Need help with wiring size and fuse/breaker size from array to inverter and from battery bank to inverter.

[Hedges]

Thanks for your help, but I’m stuck with a 24 V inverter that I just bought. I got a Victron 24 V inverter. So I’ll have to try to do what I posted with three strings and three charge controllers.
for me I have to keep it very simple, as I’m not as knowledgeable as most. Again thanks for all your help. ??

24V no problem, inverter and battery can be 24V.
Charge controller can be set for 24V (or maybe automatically detects 24V battery) as its output voltage.

What I'm saying is, for a 24V system, you should connect your PV panels as 48V or 72V. The charge controller will act like a transformer and drop that to 24V at higher amps and charge the battery.

The battery may range between 22V and 32V depending on depth of discharge/state of charge. And rate (current) of charge or discharge.

A "24V" PV panel may range between 27V and 45V depending on temperature and current draw. It requires a charge controller to regulate battery voltage, and MPPT charge controllers are particularly good and extracting maximum power over a wide temperature range. They also let you run higher voltages (more panels in series, fewer in parallel) so you can use smaller wires and sometimes no fuses. But a "24V" panel will not work very well to charge a 24 battery, at least not with an MPPT charge controller.

The drawing I gave you with four 12V panels and two 24V panels will work for you. It just leaves one 24V panel unused.
You can add to it. If you buy four more panels, 320W 24V, you can add those. Two in series for 640W 48V, add in parallel with the existing 48V strings. Do it again for another 640W 48V. Use a 15A fuse for every string, now for fuses in total.

4 x 150 = 600W
2 x 300 = 600W
2 x 320 = 640W
2 x 320 = 640W
(All are 48V nominal)
All of these strings connected in parallel and fed into the charge controller is:
600 + 600 + 640 + 640 = 2480W at 48V

They won't actually produce the full 2480W except on a cold bright day. More like 2000W most of the time.
The Renogy charge controller can't make use of all 2000W, so as the sun comes up, power will increase to 1500W and stay flat until later in the day.

But I have a way to avoid wasting any power.
Orient two of the strings at 10:00 AM sun.
Orient two of the strings at 4:00 PM sun.
Half the panels are now at a 90 degree orientation to the other half. They never make full power at the same time, but some make more early and some make more later.
This setup will have about 1600W of peak production on a cold sunny day, more like 1400W peak in normal weather. That is just under the Renogy's max output, so a single charge controller will handle all of them effectively.

 

[JonL]

Wow! Sounds interesting. But won’t all these parallel connections cause more heat, just what I’m trying to get away from by doing series parallel? Are you saying that they need to be in parallel to fit in one charge controller?

 

[snoobler]

JonL Please listen to Hedges. If he says something that contradicts something you think you understand, you're wrong. You have a LOT of the basics completely wrong and operate under a lot of incorrect assumptions.

 

[JonL]

How does one learn all these basics? ?

 

[JonL]

You have to remember that I am still new at this. It took me a while just to understand how electricity works, as I saw people putting bus bars and connecting all kinds of things to the bus bar. As I understood AC was moving electricity in back-and-forth directions, and DC moves in one direction. So I couldn’t figure out how the current could go in one direction with bus bars.
So if I’m going to take somebody’s advice when I’m way over my head, I don’t know what bus bars to use for the amount of amperage coming through my system, or even sure about what fuse I’m going to use.
I don’t want to burn down my house, so I’m taking it slow till I understand how everything works. Just like driving a car, you have to actually go out and do it and hopefully understand it well enough that you don’t get in an accident. Or learning from history or finance – baby steps!
You don’t climb a mountain the first time out! ?
Don’t get me wrong I appreciate all your saying, I’m sure you remember the first time you started learning about electricity.

 

[Hedges]

How does one learn all these basics? ?

Some of us started with hobby kits, or books. Sometimes high school physics, or junior college or Navy technician classes, or on-the-job.
I started in grammar school (mom provided books and kits for many areas of science and engineering). Lots of hobby projects, and went on to get a degree and work 40 years in this field. It goes much deeper than I know in some specialties, and there are some I'm skilled at.

By starting with low voltage and low current (meaning no lead-acid or lithium batteries, just flashlight batteries) you can experiment without getting hurt. Once you connect two "24V" PV panels in series or use a rechargeable battery, there is risk of shock or burn. Then you need to understand what can go wrong and avoid doing it. There is also possibility of equipment damage if you connect something backwards, or too high voltage, too much current.

There is so much out there (much of it for-profit) that it's hard to find something basic starting with batteries, volts, amps, switches and going through step by step. You can probably find tutorials and examples on line. Wikipedia has good explanations for each key point, once you identify a word/concept to understand.

On this site, Will has videos giving examples how to assemble and use PV equipment.

I like hands-on equipment with written workbooks, theory, and equations.

There are kits like this one, each designed around different specialties. I've seen microcontroller, motor circuits, transistors, etc.

POWER ELECTRONICS LAB : Power Electronics kit | TRIAC | UJT | DIAC

We Provide Application study of different types of POWER ELECTRONICS LAB and Devices i.e. thyristors (SCR, TRIAC, DIAC ) and MOSFET.

atechindia.com

You need the basics like volts adding in series, amps adding in parallel, current flowing in a circuit when it is connected in a loop, V = I x R, W = V x I, and so forth to calculate results.

 

[JonL]

Thanks, math was never my strong point and now I’m 63 so I’m late to the game. I have tried to watch Will Prowse videos, I picked up some stuff but a lot of it’s way over my head!
So thanks for your patience, as I stumble along! ?

 

[Hedges]

Most things like house wiring, we can turn off the main switch, check with a meter to make sure it is really off, do our work, step back and turn on the main switch.

With Solar, PV panels in the sun, and batteries, can't be turned off. So we have to work with them in a careful manner, knowing what to do to prevent damage or injury.

For cars, it is as simple as "remove negative cable from battery first". If you put a wrench on positive terminal first, it can touch the car body and short out the battery. Similar care is needed for working on Solar equipment.

 

[JonL]

Most things like house wiring, we can turn off the main switch, check with a meter to make sure it is really off, do our work, step back and turn on the main switch.

With Solar, PV panels in the sun, and batteries, can't be turned off. So we have to work with them in a careful manner, knowing what to do to prevent damage or injury.

For cars, it is as simple as "remove negative cable from battery first". If you put a wrench on positive terminal first, it can touch the car body and short out the battery. Similar care is needed for working on Solar equipment.

I just heard from Scotty- the car guy, that removing the negative cable on modern cars can screw up your computer chips. This works on older cars though. I think they make it so complex so you have to take it to a mechanic! ?

 

[Hedges]

Thanks, math was never my strong point and now I’m 63 so I’m late to the game. I have tried to watch Will Prowse videos, I picked up some stuff but a lot of it’s way over my head!
So thanks for your patience, as I stumble along! ?

OK, so you're only 4 years older than me, but I've been doing this stuff for 50+ years so far!

And I sometimes correct the "experts" (from the biggest companies and largest programs you've ever heard of) because they memorized things as a PhD but don't stop to think through whether what they were taught is being applied correctly.

For me, video (or lecture) is OK once for a demo, but I need written step-by-step instructions so I can read and do each step, back up and double-check.

 

[Hedges]

I just heard from Scotty- the car guy, that removing the negative cable on modern cars can screw up your computer chips. This works on older cars though. I think they make it so complex so you have to take it to a mechanic! ?

That generally gives the car amnesia. It is a simple way to reset OBD-II error codes. The car also will re-learn fuel and ignition timing and transmission shift points. Radio will forget station presets.

But for some cars, it will also forget who you are, and not open the door to let you in (electronic keyless entry and ignition.)

The electronic diagnosis equipment and smog-check systems require expensive updates every year for the latest models. This wasn't to help the mechanic, it was to make money for the vendor. Of course, the automakers primarily care about reducing manufacturing costs and complying with regulatory requirements so they're allowed to sell cars. Efficiency and pollution rules drive more sophisticated controls. But I do like how clean our air is, compared to the 1970's.

I got a $120 code reader from Harbor Freight. It'll tell me "cylinder #1 misfiring" or "Catalyst low efficiency" and provides real-time readings and graphs. Quite useful for working on my 20 year old cars.

I used to design computers (microprocessor chips inside HP computers, actually.) But I often have difficulty getting anything computerized to work well. Takes the right software to talk to it and debug, and things constantly change. I prefer to use DMM, relays, simple analog circuits. I stick with early models of electronic stuff that don't require a program running on Windows.

 

[JonL]

Awesome! My expertise comes in photography, you can find me on Instagram.
jonleachstreetphotos or jonleachphotography.com
I started doing this full time after 38 years at Boeing. I started with my first camera at 17.

 

[Hedges]

If you have two, 48V (nominal) strings of PV panels going to the Renogy charge controller, a 2:1 adapter like this (or a "Y" cable) could be used. or you could just cut an MC cable to make pigtails and connect them to the Renogy

Solar Panel Cable Connector MC-4T Branch Male and Female 1to2/3/4/5/6 Waterproof | eBay

One female to double male (F/M/M)and one male to double female (M/F/F). T Type MC-4 Male/Female Solar Panel Cable Connectors MC-4 T Type 3 branch Solar Panel Cable Photovoltaic Connectors MFFF FMMM IP65.

www.ebay.com

If you have four, 48V (nominal) strings, each one needs a fuse, 50A connectors like the 4:1 adapter would work, and you should use 8 awg to the charge controller:

Solar Panel Cable Connector MC-4T Branch Male and Female 1to2/3/4/5/6 Waterproof | eBay

One female to double male (F/M/M)and one male to double female (M/F/F). T Type MC-4 Male/Female Solar Panel Cable Connectors MC-4 T Type 3 branch Solar Panel Cable Photovoltaic Connectors MFFF FMMM IP65.

www.ebay.com

Pair Black+Red PC,Solar Panel wire 8 AWG with 4 Connectors (compatible with MC4) | eBay

Connectors are on both ends of the wire, Female/Male. Cables are UL listed, connectors are UR reconganized. Connectors spec. Assembly and located in Alpharetta, GA.

www.ebay.com

30A In-line Quick Release Fuse Holder Solar Panel Cable PV Connector 1000VDC | eBay

30A fuse embedded into a waterproof fuse holder, MC4 connector lead on each end. Rated Current: 30A. Insertion Force / Withdrawal Force: ≤50N / ≥50N. Designed to provide complete single circuit protection to your solar power array.

www.ebay.com

Put a 15A fuse in each of four fuse holders.

 

[John Frum]

And I sometimes correct the "experts" (from the biggest companies and largest programs you've ever heard of) because they memorized things as a PhD but don't stop to think through whether what they were taught is being applied correctly.

All the stuff that one learns during the steep part of the learning curve is less contextualized than the stuff that you learn later when you have a body of knowledge to collate against.
Stuff one learns as a child is often understood in a childish way unless its re-evaluated.

 

[Hedges]

Awesome! My expertise comes in photography, you can find me on Instagram.
jonleachstreetphotos or jonleachphotography.com
I started doing this full time after 38 years at Boeing. I started with my first camera at 17.

I drew schematics for image sensor and connector to put cameras in cell phones (the sophisticated part is the sensor IC and the software, which I didn't do)

I was aware of but didn't work directly on cameras used in aerospace for navigation by the stars.

I did test/characterization and debug of scientific cameras and images sensors, including radiation testing. Met with James Janesick (who designed camera for Hubble and wrote the book, literally, on image sensor characterization) for some training and a seminar he gave.

My only formal training in photography or cameras occurred in the 4th grade. We made a pinhole camera out of a shoebox and a piece of aluminum foil. Developed film in the darkroom.

Pinholes also work for things that aren't easy to focus with refractive lenses, like X-ray and neutron, so that was quite applicable for my later work. I put a piece of foil with pinhole over the image sensor and took a bad selfie to prove it was working. From image defects I identified a bug, tracked it down to error in FPGA code which was corrected.

I never cared much about photography, but took snapshots with a vintage camera I inherited and some newer ones. When it was my primary job for a year or so, I approached it as electronics (one photon, two photons ...)

 

[JonL]

I drew schematics for image sensor and connector to put cameras in cell phones (the sophisticated part is the sensor IC and the software, which I didn't do)

I was aware of but didn't work directly on cameras used in aerospace for navigation by the stars.

I did test/characterization and debug of scientific cameras and images sensors, including radiation testing. Met with James Janesick (who designed camera for Hubble and wrote the book, literally, on image sensor characterization) for some training and a seminar he gave.

My only formal training in photography or cameras occurred in the 4th grade. We made a pinhole camera out of a shoebox and a piece of aluminum foil. Developed film in the darkroom.

Pinholes also work for things that aren't easy to focus with refractive lenses, like X-ray and neutron, so that was quite applicable for my later work. I put a piece of foil with pinhole over the image sensor and took a bad selfie to prove it was working. From image defects I identified a bug, tracked it down to error in FPGA code which was corrected.

I never cared much about photography, but took snapshots with a vintage camera I inherited and some newer ones. When it was my primary job for a year or so, I approached it as electronics (one photon, two photons ...)

Well you’ve been in just about every kind of tech. I fumbled around in photography for years until I finally figured out I needed to go to school. So I took a couple of years and did studio lighting, Cibachrome and type C only to find out that it’s obsolete now. Did some fashion photography, zone system and some other artistic ventures.
After a while I knew I couldn’t make a living off of it, so hence the job at Boeing.
I even took an recording engineer in class, liked music enough to where I thought it would be fun. But nothing ever came from it as the technology I learned from was already 20 years old. Even learned how to play the guitar, but that faded in time.
I stumbled onto street photography after I retired, as I found Vivian Maier work and decided I’d give it a shot! there are so many really great nature photographers I figured I needed to try something else.
So here I am with solar and electricity. I guess I got interested because of Nikola Tesla. I had a fascination with his life. The power companies and bankers keep us from any alternative source except solar and wind.
I also study economics and history, you have to know some of this in order to not fall into complete poverty. At least I’m enjoying my retirement, a lot of people I know never got out of Boeing. Their health faded. I knew it was time for me to go, so I retired at 59 1/2. Never looked back!

 

[Hedges]

How does one learn all these basics? ?

Here's an idea:
You can download LTSPICE for free. I'm using it right now for work.

Draw a simple schematic with a 12V DC voltage source to represent a battery. A 10 ohm resistor to represent a load. Connect with wires. Add a ground on the negative side. set up transient simulation for one second. Plot voltage. Open a second plot window. Plot current.

Then you can change the voltage source to sine wave, and repeat.

Substitute inductor for resistor. Capacitor for resistor. Some will fail to execute, may need a resistor in series with inductor (which means if you put an inductor or transformer on a battery it would have burned up.)

Copy example circuits you see in Wikipedia or elsewhere to try them out.

You can play for free with simulations and not break anything.

 

[Cancerfood]

Can you guys help me figure out what size wire, breakers and fuses I need to install I've read and watched a lot of videos and I just can't figure out what all I need. I want to make sure I do it right the first time so I don't have any issues.

I have 24- Solar panels 260 watt VOC 37.9 v ISC 8.9 a

I have 2 Growatt SPF 3000 TL LVM 120V split phase 48V off grid inverters. The specs on them are Max PV array 4500W, battery voltage 48v dc, MPPT range 60Vdc to 115Vdc max pv open circuit voltage 145 vdc, max solar charge current 80A and AC charge current is 40A these specs are for each inverter

I have 2 - LFP 24V 5.63 kwh 220 Ah Battery Pack With BMS 130A LiFePO4

Items Parameters
Rated voltage 25.6V
Rated capacity 220Ah
Energy 5.632Wh
Maximum charge current 130A
Maximum discharge current 350A
Cell over discharge 2.5V
Cell over charge 3.65V
70-80% + capacity
Temperature protection 65℃
Battery chemistry - lithium iron phosphate (lifepo4)
Maximum discharging pick is 500 amp
BMS Included
Size Module: 380*197*475(mm) 11"H x 17" W x 22" D
73 kg - 161 Lbs

I have 2- midnight solar 6 pv combiner box with 20 amp breakers at each array before it heads inside to the inverters

I have a Anderson SB 175 to SB 175 Y Series cable 36" 24v to 48V 6 awg wire size

I have 2- DIGITAL LED DISPLAY GOLD 2 ANL FUSE HOLDER 1-0, 2- 4 GAUGE 100A fuse 1 for Positive and 1 for Negative

Hot rod, thanks for the level of detail you go into. It really help me to learn the pieces of your project. I am just curious why you are choosing to go with two growatt units instead of the single 12k growatt?

 

[hotrod]

Hot rod, thanks for the level of detail you go into. It really help me to learn the pieces of your project. I am just curious why you are choosing to go with two growatt units instead of the single 12k growatt?

Hi cancerfood since you sent me the message about why I went with the two 3kw growatts instead of the 1 12kw growatt I guess the reason was is because I didn't know they had a 12 kw off grid inverter and didn't have the funds at the time to go any bigger. After you sent me the message I did a little research on the growatt 12 kw inverter I really liked the specs on the inverter and also found out it is a low frequency inverter the 3kw growatts are high frequency inverters and only weight 25 lbs each the 12kw growatt weights 165 lbs. I have since traded the 2 3kw growatt inverters in on 1 of the 12kw growatt inverters. I'm glad you ask me about the inverter I think this inverter is going to do a much better job than the 2 smaller inverters. It came in this week and and I have that heavy sucker mounted and my dc side wired up. I hope to get the ac side wired up this week or next and hopefully get it turned on and producing some power.

 

[hotrod]

Much easier to digest. Thank you.

Need a few more details.

1) With two batteries and two inverters and two combiner boxes, do you essentially have two systems side-by-side, or are they paralleled?

Guessing:
2) 1 2S6P array into one growatt, the other 2S6P array into the other growatt.
3) Growatts working in parallel with each other to provide 6kW of 120V or 240V split phase output.
4) 2 batteries in parallel feeding both growatts or 1 battery each feeding one growatt?

5) I don't see how your array is configured, but I glean from the combiner box, you have a 2S6P X2 arrays with each array going into a combiner box. If you have 20A breakers for each two panels in series (6 breakers per combiner box), that's fine. If you have a single 20A breaker from each combiner box, that's not enough.

(6) Where is the Anderson?
(7) where are those 100A fuses?

Observations:

Battery:

11.26kWh of battery is a bit on the low side for 6240W of panels, but you're still well within the 130A charge limit on the batteries. The inverter manual recommends about 20kWh of battery for two inverters (probably assuming FLA/AGM batteries). This isn't really an issue, but the array is capable of about 30kWh of energy per day (assuming 5 hrs irradiance). If you plan to pull a lot of load only during solar hours with very low battery usage in non-solar periods, it should be great.

Inverters:

The Growatts are listed at 11.5kg for 3000W units. In comparison, my Victrons are 30kg for 4000W units (almost 3X the weight for 33% more power). Also, the Victron is ONLY an inverter/charger. It does not provide an integral solar controller. The quality of an inverter is proportional to its weight. The Growatts as combined units are very lightweight. I would be concerned about the longevity and surge capability of these units. If you only use them at under 2kW total, and you don't rely on the surge rating of the units, that would likely improve service life.

Hi snoobler since this post I have changed directions on my inverter, I traded in the 2 new off grid high frequency 3kw growatt inverters for 1 off grid low frequency 12kw growatt inverter. the 3kw units weighed 11.5 kg 25 lb each this 12kw inverter weighs 75 kg 165 lb this thing is heavy for sure, I got worried about the 2 smaller inverters not being able to run my pool pump and my air compressor and lights and what ever else I had on with out over loading and kicking off, so I decided to go bigger and go with a low frequency inverter before I used the 2 smaller ones and could still trade them in for new. I do have a question for you though, the 2 3kw units had a pv range of up to 145 vdc each so I had to wire each inverter with 12 260 watt panels with a voc voltage of 113.7 dc volts total 3S 4P each panel is 37.9 voc, this 12kw inverter has 2 mppt pv inputs and the book says it has a max pv open circuit voltage of 250vdc but it doesn't say if this is for each pv input or if it is a combined for both inputs do you know if it is for each string or both and if it is for each string would it be better to change to a 6S 2P configuration on each input string 24 panels total or just leave it the way it is.

This is the specs on the 12kw inverter
Specifications MODEL SPF 12000T DVM-MPV Battery voltage 48VDC INVERTER OUTPUT Rated Power 12KW Surge Rating (20ms) 36KW Waveform Pure sine wave/ same as input (bypass mode) Nominal Output Voltage 104V-110V-115V-120Vac / 208V-220V-230V-240Vac(+/-10% RMS) Output Frequency 50Hz/60Hz（+/-0.3 Hz） Inverter Efficiency(Peak) >85% Line Mode Efficiency >95% Power Factor 1.0 SOLAR CHARGER Maximum PV Charge Current 80A 120A DC Voltage 48V Maximum PV Array Power 7000W MPPT Operating Voltage(VDC) 60-245V Max. PV Array Open Circuit Voltage 250VDC Maximum Efficiency >98% DC Input Low DC Cut-Off Voltage (Only Lead Acid) @load<20%: 42.0V; @20%≤load<50%: 40.8V; @load≥50%: 38.4V Low DC Warning Voltage (Only Lead Acid) @load<20%: 44.0V; @20%≤load<50%: 42.8V; @load≥50%: 40.4V Low DC Warning Return Voltage (Only Lead Acid) 48V Low DC Warning SOC (Only Li) Low DC Cut-off Soc +5% Low DC Warning Return SOC (Only Li） Low DC Cut-off Soc +15% Low DC Cut-off SOC (Only Li) Default 20%, 5%~50% Settable Cold Start SOC (Only Li) >Cut-off Soc+10% High DC Recovery Voltage 58VDC High DC Cut-Off Voltage AGM:60V, FLD:62V, USE or Li Mode: C.V. Voltage + 4.0V AC INPUT Voltage 230VAC Selectable Voltage Range 154~272VAC(for appliances ), 184~272VAC(for UPS) Frequency Range 50Hz/60Hz (Auto sensing) Maximum Charge Current 120A BYPASS & PROTECTION（Grid & Generator） Typical Transfer Time 10ms(max) Overload Protection (SMPS Load) Circuit breaker Output Short Circuit Protection Circuit breaker MECHANICAL SPECIFICATIONS Dimensions (W*H*D) 650*380*225mm Net Weight (Solar CHG) kg 75 OPERATING ENVIRONMENT Operation Temperature Range 0°C to 40°C Storage Temperature -15°C to 60°C