Designing new 12VDC Off Grid system. Many questions. (Midnite 150)

[Vic]

OK, I've had a bit of a chance to catch up with the reading.

Vic - Those DC breakers look good. And the price is about a third compared to the last time I looked so good one thanks!
I as specially like the ones from the first two links.
Midnite Solar MNEPV 150 VDC 80A and 100A Solar Array Breakers - Will use this for he array breaker (As suggested).
The wiring confuses me though. Looks like both switches are combined to try and share the load or something?
Shouldn't solar panels be totally isolated when switched out?
MNEPV Midnite Solar MNEPV 1 to 63 Amp 150 VDC Breakers for Solar Panel Arrays - And will use some of these for the DC fuse box to break out to different DC outlets in the different rooms.
I notice that you reference http://www.solar-electric.com as the supplier. I have been dealing with http://www.altestore.com previously. Any preferences which might be the better one to go with?

I've also decided to run all the panels in parallel. Cable combiners have become a lot cheaper over time and I prefer to work with lower voltages so I'll be doing it that way which is better anyhow.
I might also only start out with 4x panels (1KWatt) for starters as I'm tempted to play around with the other two using Aurora Micro grid tie inverters at another location for a bit.

Hi Ken,

Thanks for the update.

YES,  the DIN-Rail 80 and 100 Amp breakers use two breakers linked mechanically,  and wired in parallel.  These are most often used on the output of a CC -- the connection to the battery.

Normally one would the single gang MNEPV breaker for the PV input,  as  these single breakers have ratings to 63 Amps,  which is usually fine for the PV input to the CC and they will be completely isolated from the 80 or 100 A breaker.

I do believe that a number of Down-Under folks do use alt-e as well as wind-sun.  It is mostly down to reliability/reputation of the company,   the shipping costs, ,  item price,  customer service,  etc.

Often use wind-sun here, as they have very good pricing,  quick service,  and are reliable.  Have never used Alt-e.   Do also use Colorado Solar (SolarPanelStore),  and they are very good,  but often ship from Distributors,   FWIW.

Fine on running all PVs in parallel,  sounds fine to me,  although,  as your PV array grows,  the cable size will become large,  due to the higher current from the low voltage of single PVs in parallel.

Have Fun,  please keep us posted.  73  GL Vic
_..._._

[vk4akp]

Hi, Only a quick one tonight. Late already and we have a big weekend ahead including a Ham Fest at the coast!

But you've got me thinking again. Making more shopping lists.
I'd really like to see the system installed before 2015 which of course is when the UFO's start landing!

Any idea how to work out the current ratings of the cabling?
I'll be using the industry standard 4mm cable and MC4 connectors as used on the grid connect stuff.
The solar panels are already factory fitted with this so I'll make the rest of the run the same.
So that has me wondering about current ratings?

I ran the Midnite Classic Sizing Tool and it came up with 49.86 Amps @ 30.1 VMP for 6x CSUN-250-60M 's in parallel.
Or 24.93 Amps @ 60.2 VMP for paired series paralleled.

The cable run from the panels will be definitely under 10 Meters, possibly even less then 6 Meters.

Now on another note, when it comes to cabling up the panels even just to get 4x on the roof for starters (paralleled) it looks like I will need 3x pairs of "Y" cable's (6 total) & 4x 1 meter patch cables. (Each Panel is 1 meter wide). See: http://www.csun-solar.com/fileadmin/dateiablage/media/datasheets/m-mod/en/CSUN250-60M_ENG.pdf

From this point the final run of cable from the roof to the panel isolation switch at ground level. (5 - 10 meters).

Brings me to another questions. Does it harm panels leaving them open circuit for long periods of time? IE If I install and wire up to the isolation switch and then leave that disconnected for a time while building the weather proof hut to house the Midnite Classic etc.

Now back on to DC breakers.
I've found these http://www.cnakm.net/125a-DC-Miniature-Circuit-Breaker-MCB-Mini-Circuit-Breaker-p15061227.html

http://img.leadong-web.com/html-en/image/25-vZKfVdcWIDQw-1-1.jpg

AKMAN YJB1Z-125
125Amp DC
1P 220VDC
2P 440VDC

Under AU$20 each delivered.

What do you think? Buy 3? One for panels, one for between the Classic and the battery, & one for the load off the battery?

Oops, brings me to another question! LOL.
Batteries are 2x paralleled 12VDC Panasonic LCXA12100P (100Ah/20h).
http://industrial.panasonic.com/www-data/pdf2/ACD4000/ACD4000CE120.pdf

Whats the maximum current you can pull from these without hurting them?
The spec sheet doesn't really say.
But it's highest current draw info suggests 55Amps for 1 Hour?
So with 2x paralleled I guess a 100Amp breaker is probably enough?

Eventually I plan to go NiFe batteries anyhow. But I have these Lead Acid Panasonic's already and they were only $20 each ex government second hand so worth using to start out with.

OK Sleep time me things!. TNX all!
.-.-.

[Vic]

Hi Ken,

Regarding the cable run from the PVs.  The 4 mm cable that you mentioned,  assume that this is 4 mm Squared in cross sectional area,   or about 9.5 AWG ??  If this is the case,  it is probably too small for the run from your COMBINER box to the power room.

You WILL need a combiner,  with three or more PVs.  This combiner will have one circuit breaker (best) or fuse per each PV to protect against fire hazard from a shorted PV.

Circuit breakers really protect the cable that attaches to them.   So,  you will want a considerably smaller breaker than 125 A.   Your 250 W PVs will hare a Max Fuse size stated on the label on the back of the PV module.  Often it is 15 A.   Hope that you can find the CBI/MidNite breakers at a reasonable price there ...  they are designed for the Solar service,  and fit into the MidNite boxes,  which are also rated for the Solar applications.

That Pana battery appears to be Gel,  and probably really intended for UPSes.  Usually not good to use Gels for cyclic PV applications.  They are very picky on charge voltage and have a limited ability to take high charge currents.  And,  if this is a UPS battery design,  it  will not be very good for very many cycles.  These usually just want to be on Float 24/7,  with an occasional,  short cycle when the AC power goes down.

EDIT:  You may not see this Ken ...   but   forgot to mention that PV modules will not be harmed by mounting them and leaving them disconnected,  or otherwise not delivering power.   There is a very small reduction in the output that is caused by exposure,  and there are slight risks of physical damage that might not happen,  if the PVs were stored in their original packaging,  etc,  but in general,  you should have no worries.

More Later,  Thanks,   73,      Vic

[vk4akp]

Hi Vic,

Thanks for all the good info.

So I can't combine the 4x panels up on the roof under the panels using "Y" cabling?
Is this because the combined current would be too great for any sensible sized cable run?
So for 4x panels I have to run a total of 8x 4mm^2 cables down to a combiner box with individual fuses on each wire (8 fuses) in a combiner box?
Then combine into very thick wire (Like on the starter motor of a car) into a main breaker fuse that should be a bit over the combined max current capacity of the panels?
And the same very thick wire to the "Classic" and to the batteries? (Large breakers in between each? Possibly 100Amp).

Maybe there is a video on this somewhere that I can watch on setting up an array like this?
Shame there are no hobby groups anywhere doing classes etc. Like for making mud brick homes etc.

Batteries were almost a gimmie @ AU$20 each. So I will just run them till they fail and save in the mean time for some NiFe batteries to replace them. Still deciding on a battery supplier from China. There are a few now. Plus it's a big investment. If I go over AU$1G for the purchase I pay import duties as well. So some things to look into yet.

Spec sheet says the panels "Series fuse rating (A)" is 20 Amps.

Panels have been stored in my bedroom about 2-3 Years now. 
They didn't come boxed. Just cardboard on the corners to protect them. I believe they are imported stacked on pallets in bulk.
I stored them back to front on each other to protect the backing (vinyl lining) so two a piece with glass always facing out. 



.-.-.

[vk4akp]

OK. I've just found some training video's on the Midnite site.
I had watched a few before but didn't realise the relation between the "Disco" reference and Array Isolation until you used the term in your message.

I see what's going on now.
I was hoping to just run one pair of cables, but I see now that that's not going to happen.

So a "MNPV4" combiner looks the Go? http://www.midnitesolar.com/productPhoto.php?product_ID=393&productCatName=Combiners%20-%20Pre-Wired&productCat_ID=35&sortOrder=3&act=p

With maybe a lightning surge protector as well.

Do I still run a separate breaker between the "Disco" and the "Classic" or not necessary?
Just between the Classic and the battery and another between the battery and the load.

Is the MNPV4 water proof for outside mounting?

And are the connectors at the bottom MC4?

.-.-.

[vtmaps]

So I can't combine the 4x panels up on the roof under the panels using "Y" cabling?
Is this because the combined current would be too great for any sensible sized cable run?

It's because if one panel shorts out, the combined current from the other three panels could flow (retrograde) through the shorted panel and cause a fire.

Then combine into very thick wire (Like on the starter motor of a car) into a main breaker fuse that should be a bit over the combined max current capacity of the panels?

Depends on the length of the cable... use a voltage drop calculator to determine the gauge of the cable.

Do I still run a separate breaker between the "Disco" and the "Classic" or not necessary?
Just between the Classic and the battery and another between the battery and the load.

Is the MNPV4 water proof for outside mounting?

And are the connectors at the bottom MC4?

The cable between the combiner and the controller is sized large enough that the power source (your array) can never cause overcurrent.  Therefore, for safety no fuse or breaker is needed.  However, a disconnect is required and it must be mounted very near the controller.  A breaker makes a good switch, and is usually used for a disconenct.  Its purpose is to turn on/off the PV input to your controller.  That is something you will need to do from time to time.

All Midnite PV combiners are outdoor rated.

Yes, those connectors on the bottom are MC4.  Be careful ordering the combiner... the usual configuration with MC4 connectors has high voltage fuses, not 150 volt breakers.  Insist that you get one with breakers, not fuses.  btw, you can order them prewired. 

On the subject of prewired... did you know that you can order a Midnite ePanel (as a kit or prewired) with a Midnite charge controller and an inverter.  It includes all breakers, bypass switch, shunt, surge protectors, etc.  Just screw it to the wall, connect the PV input, the battery cables, the AC in and out, and the ground cable. 

--vtMaps

[vk4akp]

Hi, Back again. Still sourcing parts.

OK. I ordered a 2P 100Amp DC breaker and it looks quiet good so I'm about to order some more from the same company.

I was going to get another 2x of the 2P 100Amp + 6x 1P 16Amp DC breakers (For the panels).

I couldn't get 15Amp ones and the Panels are supposed to have 20Amp fuses internally so I am hoping 16Amp is close enough? (still a 4Amp buffer) And I know the current could potentially peak past the 16Amps before the breaker finally throws. Hopefully it will still safeguard the Internal Panel 20Amp Fuses.

The 100Amp 2 pole breakers I will use them as.

1. Panel main disconnect switch. (After the 4-6x 16Amp ones).
2. Charge Controller to battery disconnect switch.
3. Battery to load disconnect.

Does this all sound good enough?

I can also get 125Amp breakers for the main load disconnect switch but I think pulling 100Amps on the main output is enough.
I'm not even sure yet how thick the wire needs to be to support that current at 12VDC. ??

Comments please?
.-.-.

[kf4hzu]

I can also get 125Amp breakers for the main load disconnect switch but I think pulling 100Amps on the main output is enough.
I'm not even sure yet how thick the wire needs to be to support that current at 12VDC. ??

Hello! I am also new to Pv and I found this thread when digging around on the forum for others with 12V systems. I may be able to answer this question for you!

I have a 2000W Samlex pure sine-wave inverter connected to my 12V battery bank for intermittent use. According to the manual it needs 1/0 AWG wire (8.25mm aka 53.48mm2) to have sustained 200A draw from the batteries. I never run it above 150A so the 1/0 AWG wire I have works just fine with 250A in-line fuses for safety. Also note my cable run is less than 3 feet, which matters a lot.

For 100A from 12VDC, depending how long your cables are, I would suggest 4 AWG (5.19mm aka 21.15mm2) minimum. This would give you about a 2% voltage drop across 5 feet. I try to design all of my stuff for 1% or less loss where possible, but I also have a very small footprint that everything fits in so my cables can be very short. If you can afford it, buy 1/0 AWG. I'm still learning the Pv side of things, and proper battery bank design/management. But one thing I knew going in to this was reducing voltage drop on a 12V system is critical.

This link may come in handy when sizing cables:
http://www.rapidtables.com/calc/wire/voltage-drop-calculator.htm

Just remember to change current type to DC

Hope this helps! The M4-ATX 12V PSU is very cool. I may even build a small server box to run off my system as it grows now that I know 12V PSUs exist. I have seen 48V ones in datacenters but never 12V. A lot of what you have been trying to do on this thread is what I am also trying to do since I want to stay with a 12V battery system. Looking forward to reading more about your system!