# Will I have enough Amps?

Solar Expert Posts: 49 ✭✭
Running a Midnite 150 at 24 volts along with the Panels at 24 volts.... array current is 24.15 total watts is 870. Would this be enough to charge a 24 volt battery bank consisting of 6-6 volt batteries??

Joe
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• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?

Not enough information, Joe. And some of it is wrong: you can not make a 24 Volt battery bank using six 6 Volt batteries. You can do it with four or eight, but not six.

Anyway, 870 Watts of panel through a MidNite Classic 150 should get you about 28 Amps peak current on a good day.

I have 700 Watts of panel and can get 25 Amps on my 24 Volt bank, which is one string of four 232 Amp hour 6 Volts.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

Your right! I didn't think this out very well. All this is just theroy at this point. Right now I have 580 watts in panels at 16.1 amps. Two more will make 870 watts at 24.15 amps which I want to do at a later time. So I should have said will 16.1 amps (max) charge 4- 6 volt battery bank wired at 24 volts. I'm trying to plan ahead and go with a 24 volt inverter but right now I want to be able to use the system I have. Don't want to buy twice if can be helped. I just don't think 16.1 amps is enough to charge a 24 volt battery bank??? They will be 220ah batteries.

Joe
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?

Math time!
16 Amps * 100 / 220 Amp hours = 7% peak charge rate.

But 580 Watts on an MPPT controller should give you a couple Amps more than 16. The extra Voltage is converted to additional charging current. The formula looks something like this:
Panel Watts * efficiency (panels + controller, usually 77%) / minimum charge Voltage (usually system nominal) = peak current potential. Or for 580 Watts on a 24 Volt system about 18 Amps. Your actual numbers may vary of course.

Providing the loads running at the time of charging don't drag that 7% (or 8%) rate down below 5% it will work.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

You know your stuff:D Thanks for that. May I indulge and ask another question or two. First. With the sun shinning, How do I make the connections in the box with hot wires. Positive first than negative or do I just throw a blanket over the panels and wire them that way. I don't want to have a arc ruining the panels. Second. I have been looking at the Pro Watt 2000 inverter. I like it because it is prue sine wave. Just 12 volts though. The specs on it say 162 amps input max. With the bateries I plan on using if I go with 12 volt bank..Two 6 volt in series than parallel... I'm confused. What do they mean by 162 amps max input for the inverter? The battery specs say 220 ah....Min @ 75 amps:100, Min @ 25 amps: 425. I plan on using 4 bateries to start. Will this inverter match these bateries?? I have a lot to learn about D/C
• Banned Posts: 1,807 ✭✭
Re: Will I have enough Amps?

It's best to cover the panels. I don't know what input voltage you're running on your Classic, but high voltage DC is very dangerous - more dangerous than AC at the same voltage. 12 volt is not usually enough potential to cause electric shock. 24 volt can make you speak in tongues if the system is running at 30 volts and the electricity flows thru the moisture in your body to ground. 48 volts and above will lay you out deader than a stone.

It only takes 10 milliamps of current flowing thru the heart to kill a person. DC power causes your muscles to contract and you can't let go when you come in contact with it. AC power causes muscles to contract and expand and it usually throws a person clear. So if you're running a Classic 150 with solar panels at 50-150 volts, treat the input power to that controller with as much respect as you would wiring up a household 120 volt outlet with the wires hot.
--
Chris
• Solar Expert Posts: 5,804 ✭✭✭✭✭
Re: Will I have enough Amps?
Joe J wrote: »
Running a Midnite 150 at 24 volts along with the Panels at 24 volts.... array current is 24.15 total watts is 870. Would this be enough to charge a 24 volt battery bank consisting of 6-6 volt batteries??

So Lots of questions, and lots of this appears hypothetical?

What panels do you have now? How are they wired? if you have 24V panels that are not in the 35 volt VMP range and they are connected in parralel to the Classic 150, they will NOT charge a 24V battery bank properly.

The added panels need to match what you have, so if you have 4 - 145watt panels bought from Amazon and your adding 2 more of the same panels, and they are connected 2 in series currently and you currently have 2 strings and your adding another string of the same panels, first you'll need to add a combiner box to your system or reconfigure the panels to be in strings of 3 so you have just 2 strings and one can't over power the other...

If they are currently connected in a string of 4 that would be another matter. If you just wanted to add them to the string you would want to check that the VOC isn't too high, Midnite has a nice sizing chart here.

You will have a battery bank of 4 - 6volt 220 Amp hour(Ah) batteries for a battery bank of 24Volts at 220 Ah. You would want to charge this at 5-13% (C20 - C8 ) or (1/20 x 220=) 11 Amps to (1/8 x 220=) 27.5 Amps. 870 watts of panels through an MPPT charge controller should produce roughly 870Watts / 24V = 36.25Amps x .8 (80% derating)= 29 Amps that should be fine.

None of this takes into account what loads you have or if you have enough direct sunlight to recharge them depending on your use...
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 5,804 ✭✭✭✭✭
Re: Will I have enough Amps?
Joe J wrote: »
I don't want to have a arc ruining the panels. :
Shorting panels should not harm them, much depends on how you will have these panels connected see my post above, if you have them wired into a combiner box it is nice to have an array disconnect or breaker at your Charge controller(CC). if you already have this flip the breaker install the panels change the configuration if you need to on the CC and throw the breaker.
Joe J wrote: »
Second. I have been looking at the Pro Watt 2000 inverter. I like it because it is prue sine wave. Just 12 volts though. The specs on it say 162 amps input max. With the bateries I plan on using if I go with 12 volt bank..Two 6 volt in series than parallel... I'm confused. What do they mean by 162 amps max input for the inverter? The battery specs say 220 ah....Min @ 75 amps:100, Min @ 25 amps: 425. I plan on using 4 bateries to start. Will this inverter match these bateries?? I have a lot to learn about D/C

The 162 Amps is based on the most current it will draw 12V x 162Amps = 1944 Watts (or a 2000watt inverter) if it was more truthful it should have the capacity to draw up to it's peak rate at any point in time times it's low current shut of so if it has a peak rating of 3600 watts and has a shut off of 11volts - 3600W/11V or about 325 Amps!!! Lots of current so you will need big wires!
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Solar Expert Posts: 3,741 ✭✭✭✭
Re: Will I have enough Amps?
Joe J wrote: »
With the sun shinning, How do I make the connections in the box with hot wires. Positive first than negative or do I just throw a blanket over the panels and wire them that way. I don't want to have a arc ruining the panels.

The arc won't ruin your panels. It will ruin you and your connectors. I suggest that you buy a Midnite combiner box with circuit breakers and built in MC4 connectors. Mount the box, wire it to your controller, flip off the breakers in the combiner, plug in the panels, flip the breakers back on, done.

--vtMaps
4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?
Photowhit wrote: »

The added panels need to match what you have, so if you have 4 - 145watt panels bought from Amazon and your adding 2 more of the same panels, and they are connected 2 in series currently and you currently have 2 strings and your adding another string of the same panels, first you'll need to add a combiner box to your system or reconfigure the panels to be in strings of 3 so you have just 2 strings and one can't over power the other...

Yes, this is the case. Right now I have only 4- 12 volt panels each rated at vmp 18 volts, imp 8.05. I planed to run them in 2 strings with a combiner box/breaker box than add another string at a later date. So form your statement I would have to go 6 panels from the start to do the job for a 24 volt battery bank. Correct? Buying two more panels if I must is not a problem. At this point nothing is hooked up so I can wire it anyway that is best. I have also been struggling over a 12 volt battery bank with a prue sine wave inverter Vs 24 volt battery bank with a modified sine wave inverter. Is it worth staying at a 12 volt battery bank for the prue sine wave inverter? Would a modified sine wave inverter make clean enough power that will run most things? What do most people do? (don't wnat to spend the money for a prue sine wave inverter at 24 volts)

Joe
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?
Joe J wrote: »
Yes, this is the case. Right now I have only 4- 12 volt panels each rated at vmp 18 volts, imp 8.05. I planed to run them in 2 strings with a combiner box/breaker box than add another string at a later date. So form your statement I would have to go 6 panels from the start to do the job for a 24 volt battery bank. Correct? Buying two more panels if I must is not a problem. At this point nothing is hooked up so I can wire it anyway that is best. I have also been struggling over a 12 volt battery bank with a prue sine wave inverter Vs 24 volt battery bank with a modified sine wave inverter. Is it worth staying at a 12 volt battery bank for the prue sine wave inverter? Would a modified sine wave inverter make clean enough power that will run most things? What do most people do? (don't wnat to spend the money for a prue sine wave inverter at 24 volts)

Joe

This is what's known as "Ready, Fire, Aim!" Normally you figure out what you need/want to run then design the system to power it. Doing it 'backwards' gives you headaches like this.
I wouldn't buy a MSW inverter anymore; I just don't see the point. There are things they won't run and other things they won't run well and who wants to play that guessing game with their stuff?
Whether you pick 12 or 24 Volts really depends on how large the biggest (total) load is and how much capacity (Watt hours) you need to store. The more power needed, the better it is to go with higher system Voltage. Since you don't know how much power is needed you're in decision limbo. One way to look at it: a typical household outlet is 15 Amps @ 120 Volts or 1800 Watts. Most of the time it is no place near full capacity. Now doesn't that sound like a 2kW inverter? So if all you've got you'd plug in to one outlet the 2kW 12 Volt pure sine would work fine.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

Your totally right. I'm flying by the seat of my pants! I started this little project for a 12 volt light or two and a small Ham radio in case of an emergency with a small panel. That was it. But you know how things go. It got a little out of hand. I did buy a "Kill A Watt" meter but even than I'm not sure what the load will be because I'm not sure what I want to hook up. At that point I should have taken pencil in hand and figured out more of what I needed. But there's one thing I do know for sure, there are a lot of great people on this forum! I have learned a lot from all you guys in just a few posts! No judging just people who want to help. Can't beat that.

Joe
• Solar Expert Posts: 5,804 ✭✭✭✭✭
Re: Will I have enough Amps?
Joe J wrote: »
Yes, this is the case. Right now I have only 4- 12 volt panels each rated at vmp 18 volts, imp 8.05. I planed to run them in 2 strings with a combiner box/breaker box than add another string at a later date.
They are designed to charge 12 volt batteries with a PWM Charge Controller(CC) they have a high enough VMP. So if your using a PWM controller you should use single panels parralelled for 12V charging or strings of 2 for 24V charging. With an MPPT type CC you could do strings up to the VOC capacity of the CC for your coldest winter day.
Joe J wrote: »
So from your statement I would have to go 6 panels from the start to do the job for a 24 volt battery bank. Correct?
No That was based on my thinking they had a VMP of 24V and a 24V system and you wanting to add 2 panels to the system
Joe J wrote: »
Buying two more panels if I must is not a problem. At this point nothing is hooked up so I can wire it anyway that is best. I have also been struggling over a 12 volt battery bank with a prue sine wave inverter Vs 24 volt battery bank with a modified sine wave inverter. Is it worth staying at a 12 volt battery bank for the prue sine wave inverter? Would a modified sine wave inverter make clean enough power that will run most things? What do most people do? (don't wnat to spend the money for a prue sine wave inverter at 24 volts)

I'm leaning more toward suggesting a true sine wave inverter these days, I started with a Modified Sine Wave inverter (MSW) and really didn't find I had a problem running anything. Some people get a buzz from compact florescent lights which I didn't experience. some say not to run even laptops on them, but 99% of those car AC converters are MSW and people don't seem to have a lot of problems with them. I did check about my Dewalt battery charger and found that models after 2000 were fine on MSW but earlier ones fried, with a true sine wave you don't need to check every thing, just plug and play...
Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?

It also has to be pointed out that there are differences in MSW inverters: some have a better output waveform than others. But since they won't give you a picture of it or even a THD number you're gambling without any first-hand knowledge of the particular unit. Meanwhile pure sine inverters have come down in price quite a bit. This helps combat the 'sucker' advertising used by some makers like "3000 Watts for only \$XXX!" More Watts for the same/less money is not necessarily a bargain. There are some pretty lousy inverters available out there.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?
Since you don't know how much power is needed you're in decision limbo. One way to look at it: a typical household outlet is 15 Amps @ 120 Volts or 1800 Watts. Most of the time it is no place near full capacity. Now doesn't that sound like a 2kW inverter? So if all you've got you'd plug in to one outlet the 2kW 12 Volt pure sine would work fine.

Back in A/C land. Puts things into perspective for me. So it seems to be working out for my needs/situation to go with the Xantrex Pro Watt 12 volt PSW inverter, Midnite 150, 4 up to 8 panels with a 12 volt battery bank. The bank will consist of 4 golf cart batteries. I'm going to wire them 2 in series than 2 in parallel. The panels will be wired the same 2 to 4 strings in series than to parallel to a combiner box. (not counting fuses or breakers) O.K So far? If I wanted to go 10 panels or more I would have to go to a straight 24 volt system.
To add more storage capacity to the 12 volt battery bank say another 2 batteries (6 total) I would just continual wiring them in parallel. How I'm I doing? Thumbs up or down
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?

The four GC batteries is a good limit for a 12 Volt system: 440 Amp hours @ 12 Volts, about 1kW hour AC. If you try to add more batteries you will run in to the possible current sharing troubles found with multiple parallel connections. See the Smart Gauge diagrams: http://www.smartgauge.co.uk/batt_con.html
When or if you think you need more stored capacity you can either use larger battery size (like 320 Amp hour L16's) or increase the system Voltage.

If you want to go with the 10% middle-of-the-road charge rate that would be 44 Amps peak charging current which would require around 685 Watts of panel.
If you wire your panels as two parallel strings of two in series you will not need fuses/breakers on the panel strings.

So far, so good.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

With 4 panels I would have 40.3 amps and 580 watts. With 6 panels I would have 60.4 battery charging current and 870 watts. I'm going to go with 6 panels because I already have the rail space on the roof :-) I planed to run separate breakers for each string but you say I don't need them? Why is this? With 6 panels the amperage is 24.15 amps total. So I was thinking of a 30 amp breaker at the end of the parallel run another 100 amp one at the CC to battery and a 250 amp between the inverter and the batteries . The way I look at it is I don't think it will take much to kill this technical electrical stuff made today. I believe for the most part the fuses/breakers are there to protect the wire/cabling for fire.

Joe
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?
Joe J wrote: »
With 4 panels I would have 40.3 amps and 580 watts. With 6 panels I would have 60.4 battery charging current and 870 watts. I'm going to go with 6 panels because I already have the rail space on the roof :-) I planed to run separate breakers for each string but you say I don't need them? Why is this? With 6 panels the amperage is 24.15 amps total. So I was thinking of a 30 amp breaker at the end of the parallel run another 100 amp one at the CC to battery and a 250 amp between the inverter and the batteries . The way I look at it is I don't think it will take much to kill this technical electrical stuff made today. I believe for the most part the fuses/breakers are there to protect the wire/cabling for fire.

Joe

You do not need separate breakers for two strings; three or more and you do. It's a matter of "what happens if one string shorts?" The answer is it can take full Isc from an identical string, but not 2X (or more).
If you use three parallel strings you must protect each one (the panels should have a rating for it in their specifications - usually 10 Amps). You don't need an additional circuit breaker on the combined output feeding the charge controller, but it is handy as a shut-off and there is the possibility the controller itself might short internally which with enough panel on it could cause more than just the magic smoke to come out.
The output of the charge controller should be wired and protected according to its maximum output current, even if you aren't going to use it at that rate. This is really to protect it the other way 'round; the batteries can dump a lot of current back through the wire should the controller fail for any reason.
The inverter is another case of using the right wire size and circuit protection for the particular unit. Again the manufacturer should supply this info: something like "use a 'X' Amp fuse/breaker" somewhere in the installation instructions if not the specifications. They will also have recommendations for wire size which will vary according to length. A 2kW 12 Volt inverter will normally operate at less than 167 Amps, but if you allow for the lowest possible battery Voltage it could go up to 200 Amps which is usually the recommended fuse size. The surge rating doesn't have much bearing on this as that is momentary, not constant, and the wires & circuit protection should be able to stand the increased current for that time.
The NEC regs require the circuit protection to be sized as current * 1.25 * 1.25. Works fine in a constant Voltage circuit. For solar installs it's better to go by what the equipment makers recommend.
You can use smaller than maximum wire and circuit protection if you know you will never need the limit, but never reduce the wire size only!
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

O.K. I guess you would have to put the protection up on the roof to work best close to the panels. I was thinking about 2 strings of 3 - 36 volts as photwhit suggested. Than I wouldn't have to protect the individual panels and just put a shut off or breaker at the end of the parallel line coming into the house. Is this an option? Is there any benefit to this excluding not having to protect each individual panel? What would this do to the rest of my numbers?? Will it work with the 12 volt battery bank or be pretty inefficient even with the Midnite CC?
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?

It is not necessary to put string protection close to the panels, just before they are combined. Usually this is done near the array to shorten the wire runs to the combiner. But some people have run separate lines from each string in to the house where they put the breakers and tie the strings together right next to the charge controller.
Two strings of three in series will work fine.
There would be a benefit if you had a particularly long wire run: less V-drop and thus power loss.
Since you are feeding an MPPt controller as far as the output is concerned it doesn't matter which way you configure the array.
There is not going to be a significant difference in controller efficiency between a 36 Volt array charging a 12 Volt bank and a 24 Volt array charging the same bank. The whole efficiency curve from nominal system Voltage to V-max in is under 10% difference from one end to the other. This does get to be a consideration when the array Voltage goes very high in respect to the system. 3X isn't going to cause a problem. But imagine if the array were 120 Vmp; that's 10 times the system nominal. There you would be seeing the conversion efficiency affect over-all power.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

"Than I wouldn't have to protect the individual panels and just put a shut off or breaker at the end of the parallel line coming into the house". This statement is correct than right? Also, I could use a smaller gauge parallel wire coming into the CC?? With the 24 volt panel set up it gave me a 24.15 amp PV array current with six panels. With the 36 volt set up it comes out to 16.1 amp PV array current with six panels. I have a 25 foot run all total (unless I went though the roof) into the house. So where's the downside? Seems to good to be true.......But I'm liking it!
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?
Joe J wrote: »
"Than I wouldn't have to protect the individual panels and just put a shut off or breaker at the end of the parallel line coming into the house". This statement is correct than right?

Yes; only two parallel strings so individual string protection is not required.
Also, I could use a smaller gauge parallel wire coming into the CC?? With the 24 volt panel set up it gave me a 24.15 amp PV array current with six panels. With the 36 volt set up it comes out to 16.1 amp PV array current with six panels. I have a 25 foot run all total (unless I went though the roof) into the house. So where's the downside? Seems to good to be true.......But I'm liking it!

You're increasing the Voltage but not changing the current (because you are adding one panel on the end of each string, not reconfiguring the array ratio). The current from three in series is the same as from two in series. The wire has to be large enough to handle that current (times the two strings in parallel). What you change is the V-drop percentage, with a gain in output power. Don't confuse the current from the panels with the charge controller's output current. The first is a function of panel Imp, the second a function of the controller's MPPT action on the total array Watts.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

I'm getting a great education. So I would figure on 32.2 amp for the parallel wires into the house. Off the top of my head I'm thinking 8 gauge wire for D/C at 25 feet. What size breaker would you use coming in?

Just talking out loud here.....If I use this 32 volt configuration and stick with the 12 volt battery bank I can use a max of 9 panels in 3 parallel strings with the Midnite 150. Than of coarse I would have to protect each panel. If I went back to 2 in series and went to 4 parallel strings for a total of 8 panels (protecting each panel) again staying with a 12 volt battery bank for the four 6 volt GC batteries..... I'm wondering if 8 or 9 panels is just overkill. I know..... it also depends on the load........
• Banned Posts: 17,615 ✭✭
Re: Will I have enough Amps?
Joe J wrote: »
I'm getting a great education. So I would figure on 32.2 amp for the parallel wires into the house. Off the top of my head I'm thinking 8 gauge wire for D/C at 25 feet. What size breaker would you use coming in?

Let's just check 'cause I answer a lot of similar system questions.
You are talking about two parallel strings of three in series. The panels are 145 Watts each? The Vmp is 18-ish and the Imp is 8-ish? The total array would have a Vmp of 54 and an Imp of 16. The current only increases with each parallel connection. The Voltage only increases with each series connection. Over 60 feet 10 AWG would handle that. It would be on a 25 Amp breaker.
Just talking out loud here.....If I use this 32 volt configuration and stick with the 12 volt battery bank I can use a max of 9 panels in 3 parallel strings with the Midnite 150. Than of coarse I would have to protect each panel. If I went back to 2 in series and went to 4 parallel strings for a total of 8 panels (protecting each panel) again staying with a 12 volt battery bank for the four 6 volt GC batteries..... I'm wondering if 8 or 9 panels is just overkill. I know..... it also depends on the load........

The maximum output of the 150 on a 12 Volt system is 96 Amps, but I believe it requires a derating which makes 80 Amps the top (not sure). That basically means you could use up to about 1200 Watt array, however you slice it. That would be eight 145 Watt panels approximately. It would probably take nine, but you should check that with MidNite's sizing tool.

Now is there any point in having 80 Amps of peak charge current for a 440 Amp hour battery bank? No, not really. Better charging on cloudy days. Very fast (perhaps too fast) charging on sunny days. Good power available if the panels get really hot. Whopping huge amounts of Voltage if they get really cold.

And of course you'd either have to rip all the wiring out and change it later when you add all these panels, or put in the big wire now. Three parallel strings would be 24-ish Amps and require 8 AWG wire instead of 10 AWG.

This is why we say you need to plan a system based on loads. That will determine the system Voltage and size of battery bank. The panels and controller are there to recharge the batteries.
It is also why we say it's tough to expand a system. That nine panel array could put out 40 Amps on a 24 Volt system, which would operate somewhat more efficiently and be able to handle larger loads with less current. The more power that is current means more power turning into heat rather than work.
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Will I have enough Amps?

joej,
you are probably still confused on much of this, but if you want 6 pvs you can put 3 pvs in series and parallel another 3 pvs in series. this means you have 2 strings of 3 and will still be fine without a fuse or breaker for each string. if you want 3 strings with 2 in series then this requires the fusing or breakers because something going wrong on one of the strings or even 1 string wired in backwards would force the power of the 2 other strings through it and blow out that string without the protection of a fuse or breaker for each of those strings.

i'll take this further as you asked of 9 pvs to use and this can't be evenly distributed in 2 strings so it would look like 3 strings of 3 to make it work and each string will be fused/breakered. that amounts to 3 fuses/breakers. now if you had an even number like 8 it could be 2 strings of 4 in series and no fusing/breakers required under this arrangement. the voltage will be higher on each string, but this isn't a major problem as the classic will take that higher voltage safely and downconvert it to your 12v battery bank requirement. the vmp on each string will be around 72ish volts with a voc near 90v.

now for 10 pvs can this go to 2 strings of 5 in series you may ask? yes. 2 strings of 6? yes. (note here that the current would clamp backward to the current limitation of the cc and this was referrenced to illustrate the pv arrangement) the controller can handle it that high, but you have to watch when voltages go high so as to not go beyond the working voltage of the cc. this cc has a protection of going beyond 150v, but you still may not want to put it that high as when the protection (hypervoc) is active there isn't any power being realized as the classic is shutdown.

the higher operating voltage from the pvs will lower the losses over the wire run to the classic, but the high input to output ratio will cause the classic to be less efficient too. this is pretty much a wash for the record so it gives you options on the number of pvs to use without the need to have the fuses/breakers.

there is often a fuse or breaker to the input of the cc and that is fine as you can use it as a disconnect. there won't need to be any at the combiner if kept to 2 strings.

i hope this clears up some confusion.
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

So now I'm thinking the 2 parallel strings with 3 panels in series. Makes it easy not having to fuse each panel. Run a bigger gauge wire to eventually handle 9 panels if need be just in case. Later could always convert to a 24 volt battery bank and inverter. Yes, the Midnite 150 CC can handle 9 panels at 1305 watts, 8 with 1160 watts and 6 with 870 watts. The 6 panel layout might be a better match for my 12 volt 440ah batteries after reading your last post. Later on I can decide to go with a 8 or 9 panel setup 24 volt bank if need be but a I'll run the bigger gauge wire now just in case. Also, after the 4 battery setup I might look into using 6 batteries with the 12 volt system may not be ideal as you stated but I think the bigger "nighttime" capacity would be worth it?
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

Thanks Niel. I have been running Cariboocoot though the ringer today.
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Will I have enough Amps?
Joe J wrote: »
So now I'm thinking the 2 parallel strings with 3 panels in series. Makes it easy not having to fuse each panel. (note that each pv does not need to be fused anyway as it is only each string that gets one) Run a bigger gauge wire to eventually handle 9 panels if need be just in case. (note that increasing the voltage does not necessitate bigger wires as the current stays the same. in fact, the overall % of v drop loss becomes smaller with higher voltages) Later could always convert to a 24 volt battery bank and inverter. Yes, the Midnite 150 CC can handle 9 panels at 1305 watts, 8 with 1160 watts and 6 with 870 watts. The 6 panel layout might be a better match for my 12 volt 440ah batteries after reading your last post. Later on I can decide to go with a 8 or 9 panel setup 24 volt bank if need be but a I'll run the bigger gauge wire now just in case. Also, after the 4 battery setup I might look into using 6 batteries with the 12 volt system may not be ideal as you stated but I think the bigger "nighttime" capacity would be worth it?

i bolded my comments where applicable, but if you insist on many 12v batteries you will need to make the wires larger for battery interconnections and keep them identical lengths. method 3 in the link is good to use.
http://www.smartgauge.co.uk/batt_con.html
• Solar Expert Posts: 49 ✭✭
Re: Will I have enough Amps?

Got it Niel. Starting to get punch drunk with all the info I got today. I will re-read most of this in the morning. Wait I have rails to connect on the roof in the morning and mount the 4 panels I have. Wating for 2 more to come in. Almost forgot;)
• Solar Expert Posts: 10,300 ✭✭✭✭
Re: Will I have enough Amps?

no problem joe.

you could temporarily wire the 4 pvs as 2 strings of 2 in series until the other 2 come in and then just put another pv inline with each string making it 2 strings of 3 pvs when they do come in. if you are confused then wait until they others come in to do the final wiring.
• Solar Expert Posts: 3,741 ✭✭✭✭
Re: Will I have enough Amps?

Joe, I just reread this thread and you are considering whether to combine the strings on the roof (one pair of wires to inverter) or at the inverter (two pairs of wires to the inverter).

You should consider lightning and grounding when you make this decision. I prefer to see a combiner box with a lightning arrester outside the house and a heavy wire (also outside the house) to the ground rod.

--vtMaps
4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i