
Capacity: 210Ah Height: 147 mm Width: 429 mm Length: 147 mm Bolt Size: M8 Voltage nominal: 3.2V Charge voltage cut-off: 3.6V Discharging cut-off: 2.5V Chemistry: LiFePO4
LifePO4 cells are delicate and unless you know what you are doing, they can easily become expensive bricks very quickly. You have to do a very comprehensive capacity test to be sure you are not being sold bricks. Don't take the seller by face value. Can you share with us who your seller is? I am also interested in getting these cells too.
A grid is a legal term referring multiple energy sources connected together for distribution to multiple legal entities so when you call an inverter grid tie it means It is coupled to other energy sources which are regulated based on national laws Infact based on your recommendation the first search of grid tie inverter brought me to wikipedia
Quote " A grid-tie inverter converts direct current (DC) into an alternating current (AC) suitable for injecting into an electrical power grid, normally 120V RMS at 60Hz or 240V RMS at 50 Hz. Grid-tie inverters are used between local electrical power generators: solar panel, wind turbine, hydro-electric, and the grid.[1]" In order to inject electrical power efficiently and safely into the grid, grid-tie inverters must accurately match the voltage and phase of the grid sine wave AC waveform. Some electricity companies will pay for electrical power that is injected into the grid. Unquote
The emphasis is here again GRID-TIE - . A simple google search will also take you to various manufacturers use of grid tie inverters recommendation and certifications for grid tie which specifically refers to connecting to local distribution grid
Please note that Grid tie inverters are not only frequency based control but they require a complex mechanism to detect abnormal grid conditions such as power swings and ramp rates which are different for every country . A grid tie inverter can also inject VAr into the system or disturb the static var compensations as well as contribute to harmonics
Just to make point clear about google I am not some D.i.Y enthusiast who has read on internet but a practicing consultant for more than 25 years and in renewables for more than 9 years for a leading German consulting company . I have advised utilities and private companies in many countries both in east and west africa on Power systems , renewables and sustainable energy . I use off grid system for my house as a hobby and out of necessity and constantly experimenting with it . But I am worried when people are not aware of the dangers the systems will try to take only partial knowledge and create problems down the line for the entire solar enthusiasts If interested you can have a look at the publication coauthored by me for ministry of power on Nigerian Electrical system with emphasis on Renewables and rural electrification http://www.energyplatformnigeria.com/images/Library/Energy_Sector_Study_(2nd_Edition)_-_GIZ_NESP_2015.pdf http://www.energyplatformnigeria.com/index.php/overarching
Every responsible inverter manufacturers will tell you that in places of weak grid like Nigeria Grid tie or even AC coupled systems are bad idea . It can lead to instability , flickers and other unanticipated issues .
P.s. I am not stopping people from using the grid tie inverters just let them be aware that there are both technical and legal pitfalls ahead of them specially when Grid tie inverters cost much higher than offgrid /hybrid inverters and have lower overall efficiency in a typical residential house with battery backup .( converting solar DC to Ac and then back to DC to charge the batteries) . Unfortunately due to severe requirements placed on them because of grid tie they turn out to be more reliable and durable then typical offf grid inverters and hence preferred even for off grid
Oga Pranil, after all your previous rantings about the supposed "Ilegality" of using grid-tie inverters in an off-grid system, you are now dreaming of implementing an AC-coupled system using the same grid-tie inverter (in this case microinverters hard-coupled to PV panels)? You are trying to implement a variation of an off-grid, AC-Coupled system with grid-tie inverters called a "GRID-FREE" system, yet you argue that grid-tie inverters must inject into the national grid. Please explain to the forum how you plan to stabilize the national grid and also show us all the NEC / NERC code compliance certificates and permits that must be issued to you by our beloved NEPA ...sorry Eko Disco....
what happens to ur office loads being powered by a gridtie inverter that is not connected to the national grid and it starts raining or there is brief cloud cover? the office shutsdown? Put on generator?(forbiden in this forum ), the micro inverter on each panel, what is their cost vs the added power gain?
Sir,
This type of systems usually have a battery backup option. That will take care of the scenario you described above.
In addition, ac-coupled systems are not only restricted to the use of micro-inverters. PV can be wired in strings to a standalone grid-tie inverter via a combiner box. The standalone grid-tie inverter (sometimes called a String or central inverter) can then be ac-coupled to a battery based parallel inverter hooked-up to a battery bank. However, PV shading and orientation poses significant issues with the string inverter. The problem of shading and PV orientation is almost completely eliminated with microinverters on each panel. MPPT is done on the panel-level and added power gains are as high as 30% as compared to string inverters that executes MPPT on full array-level. Cost is not always the most important economic parameter for evaluating solar systems. See the link below for more info:
Thanks boss, but if you don't mind my asking... why will i use a "grid-tie" system to feed into an off-grid system, when a well setup off-grid system will do the job for me 100%. or am i missing something here?
Sir, if you read my previous postings, I have always emphasized 100% off-grid systems that are comprised of predominantly day-time AC loads. It may be an office or a business premise or even residential that require loads that run mostly in the day-time. Mind you, people have different solar power requirements, so don't restrict your understanding to only traditional dc-coupled residential off-grid systems.
In this type of off-grid system, the overall energy conversion efficiency is very high (in the high 90's) as energy from the panel only undergoes 1 conversion cycle (DC to AC only) and this energy is consumed as AC directly. Charge controllers are not required in this system.
In the traditional DC-coupled systems, which you may be very familiar with, you have DC to DC (charge controller), DC to battery (battery chemistry; very poor efficiency for lead-acid batteries) and DC to AC (Inverter) conversion. Energy is lost at every stage of conversion. Overall energy conversion efficiency for traditional dc-coupled systems is generally low.
In conclusion, my emphasis or talking point IS about harnessing the high energy conversion efficiency of grid-tie inverters AC-coupled to battery based bi-directional inverters for off-grid systems where the primary load is day-time AC loads.
The emphasis is here again GRID-TIE - . A simple google search will also take you to various manufacturers use of grid tie inverters recommendation and certifications for grid tie which specifically refers to connecting to local distribution grid
Please note that Grid tie inverters are not only frequency based control but they require a complex mechanism to detect abnormal grid conditions such as power swings and ramp rates which are different for every country . A grid tie inverter can also inject VAr into the system or disturb the static var compensations as well as contribute to harmonics.
Oga, again you are going off-point. Your emphasis is GRID-TIE in its legal sense while my emphasis is GRID-TIE IN OFF-GRID SYSTEMS. Why are we all going around the bush here?? Nigeria is not ready for legal grid-tie systems yet, I know all that bla bla bla. However, grid-tie inverters can be utilized (and is being utilized in Nigeria) in completely off-grid systems: There is no legal grid to back-feed into and there are no certifications to submit to the govt. regulating bodies. There is no "accidental" back-feed to the grid if the installer knows what he is doing. That will be as stupid as an installer connecting a battery-based inverter to a 230Vac local transmission line. Am very sure he will not survive the fire-works (...joke..). If you want to counter my arguments, let it be based on GRID-TIE IN 100% OFF-GRID SYSTEMS.
In addition, the overall efficiency of AC-coupled systems are much higher than DC-based systems because the conversion is DC to AC and your load is 100% day-time AC. The battery backup is just an add on feature.
Satellite TV Technology / Re: Solar Energy, A Complement To FTA by jazzman2(m): 12:37pm On Aug 27, 2019 
