Solar Regulator advice

[sebrof]

Can you back up that assertion please?

 

I have been in correspondence with the designer of the controller I linked to. He had originally intended to produce an MPPT controller, but decided that it was impossible to do so cost-effectively. This is why the good ones are so very expensive - and not cost-effective.

 

His website makes interesting reading.

 

 

What 1800 Amp hours equals in generater or engine running hours i don't know...all i know is in the summer it keeps up with my energy demands. In the winter it doesn't and i run the engine or generater.

 

It really just sits there doing it's bit...I ignore it most of the time, but i do get a sense of satisfaction when those Amps roll in on a nice day and my energy needs are supplied, something for nothing as I like to ignore the inital cost!!! It works for me, it may not be the perfect set-up, i don't have an MPPT, i don't tilt my panels, i could probably get a few amps here and there if i did, frankly i just want to forget them and enjoy my boat...you can worry too much about these things...

 

 

I think this is the point about solar. It's silent, effective, reliable, hands-off, and has no ongoing costs. Only one of those applies to generators.

[Paringa]

And for those that care at the end of today it is reading 1900 Amp hours...

[canalowl]

Hope this helps...

 

 

I have 4 x 90 watt panels with a Morningstar PWM Sunsaver duo controller. The system has been in for four years now and given me no problems at all; it just sits there doing its thing.

 

I would echo Paringa in that the panels often produce more in the summer than the batteries can take (two Trojan 6v 420 Ah) and a lot less in the winter. In terms of economics even in the summer I have to run the generator for several hours on Saturdays (washing, ironing, hoovering - I only have a 1100 VA rated inverter), and in the winter once or twice in the week also.

 

For me, apart from the joy of harvesting the suns bounty I love being able to drop in the pub on the way home without worrying about being late for the dreaded generator curfew. If I ever bought another nb then fitting solar panels (this time with an MPPT controller) would be the first I would do.

 

Dave

[WotEver]

I have been in correspondence with the designer of the controller I linked to. He had originally intended to produce an MPPT controller, but decided that it was impossible to do so cost-effectively. This is why the good ones are so very expensive - and not cost-effective.

That depends. That's one man's opinion.

 

You can expect something in the region of a 25% increase in output on average across the year with an MPPT controller. If you already have 270W of panels, then you should average in excess of 50W extra power from those panels for less than the cost of a 50W panel. Coupled with the fact that the wiring is dead simple, I think that's highly cost-effective.

 

It's especially relevant if you're struggling for space on the roof.

 

Tony

[Nickhlx]

Last year (September 30th) we had fitted the "max that would fit on the available roof space" solar photovoltaic to take best advantage of the first bracket of the Feed In Tariff. This turned out to be a nominal 3.92 kW peak array (3.99kW is the first "limit"). I have kept daily records of solar generation and some of the findings might be of interest to others. The panels are fixed at the roof angle of about 35 degrees, and "face" about 5 degrees west of South, so not far off optimum for a fixed array. The inverter is a Sunny Boy 3800 which is a "nominal" 3800 watt item and apparently has "MPPT within" - The 16 x 245 watt panels are arranged in two "strings" of 8 panels in series, and the open circuit voltage was shown as around 285 volts from each string. We also have a remote wireless desktop which gives a readout of instantaneous production, production for the day and units produced for the previous 31 days as a bar graph.

 

It has now been working for the 7 full calender months and these first few days in May - total production to date is a very pleasing 1489 kWh, and since about February between around 09-00 and 17-00 our normal electricity meter "stops" as the panels are providing the household draw - At the moment ( 09-00 ) there is already over 1500 watts being produced and our normal "quiescent" consumption is around 400 watts. Daily production is now up to mid 20s kWh and I am hoping for a peak of nearly 30 kWh. The forecast for the returns is slightly lower than we have been getting in practice, probably because the last month has been unusually sunny, but we are well on the way for the annual expected production of 3300 kWh -so, nearly halfway there and still have the main summer months to go.

 

The current FIT rate is now 46.3p/kWh total (increased in April) . The daily consumption from the grid is now down to 6 kWh / day ( for "nightime" usage) from the "before figure" of around 20 kWh/day. Peaks have been seen at around 3800 watts, and, surprisingly, this was not recently, and on hazy days. At the moment, on clear non-hazy days, it is peaking at about 3300 watts, at about 13-15hrs clock time. Production starts at about 06-00 and ends at about 19-30.

 

Naturally, there is a way to go to break even, but I am optimistic it will be within the forecast period and the benefit can only increase as electricity prices drift up. So far I would certainly make the same decision to install

 

Nick

Edited May 6, 2011 by Nickhlx

[sebrof]

That depends. That's one man's opinion.

 

You can expect something in the region of a 25% increase in output on average across the year with an MPPT controller. If you already have 270W of panels, then you should average in excess of 50W extra power from those panels for less than the cost of a 50W panel. Coupled with the fact that the wiring is dead simple, I think that's highly cost-effective.

 

It's especially relevant if you're struggling for space on the roof.

 

Tony

 

From my researches, I very much doubt that you would in reality see a gain of anything like 25% overall, especially with the cheaper MPPT controllers. And the better ones will cost much more than a 50W panel.

 

BTW, I have some great snake oil here that I think you might be interested in.

[Justme]

 

You can expect something in the region of a 25% increase in output on average across the year with an MPPT controller. If you already have 270W of panels, then you should average in excess of 50W extra power from those panels for less than the cost of a 50W panel.

 

 

Sort off.

 

What you will actually get with a MPPT is the full performance of a 270w array compared to a lesser performance using a PWM controller. You wont get the performance of the 270w array PLUS the 25% gains making a 320w array.

(It will perform like a 320w array does with a PWM controller).

[Proper Job]

From my researches, I very much doubt that you would in reality see a gain of anything like 25% overall, especially with the cheaper MPPT controllers. And the better ones will cost much more than a 50W panel.

 

BTW, I have some great snake oil here that I think you might be interested in.

You keep slagging off 'cheap' MPPT controllers and now you intimate that you have 'researched' in to this.

 

I would genuinely be interested in seeing results of data comparing PWM, 'cheap' MPPT and 'better' MPPT controllers.

[sebrof]

You keep slagging off 'cheap' MPPT controllers and now you intimate that you have 'researched' in to this.

 

I would genuinely be interested in seeing results of data comparing PWM, 'cheap' MPPT and 'better' MPPT controllers.

 

If you want to enlist my assistance, try being polite.

[Proper Job]

If you want to enlist my assistance, try being polite.

I had not intended to be impolite.

 

Post #6 you say, "Cheap MPPT controllers don't really work, and those that do are so expensive that it would be more efficacious to buy another panel instead"

 

Post #7 & #9 asks if you can back the statement up.

 

Post #26 you reply, "I have been in correspondence with the designer of the controller I linked to. He had originally intended to produce an MPPT controller, but decided that it was impossible to do so cost-effectively. This is why the good ones are so very expensive - and not cost-effective."

 

Post # 31 you intimate that anyone buying a cheap MPPT controller is wasting his/her money.

 

I am genuinely interested. I have had a cheap MPPT controller for over a year now. It appears to be working. I have nothing to compare it against as I did not have a PWM or any other controller before it.

 

I would just like to know if you (or anyone else) has genuine data that proves they don't work or how there efficiency compares to other controllers.

[Nickhlx]

I would be interested too as I will next year have some funds (hopefully) to put about 100-200 watts on our boat roof and it would be useful to know if the outlay is worth it. I guess one way to test it is to put two similar systems alongside each other and monitor the output over a reasonable time - anyone ?

 

Nick

[WotEver]

Sort off.

 

What you will actually get with a MPPT is the full performance of a 270w array compared to a lesser performance using a PWM controller. You wont get the performance of the 270w array PLUS the 25% gains making a 320w array.

(It will perform like a 320w array does with a PWM controller).

That's understood. The 25% figure I was giving was the increase in performance against using a PWM controller. It was an average of winter improvements (10-15%) and summer improvement (30-35%).

 

Tony

 

... the better ones will cost much more than a 50W panel.

No, they won't. http://www.sunstore.co.uk/buy.aspx?pn=morningstar-sunsaver-mppt-advanced-solar-charge-controller_117506054.htm

 

Tony

[Proper Job]

I would be interested too as I will next year have some funds (hopefully) to put about 100-200 watts on our boat roof and it would be useful to know if the outlay is worth it. I guess one way to test it is to put two similar systems alongside each other and monitor the output over a reasonable time - anyone ?

 

Nick

A while back, I'm sure Gibbo was testing them. I can't find the thread now and I've no idea if he got any results (+ve or -ve)

[sebrof]

Based on my research, which simply means many hours trawling the net, and speaking to people who know more than me, this is my understanding of how solar PV controllers work. Please correct me if I am wrong.

 

What you have to remember about solar panel controllers is that they are a specialised form of battery charger. They are special in the way that they treat low and high voltages, which have to be modified so as to produce a higher voltage under low light conditions, and (in the case of MPPT controllers) a higher current under good sunlight.

 

At the same time they have to work intelligently with the batteries (like any good charger) so that they don't overcharge them.

 

Doing all this well is asking rather a lot, which is why many people are wary of the claims made for cheap MPPT controllers.

 

The unit I linked to does a good job (so the designer says, and he describes how his design does it) of looking after the battery. PWM controllers offer three stage charging, just like good battery chargers. Not being an MPPT design, it does not attempt to increase the current on very sunny days.

 

As I said, where an MPPT design helps is in giving you more current when there is lots of sunshine. It doesn't help on those days when the sun isn't so bright - like the UK in winter (and usually also in spring, autumn and summer)

 

So, a good MPPT controller situated in California or Australia might give 25% better performance than a non-MPPT design, but that doesn't really help us in the UK, where we want to maximise output in winter.

 

I am planning to install an array of panels which will provide more power than I need in summer, whilst making a decent contribution to my needs in winter. In this scenario, which will be the same for any live-aboard in the UK, an MPPT will be much less use than extra panels, and a cheap MPPT might damage my batteries into the bargain.

Edited May 6, 2011 by sebrof

[Gibbo]

A while back, I'm sure Gibbo was testing them. I can't find the thread now and I've no idea if he got any results (+ve or -ve)

 

Yes I started testing a cheapo MPPT controller at my old business premises. Initial results were quite good. It certainly made an improvement over the PWM controller (between 20% and 30% IIRC). Then I sold the company and things all got left. One panel is on the boat with a normal PWM controller (probably switched off). One panel is in the garage (still in the box). The MPPT controller is abandoned in the back of the boat.

 

That's as far as I got.

Edited May 6, 2011 by Gibbo

[sebrof]

I said: From my researches, I very much doubt that you would in reality see a gain of anything like 25% overall, especially with the cheaper MPPT controllers. And the better ones will cost much more than a 50W panel."

 

No, they won't. http://www.sunstore.co.uk/buy.aspx?pn=morningstar-sunsaver-mppt-advanced-solar-charge-controller_117506054.htm

 

Tony

 

Sunstore charger: £224.

50W panel on Ebay: £110. My link

 

I presume a pass in O level maths eluded you.

 

BTW, I would buy a good MPPT controller if I could find one at a reasonable price. The principle is sound; it's the efficacy of cheap ones and the cost-effectiveness of expensive ones that I question.

[WotEver]

Based on my research, which simply means many hours trawling the net, and speaking to people who know more than me, this is my understanding of how solar PV controllers work. Please correct me if I am wrong.

See below:

 

As I said, where an MPPT design helps is in giving you more current when there is lots of sunshine. It doesn't help on those days when the sun isn't so bright - like the UK in winter (and usually also in spring, autumn and summer)

That simply isn't true, sorry.

 

I don't know where you did your research but I'm afraid it's fatally flawed.

 

An MPPT controller allows the panel to operate at its most efficient voltage for the prevailing conditions. It simply isn't true to say that they have no effect other than in bright sunshine. The effect is more marked in bright sunshine, but it's still significant even on overcast days.

 

Tony

 

Sunstore charger: £224.

50W panel on Ebay: £110. My link

 

I presume a pass in O level maths eluded you.

50W panel from selectsolar: £290 my link

 

My maths is quite good thank you

 

Tony

[Timleech]

Yes I started testing a cheapo MPPT controller at my old business premises. Initial results were quite good. It certainly made an improvement over the PWM controller (between 20% and 30% IIRC). Then I sold the company and things all got left. One panel is on the boat with a normal PWM controller (probably switched off). One panel is in the garage (still in the box). The MPPT controller is abandoned in the back of the boat.

 

That's as far as I got.

 

I've bought one of these along with a couple of 50W semi-flexible panels. Gibbo described in another thread how to do a simple basic test to see whether they work (someone had left ebay feedback claiming they didn't), as soon as I get a spare hour or two on a fine day I'll try it, and post the result here.

 

Tim

Edited May 6, 2011 by Timleech

[sebrof]

See below:

 

 

That simply isn't true, sorry.

 

I don't know where you did your research but I'm afraid it's fatally flawed.

 

An MPPT controller allows the panel to operate at its most efficient voltage for the prevailing conditions. It simply isn't true to say that they have no effect other than in bright sunshine. The effect is more marked in bright sunshine, but it's still significant even on overcast days.

 

Tony

 

 

50W panel from selectsolar: £290 my link

 

My maths is quite good thank you

 

Tony

 

Believe what you want to believe old chap.

 

MPPT can't create energy. At lower output levels, it won't send any more energy to the battery than a non-MPPT controller. Both will be flat-out. But it will consume more power when there is no sun.

 

The MPPT controller you linked to is cheaper than an extremely expensive solar panel you linked to. And you think that means you have proved your point.

 

Didn't do so well in logic either, methinks.

[WotEver]

I've bought one of these along with a couple of 50W semi-flexible panels. Gibbo described in another thread how to do a simple basic test to see whether they work (someone had left ebay feedback claiming they didn't), as soon as I get a spare hour or two on a fine day I'll try it, and post the result here.

 

Tim

I'm glad you've bought one of those Tim, I've been hoping someone could give us a review. Of course, one poster here will swear black is white that because it's cheap it's crap

 

Tony

 

MPPT can't create energy.

Correct. I never said it could.

 

At lower output levels, it won't send any more energy to the battery than a non-MPPT controller.

Incorrect. You really don't understand the principle, do you?

 

Both will be flat-out.

Er, controllers don't work 'flat out'. They control the PV panel. An MPPT controller will control the panel more efficiently.

 

... it will consume more power when there is no sun.

No it won't.

 

Tony

[sebrof]

I'm glad you've bought one of those Tim, I've been hoping someone could give us a review. Of course, one poster here will swear black is white that because it's cheap it's crap

 

Tony

 

 

Correct. I never said it could.

 

 

Incorrect. You really don't understand the principle, do you?

 

 

Er, controllers don't work 'flat out'. They control the PV panel. An MPPT controller will control the panel more efficiently.

 

 

No it won't.

 

Tony

 

Yes it will!

 

No it won't.

 

Yes it will!

 

Grow up lad, and produce some facts. I said at the beginning that my understanding might be flawed, and if you think it is, then produce some evidence, not childish nonsense.

 

There is a great deal of contradictory data on the internet, and not a lot of real information. We all have an interest in finding out the real facts, but your contribution has cast no light on the matter at all.

 

Just for once, wouldn't it be nice to have a discussion instead of an argument?

[sebrof]

I've bought one of these along with a couple of 50W semi-flexible panels. Gibbo described in another thread how to do a simple basic test to see whether they work (someone had left ebay feedback claiming they didn't), as soon as I get a spare hour or two on a fine day I'll try it, and post the result here.

 

Tim

 

I note that they claim the improvement will be between 10% and 30%. My expectation is that on average, and especially in winter, it will be rather closer to the former figure than the latter, and at that price I would worry about how kind it would be to my batteries. I wish I could be sure that it had good three stage charging, and was made well enough so that it didn't short-circuit or spontaneously combust.

 

But I would certainly be interested in seeing some results, both with under-charged and fully-charged batteries.

 

Incidentally, I have quite expensive AGM batteries that I hope to keep for many years. I may therefore place a higher premium on battery conservation than some people.

[WotEver]

Grow up lad, and produce some facts

As I recall, the person who started this whole discussion off with unsubstantiated facts that contradict received wisdom on the subject was you, when you made your comment that MPPT controllers are a waste of money and you'll get better results with another panel.

 

I say you're wrong. Support your argument with facts (and I don't mean "I spoke to a guy with a website once") and then we can all learn.

 

Tony

Edited May 6, 2011 by WotEver

[WotEver]

.

Edited May 6, 2011 by WotEver

[Justme]

MPPT controllers dont just increase peak performance. They also allow the bat to start charging much sooner in the day & carry on charging at the end of the day when a PWM would still be doing nothing.

 

A PWM controller will not start to charge a battery bank till the arrays voltage is over the banks voltage. As you are using a PWM controller the arrays voltage will be quite close to the banks voltage (IE a 17-19v array on a 12v bank). So the array needs to be giving quite a bit of its rated performance before it even starts to work & then the same at the end of the day when it will stop charging as the voltage drops off.

 

Now compare that to a MPPT controller with a much higher system voltage (up to 145v in my controllers case) even on a 12v bank. So as soon as the array can hold a voltage under load at over the banks voltage the charging starts. Again at the end of the day it can carry on charging for much longer. Ok the total energy going into the bank is low but by then the bank will nearly be full & only need a small charge to finish off the full 100% charge.

 

My system can start & finish charging the bat at 10% of its working voltage. With a PWM I would be getting no charge at all.

 

Also remember that with the higher array voltage you can run smaller (IE cheaper) cables for the same total power with less losses.

 

 

The issue now is that PV panels have dropped so much in price to nearly £1 per watt it could be cheaper to have a larger array (if you can fit it on your limited boat roof space). When we bought our set up PV panels were nearly £3 per watt so the MPPT controller was more cost effective than adding more PV. I think the cost difference was about £400 between the PWM & the MPPT which would have bought about an extra 140watts. As even an average increase of 12% from the MPPT still made is a better bet.

(just like a bought in tracker can be out performed for the same cash spend by fitting more panels)

Edited May 7, 2011 by Justme