cant use a transformer on it, I think US Solar batteries do a 6v 240ah, Sonic do 250ah  12v Ritek do the 260ah - the sonic and Ritar are valve regulated AGM with gel technology sealed units, the US Solar are lead acid that you must maintain.... i would go for 2 banks of SOnic or Ritek's 4 x 12v in parallel then into series- keep your cables all the same length and do not use less than 35mm cable with a 100 or 120 amp dc disconnect.  

10 hours ago, Neb said:

Shot again. Ok so in parallel the voltage stays the same and Ah multiplies? In series voltage multiplies but Ah stays the same.

In series voltage adds up and Ah stays the same

In parallel voltage stays the same and Ah adds up

You need 4 x 12v batts for 1  48v bank and another 4 to be able to run them in parallel

12V 260Ah is largest I've seen.

Transformers are for AC. There are things called Boost Converters that can step voltage up, but all they really do is make AC from your DC and then use an inductor to do the step-up, so tech wise it's not that different from a transformer... and basically... just don't go there :-)

For your use case, I'd go with 8 batteries, 2 strings of 4 x 12V in series. That should give you 2 48V strings of 260Ah each. When you put those in parallel, you have 48V and 520Ah.

There are other ways to do this. Example You can use 16 x Trojan T105RE, two strings of 8 in series (8 * 6 = 48V). Then each string is 48V at 225Ah, and the total is 48V at 450Ah.

It is still better if you can rather find larger Ah units and have less strings, but you'd have to look at 6V cells (You get up to 400Ah-ish in 6V format), 4V, or right down to individual 2V cells (that will take you well over 1000Ah, which is too big for your charging capabilities).

The Penny is dropping, Literally and figuratively

[emoji106]

Apparently the lower voltage batteries have thicker plates and actually last longer

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It's simpler than that really. You need a certain amount of lead for a certain capacity. At some point you just have too much of it to reasonably fit 12 cells together. And that's that. Of course, once you decide to package less cells into a unit it does allow using thicker plates... but that doesn't necessarily follow just because it's lower voltage.

You should check out a forklift battery.

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http://ironedison.com/nickel-iron-ni-fe-battery

This looks like good stuff, super expensive.

Anything like this available in SA?

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8 hours ago, Neb said:

http://ironedison.com/nickel-iron-ni-fe-battery

This looks like good stuff, super expensive.

Anything like this available in SA?

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That is what SolarWind uses and apparently it is in a different class. He mentioned something about a local agent. PM him for more details

What about this?

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Cost?

 

Apparently blue Nova is in technopark in Stellenbosch, is just on the other side of this vineyard from where I'm sitting... :-P

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Planning a bank robbery?[emoji848]

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Just my 2c. Your solar array is too big for your needs + battery bank. Perhaps sell some of the PV's and buy extra batteries / the right battery bank for your needs? Will you really consume 9Kw energy for 5 hours every day? Without decent storage for when it's needed, the PV array is overkill IMO. The money could be spent more wisely elsewhere 

The thinking is that with this much PV power, the orientation to the sun and overcast weather should still allow good power generation

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So what I mean to say is that the orientation is not as important as it would be if you were setting up a solar farm and short overcast days shouldn't be a problem. Please Correct me if I'm wrong, I definitely don't need 9 KW but in the middle of winter I will still need 5 or so, not 100% sure

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Neb, let me put it like this. 

Your 30 x 310w panels, 9418kw with losses taken into account, at peak performance in the annual average for SA of 5.5 hours per day, will provide you with 51 797kWh PER DAY (good days)

You have 48v 100ah bank. With 1 day reserve, 50% DOD, you can power about 170w for 12 hours at night. 

That is a bit of a waste as was mentioned before.

What CAN you power with 30 x 310w panels?

You can run for 12 hours at night, 1640w of appliances, with a 48v 965ah battery bank, which, if you use the least amount of batteries, will cost you about R160 000 for 8 x Trojan IND17 6v 925ah batteries - close enough - 1 day spare and not below 50% DOD.

 

So I think the issue came in when you said " My worst case of usage recorded was 40KWh per day ... ". 40KWh is over a 24hour period(?) so whomever worked out the panels, did not consider that you need more batteries for you only have 5.5 hours peak sunlight with +-10-12 hours of no sunlight.

If I was you, I would reduce the load to 15-25KWh, will cost a pretty penny, then put up panels for that and less batteries to be off grid ... and sell the remaining panels to a TTT here at Power Forum at a very special discounted low once in a lifetime offer one cannot refuse kinda deal. 

Does THAT make more sense now ... the numbers, not the good deal?

Hahaha. Like the bit at the end there [emoji3]

Yes you are correct, I'm not using the 100ah batteries anymore.

That was a misunderstanding about grid tie etc and yes, there was a mistake made about the batteries needed (not my mistake, but it's been sorted)

That's one of the reasons I joined this forum, and you guys have helped me understand this stuff quickly(still lots to learn yes!)

I'm busy finding out about a Blue Nova 52v 9Kw battery system, (LiFePo4) I may get that rather.

Not sure why they don't spec the batteries in a standard way.

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16 minutes ago, Neb said:

Not sure why they don't spec the batteries in a standard way.

To confuse everyone ... luckily there are maths to make sure we get the right stuff. 

10 hours ago, Neb said:

Not sure why they don't spec the batteries in a standard way.

Because it is LiFePo4 - they always spec them different to lead-acid. 

You can sell those extra 6 panels to me - Is R1000 per panel a fair price - Just kidding.
I started reading this thread and have felt envious from the start... That much power, I could probably supply my whole street/suburb...

On the serious side though:

• When you going this large, then do it right to start with, mistakes get expensive, and more so at this size.
• At this size, you either are someone who want's to walk away and let it do it's job, or you have an avid interest in getting your monies worth, and getting your money back, I hope it is the latter, because you would make a valuable contribution to the forum with your results.
• It is a bit of a learning curve, which very few "face-to-face" people can help you with, you are going to have to do a bit of homework on many things (it is rewarding in the end)
• Batteries - Seriously, the hardest and most expensive lesson I learned, if you intend on staying on the better side of your supply, your batteries have to be tough and capable. As mentioned above, you can't abuse them, good batteries treated well can exceed even their spec, and more importantly get you better value. As a rough example (battery dependent) - A 80% DoD vs 50% Dod can increase the Battery lifespan/cycles fourfold, nearly eightfold if you go to 30% vs 70%. IMHO, batteries are almost the key to your whole system and it's economy, and they must be looked after correctly. Every type of battery has different requirements, and if you have the dosh, then go for FeO with the right equipment (yeah, that is probably out of everyones price bracket, but they do last 85 +years, and have a DoD of nearly 100%). Realistically, get the best you can afford, but make sure your charger/invertor can support them correctly. Aside: LiFePo batteries are probably reasonable realistic option, but that is according to finances.
• Invertors/Chargers (Separate or Combined) - Despite what is touted by the MPPT Invertor (even me) crowd (sorry JDP and Others), at this size the better move is to do as TTT says and balance everything properly and use high-end parts to do the job intended... But then it HAS to be managed (the system cannot just be left alone, it has to be maintained and monitored). Your best value for money will come from that solution, but how much is your time worth?
• You have spent a fortune (well at least by most of our standards) on this kit - Even if you think you have the right installer, GET A SECOND OPINION, or even a third. Seriously, what is a few hours of labour/consultancy cost vs the value of this investment if it goes wrong? Make sure it is done right - Even knowledgeable people have messed up a Solar install at least once (and I count myself as at least one of those!).

Good Luck, and we would love to see pics of the final install.

Regards

FeO Batteries - I think I might have been dreaming of a perfect world, when I said that! Sheesh, who can afford R25k per 2V ex Import Cost... And thats just for 50Ah! Money no object, even a billionare would balk at that price!

3 hours ago, KLEVA said:

But then it HAS to be managed (the system cannot just be left alone, it has to be maintained and monitored). Your best value for money will come from that solution, but how much is your time worth?

Close, but no whiskey ...

Been running my system since 2012 and all I do every few weeks is to check the water levels of the batteries, measure the gravity and every 3-6 months I swap the outside ones inside and the inside ones outside, then I check all the nuts and bolts and other connections for perfection. That is it!

O, and when I see the panels not being up to standard, they get washed. And for that I have an idea to connect a hosepipe up there, with jets of some sort, to blast the panels clean by connecting the hose and opening a tap, collecting the water in the down pipe to water the plants. Just wondering what will last in the sun. Anyone with an idea?

And one day I will get a 702 and balancers to stop the swapping.

Ps. Anyone who uses batteries have to check them regularly. 

So, inverters work 24/7/365, controllers do their thing and the BMV ensures that the batteries are never drained past my set SOC by switching the system back to Eskom.

Only trick is if I am not home and Eskom goes off ... naaa ... then the load is very little then so the batts will last easily the night and the next day. 

And as per the Pi thread ... reading my data is complicated at best by me having all sorts of different equipment ... after many many years that is also coming very close to being sorted. 

So my point, as you said, with the right equipment, there is not a lot to check or maintain. Having the ability to remotely monitor the system, be warned of problems remotely, that is just the next level up that one can put up your feet and have a beer.

Howzit Kleva.

Thanks for your message.

I've mentioned why I've gone for such a big system before in the thread, so this is about how I managed to get it.

I'm at the start of a big renovation on my house in Tokai, plans have been drawn up with new boundary walls and everything, the existing walls are predominantly vibacrete.

When I looked at the cost of proper new brick boundary walls, I decided to rather fix the vibacrete and spend the saving on a substantial PV system, it's a much better investment.

My brother is an electrical contractor and I've done my fair share of time on site doing electrical installations (my battery calculation skills will tell you otherwise haha)

My boet is giving me a good deal here, don't wanna say too much but I got the stuff at a good price, I still need batteries, the 4 Trojans were returned.

My brother and I are very interested in PV systems, I thought this would be a cool project for us, but not a project that can be screwed up due to poor understanding but also a project that we and others can learn from.

So it was a channeling of funds from one part of the project to another and that's how I justify it.

I am so excited about this system, looking forward to sharing result for sure, I also think this system will pay for its self, it's quite a complex calculation for me because of projected Eskom price increase, inflation, etc etc.

Those batteries are from another planet for sure, 85+ years!!!!! That's madness, that's the one we need. But of course it costs 85 years worth of power.......nothing for free[emoji52]

I like the blue nova system. It's LiFePo4 and it has its own control system and monitoring etc, it's not very sensitive to temperature and it has a reasonable warranty.

I would really love to monitor this system with all the software and a laptop and then generate some useful data but I would need help with that.

Who's in CT that would like to possibly do some consulting work on this system?, my Bro is going to do an amazing installation, I will mention to him that we should get some expert eyes on the system before we actually switch on, sounds like a good idea, better than fireworks in the DB room. [emoji15]

oh ja, I do have time to keep a good beady eye on that system. Also cool that the kids grow up with a solar system I think.

Here's an idea of what the house will look like (not exactly but the shape is correct)

Hey TTT

I reckon you should try copper pipe, thin size and cut a fine slots along the length, almost like perforations.

Dankie ouens

Ben

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2 hours ago, Neb said:

I reckon you should try copper pipe, thin size and cut a fine slots along the length, almost like perforations.

YES!!! That is a brilliant idea!!! Dankie Ben.

2 hours ago, Neb said:

I would really love to monitor this system with all the software and a laptop and then generate some useful data but I would need help with that.

Would like to look at doing this for you.

Ok

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