New solar panels

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Re: New solar panels

Postby APR » Sun Jan 08, 2017 8:56 am

crazyk wrote:A single one of my batteries has a max charging current of 25A.
If I decide one day to expand my array and the PV panels are putting out 33A what happens to the excess current?

I assume this controller will limit the charge current to the correct rate?


You are correct.... The controller can be programmed to limit the current going to the batteries. See the manual for the charge controller....
https://www.victronenergy.com/live/ve.direct:mpptprefs

The software to programme the controller.... you need the proper cable between a computer and controller...
https://www.victronenergy.com/upload/so ... _v1.15.zip
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Re: New solar panels

Postby Gordon-Loomberah » Sun Jan 08, 2017 9:51 am

You could just arrange your panels so that you dont exceed 25A charging, removing the solar noon peak caused by facing them all north, like this: solar-wind-gear/topic5064.html

That charger could then take 4 strings of 2 of your 300W (not 219W) panels, by facing 2 strings west and 2 strings east, ensuring the angle between the orientations is sufficient to limit max charging power to 25A.
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Re: New solar panels

Postby crazyk » Sun Jan 08, 2017 12:25 pm

APR wrote:
crazyk wrote:A single one of my batteries has a max charging current of 25A.
If I decide one day to expand my array and the PV panels are putting out 33A what happens to the excess current?

I assume this controller will limit the charge current to the correct rate?


You are correct.... The controller can be programmed to limit the current going to the batteries. See the manual for the charge controller....
https://www.victronenergy.com/live/ve.direct:mpptprefs

The software to programme the controller.... you need the proper cable between a computer and controller...
https://www.victronenergy.com/upload/so ... _v1.15.zip



Thanks APR, i'll need to read through that documentation. I had read that you need to properly set up the controller for the batteries that are used.

With respect to controlling the charging current with the aspec of the panels, that's an interesting one. Unfortunately I only have a North facing roof to put them on because of other roof penetrations etc so will need to rely on the controller settings.
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Re: New solar panels

Postby crazyk » Sun Jan 15, 2017 10:32 pm

So I have my Victron 150/35 on it's way to me. Should get it in the next few days so I've started to finalise the finer details of my system.

Question 1: is the Ve.Direct bluetooth smart dongle better than the cable? Some of the benefits are that I can program it straight from my phone or ipad.

So my system is going to look something like this and I need help choosing the Breaker sizes, or if I should do Isolators with fuses. Can someone please advise where I should be putting fuses in this setup?

PV panels --> DC Breaker #1 --> Charge Controller --> DC Breaker #2 --> Battery Bank --> DC Breaker #3 --> Inverter

System Summary (I've posted in my previous post)

Panels: 2 x 300W (Suntech STP300-24/Ve)
Voltage Voc: 44.5 x 2 x 1.25 = 112V
Current Isc: 8.83 x 1.56 = 13.3A

DC Breaker #1 = ???

Charge Controller: Victron 48V 150/35 MPPT

DC Breaker #2: ???

Battery Bank: 48V Bank (4x 12V 100ah Narada AG12v100f)
Max charge rate: 25A per battery

DC Breaker #3: ???

Inverter: 1000W Pure Sine Wave (meanwell TS-1000-248C)
DC Input current: 25A Typ


Thanks
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Re: New solar panels

Postby davidg » Sun Jan 15, 2017 11:54 pm

crazyk wrote:PV panels --> DC Breaker #1 --> Charge Controller --> DC Breaker #2 --> Battery Bank --> DC Breaker #3 --> Inverter


DC Breaker #1 = ??? Panels: 2 x 300W= Current limited source, less than 3 parallel strings, only at most needs "DC isolator" not does not need a circuit breaker can use the same DC isolators that are used for grid connected systems.

DC Breaker #2: ??? Charge Controller: Victron 48V 150/35 MPPT = 50A

ABB STD AC Miniature DIN Rail "C curve" circuit breakers are rated for up to 60VDC a double pole version will suit, other brands may also be suitable but MUST have a DC rating.

DC Breaker #3: ??? Inverter: 1000W Pure Sine Wave = 50A as per charge controller.

Allows some head room, so they will not pop unless there is a real issue, should be easy to get from an electrical wholesaler such as "Middys".

Use at least 16mm2 wire or assuming it will fit 25mm2 is better from the controller to the batteries and the same from the batteries to the inverter, keep these runs as short as possible to minimise losses.

Use at least 25mm2 for the battery interlinks again heavier is better, ie 50mm2 or 70mm2 would be better, ensure you use an electrical contact improver grease on all interlink and battery terminal connections.
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Re: New solar panels

Postby crazyk » Mon Jan 16, 2017 9:54 am

Thanks @davidg I'll look into the available isolators and breakers.

If I go with the isolators, I only need to put a fuse on the +ve coming from the PV panels correct?

With respect to the cable sizes, the charge controller can cope with 32mm2 apparently...well that's from the spec.

The batteries have their own interlink bars, I was just planning on using them where possible and then using flex cable where necessary from the charge controller and then to the inverter.

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Re: New solar panels

Postby davidg » Mon Jan 16, 2017 10:03 pm

crazyk wrote:If I go with the isolators, I only need to put a fuse on the +ve coming from the PV panels correct?

The DC isolators used for grid connect systems, which is what I'm suggesting you use are rated for much higher voltage than you will use and are at least double pole which i suggest you use. There weatherproof if used correctly, they turn on and off using high speed spring loaded switching are quite cheap compared to most ELV sub std switching, I see around the place. You will not need fusing in the PV panel cables at all.

A solar panel is current limited source of power a suitably rated fuse will not fail it will never exceed the current rating of it. Theres no point in installing a fuse at all. Fuses only become relevent when there are at least three strings of solar panels in parallel or more. For one or two strings of solar panels, fuses are not useful.
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Re: New solar panels

Postby crazyk » Tue Jan 17, 2017 3:24 pm

Cheers, thanks for that. Yes i'm never planning on expanding this system extensively.

Appreciate the guidance.
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Re: New solar panels

Postby crazyk » Fri Jan 20, 2017 10:31 pm

So I was chatting with an electrician I was introduced to regarding my project and he advised that for Breaker # 2 I could've away with a 25A C curve breaker instead of the 50 noted above.

If could buy the 25A breaker and the MPPT controller is set to max charge current 25A, why would I get the 50 mentioned above?

Also is the voltage of the isolator & breaker critical?
The isolator for instance is 20A 1000v but I'm only going to have 113 V. Does this matter?

Similarly with the breakers. I can get the current I want but the voltages are massive.
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Re: New solar panels

Postby davidg » Fri Jan 20, 2017 11:33 pm

crazyk wrote:So I was chatting with an electrician I was introduced to regarding my project and he advised that for Breaker # 2 I could've away with a 25A C curve breaker instead of the 50 noted above.

I wonder how much DC, batteries and off-grid he does? There's little or no cost difference, the reason why I suggested 50A is you want it to only operate if there is a real issue not trip simply because it was "hot" I've seen this happen quite a lot.

crazyk wrote:If could buy the 25A breaker ............. why would I get the 50 mentioned above?

See above about cost & you can't assume it will only ever output 25A.

crazyk wrote:Also is the voltage of the isolator & breaker critical?
The isolator for instance is 20A 1000v but I'm only going to have 113 V. Does this matter?

No.

crazyk wrote:Similarly with the breakers. I can get the current I want but the voltages are massive.

Your dealing with DC it behaves totally different to AC. As I stated ABB CB's are ONLY rated to 60VDC the ACV rating is not relevant for your use. DCV is what we you are working with here, ignore any rating stated in ACV it's totally irrelevant.

The issue with DC is arcing unlike AC where for 50hz it crosses a zero volts point 100 times per second DC on the other hand is simply on all the time, period.
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PVOutput Stats

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