Good article on Solar Panels in issue 238

Treecrest14 · Senior Member

Good article on Solar Panels in issue 238

PeterD · Guru

Is this the one you mean? When you are reading an article there is an address to it up the top of the browser. Why not post that link?

T1 Terry · Guru

From the article:
While PWM is a mature, low-cost and reliable technology, a MPPT regulator is far more efficient. In fact, a MPPT regulator can extract as much as 30% more energy from a solar panel than a PWM regulator can under the same solar conditions. The reason a MPPT regulator is so efficient is that it constantly checks where the maximum power point of the connected panels is and adjusts its input impedance to keep the panels at this point.

Why do people just quote the nonsense in the sales brochure, 30% more is simply nonsense unless the panel is mismatched to the system, like a 24v panel for a 12v battery, the example panel used in the article was 18v @ 25*C. We all know that the panel will not remain at 25*C when it's exposed to full sun light for any period of time but simply saying the power derates is not a good explanation of what really happens. The explanation that power is volts x amps is correct, but the amps reduce a very small amount as the panel increases temperature, it is the max voltage that those amps can be generated is the part that reduces, so the quoted 5.56 amps x 18v = 100.08w, but when the panel gets hot that voltage drops to around 15v, now the equation is 5.56 amps x 15v = 83.4watts. There no magic inside an MPPT controller that can get anything more out of that panel at the real Aust operating temp. In fact the MPPT controller requires some of that solar power to run, so not much hope of getting more out of an MPPT controller than you can get out of a PWM controller if the panel voltage range is matched to the battery voltage in Australian conditions I'm afraid.
All the test results are based on very cold climates where the panel temp will remain below 25*C, can you think of any conditions where you have free camped were the panel or anything else in full sun remained at less than 25*C? Do you really take your van up onto the snow fields biggrin

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T1 Terry

oldtrack123 · Guru

Actually the article is well written & factual biggrin

It does point out the temp/ output loss.

What some do not seem to understand or accept is that the gain depends on the load voltage ,

Lithium batteries with their narrow working range over a range of loads are almost already perfectly load matched to the PPP of hot cells of a nominal 12V battery charging panel

But the situation is a lot different with LA batteries whose load & SOC voltage could regularly be around 12V

That is when full utilization of panel output [what ever it may be] could be required & when the distinct advantages of MPPTs shows

Not sure how using panels in series with a MPPT can be considered a mismatch .

BUT certainly would be stupid & badly mismatched if using a PWM confuse

T1 Terry · Guru

oldtrack123 wrote:
Actually the article is well written ï¿½& factual
It does point out the temp/ output loss.
What some ï¿½do not seem to understand or accept is that the gain depends on the load voltage ,
ï¿½
Lithium batteries with their ï¿½narrow working range ï¿½over a range of loads are almost already perfectly load matched to the PPP of hot cells of a nominal 12V battery charging panelï¿½
But the situation is a lot different with LA batteries whose load ï¿½& SOC voltage ï¿½could regularly be around 12V
ï¿½That is when full utilization of panel output ï¿½[what ever it may be] could be required & when the distinct advantages of MPPTs shows
Not sure how using panels in series with a MPPT can be considered a mismatch .
BUT certainly would be stupid & badly mismatched if using a PWM

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You miss the added inefficiency in the MPPT controller the greater the voltage mismatch is Peter. You also ignore the fact that the greater internal resistance in a lead acid battery means the charging voltage climbs mush faster so that lower voltage at the battery is a very short term thing, it doesn't take long before the voltage is actually higher than the lithium battery so the mismatch is even less, unless you deliberately cause a voltage mis-match just to make the controller work, Irish engineering at its best biggrin

I know it is hard to accept Peter, but the whole theory base used to support MPPT low voltage solar controllers is an incomplete equation, so the theoretical result is incorrect, anyone who has actually done the side by side comparison can verify this. Put all the figures into the equation and MPPT is behind the 8 ball unless the voltage between panel and battery is deliberately mismatch.... why would anyone want to that just to get an expensive controller to appear to be worth the $$?

On a house system the cable length is enough to possibly justify the reduced cabling cost by using smaller conductor cables to equal out the extra cost of the controller. Please don't try to do the comparison with the cheaper rubbish end of MPPT market, the real deal such as Midnite solar, Outback Solar (genuine not the Chinese knock off that doesn't work anything like the real thing)Â the upper range of the Victron stuff, not the bottom of the range because it is built to a price not a performance level. Morningstar suffer heat derating at 40*C, it doesn't take long for the heatsink under full load and an ambient temp in the 30*C mark to climb above the 40*C mark, they were built for much cooler climates so have no fan to move air across the heat sink, simply not made for Australian conditions. Yes, I have talked with the engineers from Morningstar on aÂ direct link Webinar and they accepted the fact their controllers did not suit such a climate, they didn't realise it got that hot in Australia confuse

Look at the Kyocera chart and it doesn't take long to realise just how much the panel output is effected by heat, that 75*C mark is there for a reason, the manufacturer knows full well the panels can reach such a temperature

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Kyocera 140w panel with single voltage increments.jpg

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T1 Terry

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oldtrack123 · Guru

Yes confuse

Everyone is wasting time & money selling ,buying ,using REAL MPPTS in Aus ,because ALL the panels all over Aus are always operating @ 70C & everyone operates their battery around 14V ,even under load

It also seems that we are being told, that immediately one connects a charging source to LA batteries in a low state off charge , the voltage suddenly shoot up to around 14V .???

That would only occur with very high charging currents,& if true most chargers would quickly go into float mode!![due to how you interpret the effects of battery internal resistance

I am sure most members would know THAT does not occur smile

Talk about selective cherry picking to try to justify an "opinion" or limited experimenting

It is a long accepted fact that if you set out to prove a point by experimenting ,you can be selective enough to getresults you want.!!

Even selective quoting can do a good job too

I will say no more on the subject & leave other independent members to come to their own conclusions , [but posts from the brainwashed brigade will not mean much]

To those who have & do know the results of using MPPTs, it must just be your imagination that indicates there are gains over time

One way to ensure you keep your panels as cool as possible is to ensure you have a good air gap beneath them for good airflow [do not attach directly to roof]

& helps keep the van cooler [tropical roof]

Not sure what some will do when their beloved PWMs are no longer available[obsolete] biggrin

Of course with voltage matched panels ,one does not need much more than a VSR with a narrow differential /hysteresis for charge control [so simple that virtually anyone with some basic electronics could make one!!!]

ps I have no commercial interest of any sort on THIS or lithium battery related subjects !!! No commercial barrow to push!!

-- Edited by oldtrack123 on Tuesday 11th of October 2016 02:52:38 PM

T1 Terry · Guru

You do make a few very good points Peter, even if you didn't realise you were doing it. How many times have you heard someone say their lead acid batteries were full by 10am or mid day? How was this determined, either because the battery reached 14v or something or because the controller dropped into absorption or float mode..... but was the battery really fully charged? If the battery voltage has reached 14v or more by 10am then what value is the MPPT controller going to contribute to the potential charging current? The panel voltage isn't much higher than the battery voltage so there is little to be gained there and the controller is already limiting current flow anyway to stop voltage run away, so even if the MPPT could extract another 5% it can't be used because the voltage limit has been reached, the 5% plus more is being left on the table because the battery can't accept it without increasing the terminal voltage.

You have to look at the whole picture, not just a snapshot of information, but I think you may have already mentioned that

T1 Terry

mr glassies · Guru

Obliviously that wasn't a moot controls you fitted to my system terry . Because today is awesome 60 amps going in or was that amp hrs or was that watts o I don't know any more but I think they were full at about 10 having used 26% last night .

I didn't know lithium batteries had a narrow working range pleas explaine

Dibs

PeterD · Guru

T1 Terry wrote:
From the article:
While PWM is a mature, low-cost and reliable technology, a MPPT regulator is far more efficient. In fact, a MPPT regulator can extract as much as 30% more energy from a solar panel than a PWM regulator can under the same solar conditions. The reason a MPPT regulator is so efficient is that it constantly checks where the maximum power point of the connected panels is and adjusts its input impedance to keep the panels at this point.

Why do people just quote the nonsense in the sales brochure, 30% more is simply nonsense unless the panel is mismatched to the system, like a 24v panel for a 12v battery, the example panel used in the article was 18v @ 25*C. We all know that the panel will not remain at 25*C when it's exposed to full sun light for any period of time but simply saying the power derates is not a good explanation of what really happens.
All the test results are based on very cold climates where the panel temp will remain below 25*C, can you think of any conditions where you have free camped were the panel or anything else in full sun remained at less than 25*C? Do you really take your van up onto the snow fields

For those who do not take notice of a few who know the implications of choosing the correct style of regulator, look further to a manufacturer of both MPPT and PWM regulators. First go to the Victron Energy page Which solar charge controller: PWM or MPPT? There is a link to a white paper on that page that gives a of the situation.fuller explanation

oldtrack123 · Guru

mr glassies wrote:
Obliviously that wasn't a moot controls you fitted to my system terry . Because today is awesome 60 amps going in or was that amp hrs or was that watts o I don't know any more but I think they were full at about 10 having used 26% last night .

I didn't know lithium batteries had a narrow working range pleas explaine

Dibs

Perhaps YOU missed that is one of T1's main claims for them

How they hold their voltage over such a full range of loads & SOC

Seems YOU did not understand blankstare

oldtrack123 · Guru

T1 Terry wrote:
You do make a few very good points Peter, even if you didn't realise you were doing it. How many times have you heard someone say their lead acid batteries were full by 10am or mid day? How was this determined, either because the battery reached 14v or something or because the controller dropped into absorption or float mode..... but was the battery really fully charged? If the battery voltage has reached 14v or more by 10am then what value is the MPPT controller going to contribute to the potential charging current? The panel voltage isn't much higher than the battery voltage so there is little to be gained there and the controller is already limiting current flow anyway to stop voltage run away, so even if the MPPT could extract another 5% it can't be used because the voltage limit has been reached, the 5% plus more is being left on the table because the battery can't accept it without increasing the terminal voltage.

You have to look at the whole picture, not just a snapshot of information, but I think you may have already mentioned that

T1 Terry

Another long post picking particular conditions to suit the argument for PWMS

Yes ,IF you have large solar input compared to capacity used or battery bank capacity ,you may well get that situation of over voltage ,not true SOC, due to battery internal resistance .Nothing startling new about that particularly with LAs

Just another case of picking an unusual situation to try to justify the PWMs

BUT strangely "???"PWMs will see those batteries as fully charged also biggrin ,so what is the point ?????

YES , one does have to look at the whole picture , that means comparisons over a large range of identical conditions./[batteries panels weather etc] not just a few picked conditions that suit the required outcome

So many variable that few amatuer experimenters could ever hope to produce meaningful results .

Thanks Dibs, there has been some reluctance to post that sort of information ,so others could understand how so much can be run from lithiums biggrin

Good to see you had the room to fit over a 1000W of panels,probably more like 1500W! since they would be flat mounted ,& you are only using PWMs biggrin

T1 Terry · Guru

oldtrack123 wrote:
T1 Terry wrote:
You do make a few very good points Peter, even if you didn't realise you were doing it. How many times have you heard someone say their lead acid batteries were full by 10am or mid day? How was this determined, either because the battery reached 14v or something or because the controller dropped into absorption or float mode..... but was the battery really fully charged? If the battery voltage has reached 14v or more by 10am then what value is the MPPT controller going to contribute to the potential charging current? The panel voltage isn't much higher than the battery voltage so there is little to be gained there and the controller is already limiting current flow anyway to stop voltage run away, so even if the MPPT could extract another 5% it can't be used because the voltage limit has been reached, the 5% plus more is being left on the table because the battery can't accept it without increasing the terminal voltage.

You have to look at the whole picture, not just a snapshot of information, but I think you may have already mentioned that

T1 Terry
Another long post picking particular conditions to suit the argument for PWMS
Yes ,IF you have large solar input compared to capacity used or battery bank capacity ,you may well get that situation of over voltage ,not true SOC, due to battery internal resistance .Nothing startling new about that particularly with LAs
Just another case of picking an unusual situation to try to justify the PWMs
BUT strangely "???"PWMs will see those batteries as fully charged also ,so what is the point ?????
YES , one does have to look at the whole picture , that means comparisons over a large range of identical conditions./[batteries panels weather etc] not just a few picked conditions that suit the required outcome
So many variable that few amatuer experimenters could ever hope to produce meaningful results .
Thanks Dibs, there has been some reluctance to post that sort of information ,so others could understand how so much can be run from lithiums
Good to see you had the room to fit over a 1000W of panels,probably more like 1500W! since they would be flat mounted ,& you are only using PWMs

The difference is Peter, I have actually carried out the experiments, you have just read about what tests have been done, picked the bits you liked and never bothered to look at the solar conditions associated with the test results. As long as it matched the theory it must be correct, if it doesn't match your view of the theory then it's all nonsense. The pioneers that put forward the ideas that you now call laws didn't just read about it, they were hands on and had others hands amateur experimenters confirm or challenge the findings. Unfortunately these days the actual hands on testing has given way to reading glossy sales brochures and parroting them off as fact without actually testing the theory is relevant in the local conditions. Just because something works where the panels are packed in snow and ice doesn't mean it will work where the panels have very little cooling bolted flat to the RV roof. That 20mm gap is between the panel frame and roof but the panel itself is surrounded by the frame so no air actually flows across the underside of the panel does it? As heat rises the heat is trapped under the panel, forget about infrared thermometers, actually tape the thermistor to the back of the panel and you'll get a better idea just how hot the panel really gets...... then do the math regarding the drop in Vmp per degree in the information supplied by the panel manufacturer and you will realise the parts that have been missed in the theoretical gains that can be made using an MPPT controller.... it's just not there unless the panels are connected in series and that produces its own losses, so then those losses must be included.

It doesn't matter a scrap to me what controller you want to use, my control box interfaces with any of them, granted some better than others as some have very crude voltage sensing to save money by not adding separate battery voltage sensing but rather use the battery charging cables to read battery voltage and anyone with a basic electrical understanding knows why that is not a good method of voltage control. The only reason I say that PWM is better than MPPT is from hands on testing, it comes out the same every time, over the full days charging the PWM is well ahead of the MPPT, some who did question my findings and actually did hands on testing themselves came up with the same result. A couple of those converted MPPT believers were ex PMG techs who worked all their lives with batteries in remote exchanges, if they were actually convinced from their own testing you are leaving yourself on a bit of an island Peter as you don't actually have any results from your own hands on testing do you?

T1 Terry

oldtrack123 · Guru

T1 Terry wrote:
[1][The difference is Peter, I have actually carried out the experiments, y
[2]As long as it matched the theory it must be correct, if it doesn't match your view of the theory then it's all nonsense
[3. ]The pioneers that put forward the ideas that you now call laws didn't just read about it, they were hands on and had others hands amateur experimenters confirm or challenge the finding
[4]nfortunately these days the actual hands on testing has given way to reading glossy sales brochures and parroting them off as fact without actually testing the theory is relevant in the local conditions
[5] Just because something works where the panels are packed in snow and ice doesn't mean it will work where the panels have very little cooling bolted flat to the RV roof.
[6]That 20mm gap is between the panel frame and roof but the panel itself is surrounded by the frame so no air actually flows across the underside of the panel does it? As heat rises the heat is trapped under the panel, forget about infrared thermometers, actually tape the thermistor to the back of the panel and you'll get a better idea just how hot the panel really gets...... then do the math regarding the drop in Vmp per degree in the information supplied by the panel manufacturer and you will realise the parts
[7]6]that have been missed in the theoretical gains that can be made using an MPPT controller.... it's just not there unless the panels are connected in series and that produces its own losses, so then those losses must be included.

[8]7]very crude voltage sensing to save money by not adding separate battery voltage sensing but rather use the battery charging cables to read battery voltage and anyone with a basic electrical understanding knows why that is not a good method of voltage control.
[9]The only reason I say that PWM is better than MPPT is from hands on testing, it comes out the same every time, over the full days charging the PWM is well ahead of the MPPT
[9],Some who did question my findings and actually did hands on testing themselves came up with the same result.
[10] you are leaving yourself on a bit of an island Peter as you don't actually have any results from your own hands on testing do you?

T1 Terry

Well, lets see

[1] limited experiments ,none of which have ever been shown or explained ,so the extent , accuracy, etc, is totally unknown

[2] Some people just hate theory, because they do not understand it. Just what they think they have learnt from the internet

[3]Yes, that i is right,Many MANY experiments over time & verified by their PEERS & continuously being PROVEN to this day

[4] Amazing how some people only refer to glossy brochures but ignore ALL the REAL scientific work that has & is being done by qualified people in the field

[5]I doubt that many test are carried out in snow fields

Such are usually done under CONTROLLED scientific conditions

[6] Of course If you stick or fix panels directly to the roof ,they will not cannot get air flow underneath .even the dumbest should understand that!!

Yet THAT is exactly what some who point out the heat effect do

I had a small motor home with limited space for panels due to 3 roof vents plus the fridge roof vent

I Knew about & found the heat effect way back when I had my first portable panels & 4wd pop top camper[back around the 1980s]

When we got the motor home,I made sure I DID OT bolt the panels directly to the roof I mounted them on a frame that kept the bottom of THEIR frame about50mm clear of the van roof,Plenty of FREE air flow underneath

also had an ampmeter permanently wired in,so I could always see what Amps I was getting & I know that method was very effective. That was in the mid 90s so I m not new to solar

[7] Those loss are minimal,if all done correctly & as far as the reg is concerned the series arrangement means LESS heat loss in the reg & the effect of shading is no worse if the panels have by pass diodes[shade tolerant ]

[8]Only applicable to LIs.Again An example of picking the situation

[9] Some ?? Perhaps they had preconceived ideas .& what exactly does that mean

10] you are correct I would not attempt to prove one way or the other for the simple reasons already outlined .There are too many variables to consider & control during such experiments that is beyond backyard experiments .I would rather go with work done by real experienced persons in such fields

T1 Terry · Guru

The kids would say to such .... "Whatever" but I think I'll attempt to reply to this put down
1) I have no reason to publish my experiments or results Peter, I think you will find very few actually do that these days unless they were paid via a public grant, even those paid by a commercial enterprise don't publish their testing or results because that information belongs to the commercial interest that paid for the testing, surely you can understand how that works.
2) An advanced diploma in electrical and computing technology (not completed due to a motor vehicle accident) gave me a quite solid grounding in the theory Peter and an average high grade pass mark of over 90% sort of proved I understood it as well. It also pointed out that many things accepted as law were later found to incorrect, electron flow is a great example and the description of an anode and cathode of course depends on electron flow doesn't it?
3)A few hundred systems out there in actual Aust conditions sort of back up I know what I'm talking about, how about yourself Peter?
4) Some examples of what has actually been done in Australia under full Australian conditions? Test carried out in far colder climates aren't relevant to Australian conditions, even the Morningstar engineers were willing to accept that on an open webinar, you should try dropping into them some time and see if you can get up to speed
5) shows you have not actually bothered to look into the testing conditions at all so all you think you know from what you have read do not relate to extra low voltage battery charging
6) umm.... no idea who you are referring to there Peter, maybe a bit more information rather than innuendo eh
7) was rather interesting Peter, based on ......... your assumptions I presume as most of the other stuff that is being passed off as knowledge by those who really don't know anything other than what they have read. You have difficulty in understanding the principle of heat trapped under the solar panel frame itself, how is 50mm clearance between frame and roof of a flat mounted panel going to create airflow to the underside of the panel, actually, just what forces will create an air stream under the panel, heat rises it doesn't flow sideways or down does it?
8) Are you serious Peter, you can't understand how that would effect any battery chemistry.... maybe the kids are right, no point in arguing with someone who simply doesn't grasp the situation so bases their argument on something that they don't actually understand
9) I think this is self explanatory Peter
10) I think we go back to the original problem, relying on what has been read without tunnelling down to find out how these results were achieved, using test results in conditions not normally found in Australia makes such results only viable for the climate they were tested in and that is not the high temperature environment found in Australia

T1 Terry

oldtrack123 · Guru

T1

Your attempt is pathetic.

Lots of words with little substance

Perhaps you should declare you have a financial interest in maintaining your "reputation"

"T1 Lithiums" Victoria

So must continue to push the same barrow that you started some years ago!!!

-- Edited by oldtrack123 on Thursday 13th of October 2016 11:04:34 PM

T1 Terry · Guru

Keep smiling Peter, and it's T1 Lithium in Mannum South Australia, my wife's business but yes I do the testing and development so my testing is continually ongoing and products have to prove themselves, I don't simply accept what it says in the sales brochure. After 5 yrs of continual development do you really think I wouldn't be using MPPT controllers if they really did do what are the marketing hype says they can?
I have always maintained that there are a few true MPPT controllers that do actually work, Outback Power and Midnite Solar, but at over $1,000 for a genuine unit (the Chinese knock off doesn't come even close) and the physical size puts them out of the picture for most RV installations. You would need a very big system for the $1,000 outlay to be value for money, the same $$ will buy quite a few more solar panels and result in a better over all output for the $$ spent

T1 Terry

macka17 · Guru

Lots of hot air going on there hey.

I had 2 x 110a AGM Chinese (as most are) battery's.
one 30a Regulator and 320w of panels on roof.

Ran my van for 13 yrs all over Eastern Seaboard and top end.

Never ran out of juice and 99% of time. Battery's floating by lunch.

ALso reg, and panel/s on Patrol/ute.
Same thing apart from batt's being Wet cell.

Same but smaller system in this rig.

I wouldn't know what an MPPT or the other one was.

nor the yet any advantage of super exxy Lithium for our application
in the real financial world,
when others do same job at fraction of price.

Lithium will come in later. when pricing reduces.
They no real advantage yet.

It's A bit like HONDA Generators and TOYOTA vehicles are the best I think.
In some eyes.

The only real advantages in any of this.
Is that MONO panels are bettereer (more efficient)than other types.

And a generator fixes ALL power supply problems.
when mated to a decent charger and a can of petrol.

NO MATTER what type of Charger... chuckle.

Enjoy yourselves. I'm going to move new lounge around for DI.

T1 Terry · Guru

The important part is the system works for your lifestyle, not that you have to limit your lifestyle to stay within the confines of your system. That is the real measure of added solar and lithium is for you or not, if it all works with capacity to spare and you are happy to fall back on a generator when you need to and the batteries live long enough to keep up with the $$ spent then that is all you could ask for really.
Not everyone fits into the same mould, some are happy to live by the battery monitor, some may find that they could travel a lot more if the better half wasn't forced into camping style living when away from home. Let's face it, who is it that has to put up with the limited use when on the road of all they have available at home at the flick of a switch? The old saying still rings true, happy wife means a happy life ;)

T1 Terry