Have bitten the bullet and upgraded to 24v but...

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Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Sun Dec 06, 2015 5:02 pm

I am having a few issues with the upgrade I am performing and hoping to get some direction. 12v was all too easy but got to the point where we had to do something so I have basically done a complete upgrade, I had 800w on each outback but now I want to put 1380w on each one but understand very little of strings, I just made two arrays (3 x panels on each) going into the one set of 6mm cable but think this is not the right way as I am only getting 4 kwh a day input and the max watts I am getting in is around 480w which seems low for having 1380w now on it (was getting more input on 8 x 180w chinese panels and the new ones are german made and meant to be far superior) I have adjusted angles to see if I would get more but I am getting at most 21 amps going in, this doesn't seem right so I have come to all things outback to get the sound advice and right way of doing it. Thanks in advance for any help.
Last edited by Halal Bacon on Mon Dec 07, 2015 1:28 pm, edited 1 time in total.
Halal Bacon
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My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
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Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Sun Dec 06, 2015 5:44 pm

I forgot to mention that I have gone parallel, I am getting 26v in at the outback, is this not enough? I know series adds voltage and parallel adds current but should I be adding in series? I struggle to understand this side of the install.
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My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby SandyP on Sun Dec 06, 2015 11:07 pm

Halal Bacon wrote:I am getting 26v in at the outback, is this not enough?


Nope, not high enough for proper (or any reasonable) charging of your FLA batteries - you need to (quickly) restring your solar panels.
For the MPPT charge controller to work best you will likely need >35V into the CC, therefore two panels in series will give the required voltage.
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Mon Dec 07, 2015 12:05 am

Thanks Sandy, I was thinking that might be the problem, what I don't get is why? If parallel adds current then why the advantage of going in series?
Halal Bacon
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Posts: 9
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My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby SandyP on Mon Dec 07, 2015 2:22 am

Halal Bacon wrote:If parallel adds current then why the advantage of going in series?


Some advantages are :

1) Higher voltages mean less power loss on the lines from the solar panels to the charge controller.
2) Able to use solar panels with voltages that may not suit the batteries when used with a PWM controller
3) MPPT controller will convert the excess voltage into amps anyway
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Mon Dec 07, 2015 4:47 am

Would two strings of 3 be the go?
Halal Bacon
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Posts: 9
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My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby klundquist on Mon Dec 07, 2015 8:58 am

Probably but to be safe, what is the Voc rating for your PV module? You can find this on a sticker on the back of the module, or on the spec sheet. What is the record low daytime temperature where you live?

-Kurt
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Mon Dec 07, 2015 1:27 pm

Thanks for your input Kurt, temperatures run around 90 this time of year and the Voc is 36.87
Halal Bacon
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Posts: 9
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My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby klundquist on Mon Dec 07, 2015 1:30 pm

If it never gets below freezing I'm confident that two parallel strings of 3 in series is the best setup. This assumes that you do not have any partial shading issues on the array.

-Kurt
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Mon Dec 07, 2015 1:51 pm

Thanks very much for that, can I ask why partial shading is an issue?
Halal Bacon
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Posts: 9
Joined: Fri Dec 04, 2015 7:52 pm
My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby klundquist on Mon Dec 07, 2015 2:26 pm

It takes very little shade to shut down PV production. For example a fist sized amount of shade can reduce PV module production by 75% or more. If the shaded module is wired in series with other modules, the other modules will also reduce their output. Certain PV modules have equipment such as bypass diodes to mitigate the amount of power that is lost from partial shading. For more details here is an article that I found from a quick search online http://www.solarchoice.net.au/blog/partial-shading-is-bad-for-solar-panels-power-systems/

-Kurt
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Mon Dec 07, 2015 2:39 pm

Thanks once again for your valuable input!
Halal Bacon
Member
 
Posts: 9
Joined: Fri Dec 04, 2015 7:52 pm
My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby SandyP on Mon Dec 07, 2015 11:47 pm

Halal Bacon wrote:Would two strings of 3 be the go?


Have a look at the information on the web page below, the Excel spreadsheet calculator may also be of assistance :

http://www.victronenergy.com/blog/2014/ ... egulators/

PS. you will need to edit the solat "Modules" tab sheet of the spreadsheet to enter the info for your own particular panels (enter in the custom 1XYZ 1ABC).

The following technical paper may also help to visualize how the MPPT charge controller can maximize power into your batteries :

http://www.victronenergy.com/upload/doc ... r-MPPT.pdf

Page 8 states :

Conclusion:
When using an MPPT charge controller there are two compelling reasons to increase the PV
voltage (by increasing the number of cells in series):
a) Harvest as much power as possible from the solar array, even at high cell
temperature.
b) Decrease cable cross sectional area and therefore decrease cost.
SandyP
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Joined: Tue Jun 21, 2011 4:44 am
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Outback VFX3024 Inverter/Charger
Victron BMV-602s
Honda 5.5kW Genset

Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Tue Dec 08, 2015 1:50 pm

Thanks for those links Sandy, given me a good insight to the workings of mppt.

Panels are done, was excited to see how it was going to perform but today is a day of cloud and rain so will have to wait, I do see that the outback is working as it should so thank you both for helping me out.
Halal Bacon
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Posts: 9
Joined: Fri Dec 04, 2015 7:52 pm
My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah

Re: Have bitten the bullet and upgraded to 24v but...

Postby Jacotenente on Wed Dec 09, 2015 6:35 am

Best of luck with your system. I think you are on the right track.
FWIW - I started with a 12v system years ago. I paralleled by 12v battery bank and solar panels going into my old 30A MPPT solar charger. Small peanuts for the most part. After upgrading, watching what others did, talking on this forum, Outback Power, Midnite Solar, and experts I learned a few things:

1. With MPPT (Flexmax 80 or Classic 150/200), higher PV array volts work excellent...I get great charging amps. VMAX is about 129 volts...operating at about 107v
2. PV shading is bad, really bad. However, you can do some creative PV panel wiring of your strings. Or separate your strings with multiple chargers.
3. 12v to 24v battery bank (48v is even better) - Higher efficiency going to 24v. I even use 2/0 battery cables on my Trojans...no issues at all
4. Winter (northern hemisphere...ie, Canada, USA, Europe) sucks for daylight/solar power production. At my latitude there is 5 hours less daylight difference between spring and winter solstices (June and Dec). Making power in the winter is reduced. I figure about 30% or so...just my numbers/nothing scientific
5. I still use the grid (for the 240v side, occasional charging, some 120v overnight power use). My house 120VAC circuits are on renewable energy. My last electric bill was $43. I have been collecting Optics RE data since April and the results are eye opening. Anywhere from 35-65% reduction in the electric bill. I have A LOT of room for improvement though.
6. There is a huge community to help you if you reach out.
7. Off-grid set ups (IMO) have a lot of benefits. Grid-tie is also great if you can find a electric company willing to "net-meter". Trend in the US is not looking good for grid-tie...since RE costs are at historic lows.
8. Making solar power is like "magic"...I know, sounds crazy. But, I still get a youthful kick out of making my own power and flipping off my local electric company.

Cheers!
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Re: Have bitten the bullet and upgraded to 24v but...

Postby Halal Bacon on Wed Dec 09, 2015 1:43 pm

Thanks for replying. I now believe we are on the right path, taken two years to get my head around it and still massive amounts of learning to be had but very very happy with how it is all coming along. We have a power pole available out front but it would be 300m from the house and (about $10000 to get it here), truth is we are very frugal with our usage so off grid suits. Our water is gravity fed, lights are all LED, the tv is 12v LED and we have 12/24v fridge and chest freezer. Sat net is a few amps, sat tv a few and composting toilet also a few amps.. Hopefully the ears stop bleeding now (we could of put mains on and paid five yrs worth of power, when can I run this, I need power for that nag nag nag). As they say, happy wife=happy life. Really appreciate everyones input greatly.
Halal Bacon
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Posts: 9
Joined: Fri Dec 04, 2015 7:52 pm
My RE system: 6 x 230w Conergy power plus
4 x 180w Astronergy
2 x outback mx60
Victron 24v/3000va/70a inverter charger
Victron BMV 601
12 x 2v flooded 750ah


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