Advice of setup

[wlyt2000]

Hi all,

I have an existing setup and I an considering replacing the charge controller with MidNite Solar Classic 150 to harvest more energy.

My current setup is 1480W arranged in 24V, and batteries are also 24V. The panels are all 12V types, and a mix of 100W, 140W and 150W panels.
I may add another 900W of panels (all 150W x 6, Poly). I use the system to power 12V devices - lights, fans, routers etc. I downconvert my 24V to 12V.

The current batteries are 1000AH. Consist of 100AH SLA and there are 10 of them.


With the Classic, I plan put the panels in series - say 72V or 48V. and the batteries remains at 24V. Any advice here?

Also, I know I need to add VDC breakers for safety - where should I add? Any advice here?

THANKS.

[TomW]

I see one "gotcha" in your plan. Maybe you know this?

If you mix different wattage 12 volt nominal panels in series you will get the current (amps) of the lowest rated panel. This will cripple your maximum output severely.

At first glance without specific details  of all of the panels it is tough to determine if you will be able to add a Classic and see more power.

Just an easy on the math example:

4 nominal 12 volt panels one each 12, 24, 36 and 48 watts In a perfect world these would produce 1, 2, 3 and 4 amps @12 volts each.

All in parallel to the battery will make 120 watts if my math is right. Put these same 4 panels in series for 48 volts into The Classic and suddenly your 120 watts just became 48 watts (1 amp times 48 volts).

If that makes sense? Pretty basic electricity 101 stuff.

And, no, you can't just run them all into The Classic @12 volts nominal.

Tom

[zoneblue]

Systems over 400W are generally always better done with mppt. 

As tom said, so long as you use strings of the same Imp (or very near) you can add those panels to a mppt setup just fine. At 24v a classic 150 is good for around 2400W of solar, or in an overpanelled setup somewhere around 2800W. For 24V try to keep your strings in the Vmp range between 48-90V, ideally, although other voltages can be made to work, its just less efficient.

But as your system has a few other issues, youll benefit from raising a thread over at the naws forum to iron those out.

[wlyt2000]

Hi all,

Thanks to Zoneblue and Tomw. My 6 panels of poly 150W has arrived. It gave me a new idea. How best to setup if I have this:
1) 6 panels of 150W @ 12V Poly type. Specs is Pmax=150W, Vmp=18v, Voc=22.3V, Imp=8.43A, Isc=8.97A, Max System voltage V=1000VD, Fuse=10A
2) 4 panels of 150W @ 12V Mono type. Spec is Pmax=150W, Imp=8.22A, Vmp=18.25V, Isc=8.87A, Voc=22.45V. Max system voltage is 1000VDC.

The temperature of above test is AM=1.5, E=1000W/m2, Tc=25 deg celcius.
But my home roof temp is 25 at night and day time is 34 deg celcius mostly.


How do I make use of the 12 150W mix of panels - hopefully with Midnight classic 150.

The rest of my 100W and 130W - I am thinking of just do 12V in parallel into a Grid tie inverter since i got quite a lot of sunshine here.

THANKS for advice....

[vtmaps]

My 6 panels of poly 150W has arrived. It gave me a new idea. How best to setup if I have this:
1) 6 panels of 150W @ 12V Poly type. Specs is Pmax=150W, Vmp=18v, Voc=22.3V, Imp=8.43A, Isc=8.97A, Max System voltage V=1000VD, Fuse=10A
2) 4 panels of 150W @ 12V Mono type. Spec is Pmax=150W, Imp=8.22A, Vmp=18.25V, Isc=8.87A, Voc=22.45V. Max system voltage is 1000VDC.

How do I make use of the 12 150W mix of panels - hopefully with Midnight classic 150.

You have 6 new polys and 4 old monos.  And you want to know how to configure the 12 panels?

Tell me how many panels you really have and i will recommend a configuration. 

The specs on the two types of panels are close enough to use together.  If you do have 12 panels, I would recommend 4 strings with 3 panels (in series) in each string.

--vtMaps

[wlyt2000]

My 6 panels of poly 150W has arrived. It gave me a new idea. How best to setup if I have this:
1) 6 panels of 150W @ 12V Poly type. Specs is Pmax=150W, Vmp=18v, Voc=22.3V, Imp=8.43A, Isc=8.97A, Max System voltage V=1000VD, Fuse=10A
2) 4 panels of 150W @ 12V Mono type. Spec is Pmax=150W, Imp=8.22A, Vmp=18.25V, Isc=8.87A, Voc=22.45V. Max system voltage is 1000VDC.

How do I make use of the 12 150W mix of panels - hopefully with Midnight classic 150.

You have 6 new polys and 4 old monos.  And you want to know how to configure the 12 panels?

Tell me how many panels you really have and i will recommend a configuration. 

The specs on the two types of panels are close enough to use together.  If you do have 12 panels, I would recommend 4 strings with 3 panels (in series) in each string.

--vtMaps

My 150W panels are mentioned above. The remaining are a mix that I bought over time and a mix of 100W to 130W and even 140W. Also a mix of poly and mono. I am not good with Solar calculations and is learning and started out as an experiment and it slowly grew. But i figured better setup nicely to harvest more. And I suspect my current MPPT is not efficient and the way I design can be improved.

Is it if the Imp are very close then I can just put them in series and then parallel them of equal volts. Like 36V made of the recommendations,  and with my other smaller panels I do the same except select those of similar Imp to make 36V?

Thanks a lot

[TomW]

Is it if the Imp are very close then I can just put them in series and then parallel them of equal volts. Like 36V made of the recommendations,  and with my other smaller panels I do the same except select those of similar Imp to make 36V?

Thanks a lot

wlyt;

I would agree with that. At 12 volts you probably don't want to go much over 36 volts in from the panels to a Classic. At the worst you might miss a few watts occasionally but it should work well enough. Now, parallel strings can get a bit "interesting" if the cabling and connections are not exactly the same and especially if you have dicey connections.  Your problem is typical of what I think of as "grown in place" systems. You end up with mismatched components. I figure you just put it together the best you can and not get hung up on a perfect match of the panels.Be sure you properly fuse or breaker the system.  Parallel strings would ease any shading issues you could get with longer series strings.

My system is similar with some panels over 20 years old, some 15 and another cluster only 3 years.  Some nominal 12 volt others grid tie type higher voltage units.

It works at pretty well near or above "nameplate" watts on the total of the panels (2.3 KW) into 2 Classics and a Kid so not sure how it will do into one controller but again I wouldn't be too concerned.

Just from here. Your Mileage May vary and  others may not agree.

Tom

[wlyt2000]

Is it if the Imp are very close then I can just put them in series and then parallel them of equal volts. Like 36V made of the recommendations,  and with my other smaller panels I do the same except select those of similar Imp to make 36V?

Thanks a lot

wlyt;

I would agree with that. At 12 volts you probably don't want to go much over 36 volts in from the panels to a Classic. At the worst you might miss a few watts occasionally but it should work well enough. Now, parallel strings can get a bit "interesting" if the cabling and connections are not exactly the same and especially if you have dicey connections.  Your problem is typical of what I think of as "grown in place" systems. You end up with mismatched components. I figure you just put it together the best you can and not get hung up on a perfect match of the panels.Be sure you properly fuse or breaker the system.  Parallel strings would ease any shading issues you could get with longer series strings.

My system is similar with some panels over 20 years old, some 15 and another cluster only 3 years.  Some nominal 12 volt others grid tie type higher voltage units.

It works at pretty well near or above "nameplate" watts on the total of the panels (2.3 KW) into 2 Classics and a Kid so not sure how it will do into one controller but again I wouldn't be too concerned.

Just from here. Your Mileage May vary and  others may not agree.

Tom

Thanks Tom for the valuable advice.

On breakers/fuse, I have not put any yet - and I just learnt very recently that I should. Can you advise me on where/how I should put the breaks?

Like between panels and MPPT charger, or MPPT charger and battery, or MPPT charger and load. As I said, I like Midnite 150 Classic, and I would like to connect my battery (10x100AH SLA of 12V each), load (mainly 12v components) and panels properly.

Thanks in advance!

[vtmaps]

On breakers/fuse, I have not put any yet - and I just learnt very recently that I should. Can you advise me on where/how I should put the breaks?

The most important (essential) place to put breakers is between the battery and everything connected to the battery.

The breaker between the array and the controller is for convenience, not safety.... you use it as a PV input switch for the controller. 

For safety, you also need a breaker on each string of PV panels.  Do your panels have fuse ratings?

--vtMaps

[wlyt2000]

On breakers/fuse, I have not put any yet - and I just learnt very recently that I should. Can you advise me on where/how I should put the breaks?

The most important (essential) place to put breakers is between the battery and everything connected to the battery.

The breaker between the array and the controller is for convenience, not safety.... you use it as a PV input switch for the controller. 

For safety, you also need a breaker on each string of PV panels.  Do your panels have fuse ratings?

--vtMaps

All the specs other than physical dimension of the panels are given in the post above. No special fuse ratings. But the Isc given is described as 'Short circuit current', which is 8.87A for the Mono 150W panel.

So in my case, what kind of breakers of what rating should I use? The battery is suppose to be only connected to the MPPT. So I need one here right?

Total amp rating is then minimal 12 x 8.87 = 106 Amp? Or? My battery if I can, since there are only 10 batteries, I prefer to be using 24V for batteries and 36V for panels.

When you say breakers for each string of panels, what do you mean?

BTW, I managed to climb up my roof and get the specs for the rest of the panels. So all the panels I have are:
1) 6 panels of 150W @ 12V Poly type. Specs is Pmax=150W, Vmp=18v, Voc=22.3V, Imp=8.43A, Isc=8.97A, Max System voltage V=1000VD, Fuse=10A
2) 4 panels of 150W @ 12V Mono type. Spec is Pmax=150W, Imp=8.22A, Vmp=18.25V, Isc=8.87A, Voc=22.45V. Max system voltage is 1000VDC.
3) 3 panels of 100W @ 12v Poly type. Spec is Pmax=100W, Imp=5.59A, Vmp=17.9V, Isc=6.19A, Voc=22.41V.
4) 4 panels of 100W @ 12v Poly type. Spec is Pmax=100W, Imp=5.55A, Vmp=18V, Isc=6.11A, Voc=21.6V.
5) 1 panel of 140W @ 12v Mono type. Spec is Pmax=140W, Imp=7.77A, Vmp=18V, Isc=8.55A, Voc=21.6V.
6) 1 panel of 140W @ 12v Poly type. Spec is Pmax=140W, Imp=7.77A, Vmp=18V, Isc=8.55A, Voc=21.6V. (label scrapped off, should be similar to item 5)

So in the end, I am thinking of 36V system of panels, 4 sets of 150W panels in series for 36V, and 2 sets of  100W panels in series for 36V. Then this 3 sets all in parallel to feed the Midnite classic 150.

Remainder of 1 of 100W and 2 of 140W - I will use in parallel for grid tie.

Any comments?




THANKS.