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Post Info TOPIC: Pwm vs Mppt


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Pwm vs Mppt


Australia direct 4wd drive and camping everything 12 volt related, I just watched a little vid on this site called,

PWM vs MPPT charge controllers educational video,but. I cant post the link if anyone can find it and post it here I think it would be a very good thing thanks ....



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Is this the one?

 

https://www.australiandirect.com.au/video/pwm-vs-mppt-charge-controllers/?gclid=EAIaIQobChMIsJvw6Onw2gIVVB0rCh2cOAFZEAAYASAAEgIiDvD_BwE

 

I was worried that you were about to start up yet another one for the Tech heads debating, no arguing, about the relative merits of pwm v mppt.

 

I'll have a look at the vid now to see what it says.

 

edit (after looking at the vid) ...  Oops looks like I spoke too soon.  I think that the vid might just spark off the usual discussion.  BTW, I have a spare pwm controller that came with my Vic off Road panel. An mppt controller is built into my DC to DC charger so I didn't need the pwm one.


edit 2 ... here is a previous thread on the subject of pwm v mppt ... a lot of which I don't understand

  http://thegreynomads.activeboard.com/t64129951/pwm-or-mppt-controller/

              


-- Edited by Cupie on Sunday 6th of May 2018 08:21:30 PM



-- Edited by Cupie on Sunday 6th of May 2018 08:33:49 PM

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Thanks Cupie for the link I just wanted to see a tec report on the subject that was well explained and this one seemed to be right on the money ,theres no doubt in my mind now that mppt is is in a league of its own...



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Ron-D wrote:

Thanks Cupie for the link I just wanted to see a tec report on the subject that was well explained and this one seemed to be right on the money ,theres no doubt in my mind now that mppt is is in a league of its own...


 Hello Ron_D. Interesting video, thanks for putting it up. It does explain differences however, the parameters used are biased, probably based on pulling in more sales of a more expensive unit. Warning bells started in their opening sequence, showing figures for a 300w 24v panel whilst showing specs for a 120w 12v panel. A bit later he sprouts a very one sided example that suits mppt. If you are regularly running deep cycle batteries down to 11v as in their example you have a much greater problem of having to replace batteries.

Lastly, few people run 200w to 300w panels on caravans etc as it is not prudent to do so, and do not run 2000w.   Mppt's are used on large arrays such as on house roof installations where mppt is the norm.

It is just as possible to have an unbiased video with real life RV specs to show a more even difference between the 2 systems.

Joe



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Thanks Joe I see your using a pwm reg with your set up so obviously your happy with your reg,it would be interesting to see a report from a real techie on the subject,we have one here thats knowledgeable but he promotes pwm with his systems thats fair enough,but that goes against everything that I have read on the subject, it would be nice to hear from a techie that could give an unbiased slant on the Mppt reg ,I think from what I have read just about everywhere,most would use the more modern tec reg even on Rvs..



-- Edited by Ron-D on Tuesday 8th of May 2018 09:33:46 AM

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This post in the forum link that cupie quoted above pretty much covers what the lay person should be initially looking for.

.....................................................................
Quote
It has been shown, often, that the cheap MPPT regs like the one above are FAKES ! They may work OK as PWM regs but have no internals to boost the output current. furious There are lots of FAKES on ebay.

When I did my research the Tracer brand, available from a lot of suppliers on ebay and locally were the cheapest ones which actually work. I found mine worked well. They have a front meter to display some details and also have a remote meter available to monitor the functions, for a reasonable price.

Note that poor sized wiring will dissipate the extra power that they can make, in wiring losses.disbelief So if the wiring from the panels is minimal then just use a PWM reg and save the money.

Also note the MPPT reg current rating is based on the full solar power rating not just the panel current rating as the output current will be higher at some times.

Jaahn

PS I bought a cheap PWM reg recently for a simple job. It was advertised as a two stage reg but actually it was just a simple one setting reg with no float. They refunded a small amount to get it "fixed" when I complained. disbelief Plenty of fakes in the cheap end of the market !! I would not trust my expensive batteries to a cheapie.



-- Edited by Jaahn on Monday 20th of November 2017 08:28:56 AM
End quote
...........................................................

There is many a subjective argument for and against each controller.

T1 Terry has contributed some good information regarding the use of PWM controllers and others disagree with him.

Terry is an installer and appears to have done a great deal of research as to what he recommends.

Terry also appears quite knowledgeable if you are thinking lithium.

I am not in any way affiliated with T1 Terry, I just like the way he explains things.



-- Edited by Dickodownunder on Tuesday 8th of May 2018 10:50:55 AM

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Ron-D wrote:

Thanks Joe I see your using a pwm reg with your set up so obviously your happy with your reg,it would be interesting to see a report from a real techie on the subject,we have one here thats knowledgeable but he promotes pwm with his systems thats fair enough,but that goes against everything that I have read on the subject, it would be nice to hear from a techie that could give an unbiased slant on the Mppt reg ,I think from what I have read just about everywhere,most would use the more modern tec reg even on Rvs..



-- Edited by Ron-D on Tuesday 8th of May 2018 09:33:46 AM


 On my previous van I had a tech based in Adelaide that fitted 300w solar to 2 x 120 amp AGM's and I asked him about MPPT controllers and his view was that I was my money I was spending but for my situation the PWM would be fine.

His statement was that while MPPT was great on large house type installations the PWM would be fine on my set up.

I went PWM and it worked fine.

edit; just to make it clear I didnt use T1 Terry because I didnt know of him at that time however I believe Terry is a "real tech" as is the guy that fitted my solar.

Phone around and ask some "real techs" and form your own opinion from there.

If you have made your mind up on MPPT then buy a good unit and go that way.



-- Edited by Dickodownunder on Tuesday 8th of May 2018 11:04:07 AM

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HI
Quality Mppt work but donot have tobe a lot of dollars . My 30a MPPT EP solar --Tracer series low dolllars good performance . UNDER 200$
I maxed out my portable size otherwise to heavy 195w
I maxed out my fixed [no more realestate on roof ] 195w

In the real world panels donot always perform at 100% output all the time
SO
To get some performance back MPPT

400watts produces 22 amps +++ mppt 30% 28-29 amps [beware this only occurs when batt is more than lightly discharged]

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T1 Has designed his system around Li batteries, [Almost constant voltage]& Panels who's PPP is low & leaves little power for a MPPT to make use of

A rather complicated way to explain it is that his panels & Li batteries are very close to being IMPEDANCE matched which means the system is operating @ max performance


Impedance matching of sources to loads does require some advanced technical knowledge, not something that many average electricians would understand & of course T1 is not an electrician.



If you could keep the LA batteries fully charged little will be gained by a MPPT.
But LAs are a totally different story, with the voltage dropping as they discharge.

The question one needs to ask themselves is .:

What is the best way to go ,

[a]Add more panels IF you have the space & weight allowance & use a PWM or  the extra cost of a quality  MPPT??

Of course IF  if you do not  have the roof space or weight allowance that option is outbiggrin

HE is not comparing apples with apples!

Many of us have tried to explain that to him for a loooong time
A quality MPPT with suitable panels will ,overtime ,outperform a PWM. when used with LA batterries
The fact that every roof top solar system uses MPPTs is so they get the max available output from the panels



-- Edited by oldtrack123 on Saturday 12th of May 2018 05:25:41 PM

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Mmmm...
Real techs???

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Good post oldtrack thats a very good explanation.



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Ron-D wrote:

Good post oldtrack thats a very good explanation.


 I agree  .. except that I had to re read it a few times before I got it,   ie LA means Lead Acid.  Then it all made sense.

"Impedance matching" ... gee that term takes me back 1/2 a century or so when I used to try to teach barely understood principles to very un-interested trainees/apprentices.  The only way that you could gain their attention was to say 'now this would make a good exam question'.  Up would come the heads & they would start scribbling furiously for a bit before nodding off again.  Unfortunately I too had been just like them & only learned enough to get the 60% pass mark so my knowledge was paper thin. Add to that is that my memory is piss poor.

  



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If you don't read the newspaper you are uninformed.

If you do  read the newspaper you are misinformed!

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Cupie wrote:
Ron-D wrote:

Good post oldtrack thats a very good explanation.


 I agree  .. except that I had to re read it a few times before I got it,   ie LA means Lead Acid.  Then it all made sense.

"Impedance matching" ... gee that term takes me back 1/2 a century or so when I used to try to teach barely understood principles to very un-interested trainees/apprentices.  The only way that you could gain their attention was to say 'now this would make a good exam question'.  Up would come the heads & they would start scribbling furiously for a bit before nodding off again.  Unfortunately I too had been just like them & only learned enough to get the 60% pass mark so my knowledge was paper thin. Add to that is that my memory is piss poor.

  


 Hi Cupie 

You were a naughty boy  you should have worked harderbiggrin 

I had a good start in  my tech life

My father was an Electrician & radio mechanic

From a very early age I use to sit & watch him doing radio repairs Asking questions all the time & even reading his Radio magazines & books

All stood me in good stead when I started  my electrical apprenticeship , got honours or credits in every exams

I knew a lot more  about electronics than any  of the electricians or more senior apprentices & by my third year was  doing ALL the company's service work on products they sold  & they sold just about every thing for engineering 

such as :

resistance welders With timers

Electronic flame failure devices

Photo electrical devices

Instrumentation of all type 

Westinghouse /Mc Kensie & Holland rectifying equipment   

Westinghouse /Rosebery  switchgear & motor control systems ,electrostatic air cleaners  & many other of their products 

Brown & Boveri instrumentation  & controls 

& that is only about half the listbiggrin

 I also started doing an Electrical engineering  diploma course but after a few years had to give it up as I was on 24hr a day callout for the service work just could not handle it all & the company's Electrical Engineer & a director reckoned I was more a hands on person  [which was true] & that I had a job for life with the Co. 

That turned out to be true retired from them age 60Years ending up as a works manager



-- Edited by oldtrack123 on Sunday 13th of May 2018 12:59:58 PM

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Gone are the days of 'a job for life'.

I too was a single company person ...

Started at 15 1/2 yo and finished at 57 1/2 yo.

Had a great time working with great people in what was in those days a very good Company.

In the process I had at least 3 quite different careers all within the same organisation.

Started near the bottom of 60,000 + employees & ended up in the top 400 of admittedly a leaner organisation of about half that size.



-- Edited by Cupie on Sunday 13th of May 2018 10:18:04 PM

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If you don't read the newspaper you are uninformed.

If you do  read the newspaper you are misinformed!

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A few interesting bits in that video, the first bit @ 1.13mins shows a label from the back of a set of 3 panels that they sell. The specs are all STC ratings from a light box flicked on for a few secs and the panel temp at 25*C, yet a little further down the listing they show an NOCT of 47*C+/- 2*C so they are admitting the panel doesn't actually operate at 25*C yet they show no NOCT output readings, so you can take the outputs listed on the label with a grain of salt.
At around the 6 min mark it gets even more ridiculous, using their suspect figures the 100w panel will run at close enough to 100% efficiency. No MPPT manufacturer claims better than 80% panel efficiency, the 97% efficiency they spec is a cherry picked figure showing the difference between power in and power out, so they are really saying at the very best they are 3% inefficient or will waste 3% of anything that comes in .... and these are their very best figures, not the average or the worst, ya gotta wonder right there eh :lol:
The fact that no one in their right mind discharges their battery down to 11v regularly and the fact as soon as you start charging a battery it won't remain at 11v seems to be completely over looked.
A genuine video with 2 identical solar panels charging 2 identical batteries, one with a quality PWM controller and the other with a similar priced MPPT controller would show the reality rather than the nonsense, even swapping the batteries over between one and the other, then the solar panel between one and the other to clear up any doubts about one battery or panel being better than the other.
As far as using 24v or 36v panels to charge 12v batteries, why would anyone want to do that? You can't fit a grid tie solar array on the roof of a caravan that has a TV antenna, air con and a few vents fitted, so no point in pretending that you could buy them cheap and use them. Unless you can fit a decent array of large identical panels on your RV roof you can't connect them in series either, so no gain to be had with smaller cabling yet all the problems with high voltage feeding back into the panels and destroying them .... I have a few photos for those that don't believe it happens and I'd be happy to post them if anyone wants to see them.

T1 Terry


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oldtrack123 wrote:

T1 Has designed his system around Li batteries, [Almost constant voltage]& Panels who's PPP is low & leaves little power for a MPPT to make use of

A rather complicated way to explain it is that his panels & Li batteries are very close to being IMPEDANCE matched which means the system is operating @ max performance


Impedance matching of sources to loads does require some advanced technical knowledge, not something that many average electricians would understand & of course T1 is not an electrician.



If you could keep the LA batteries fully charged little will be gained by a MPPT.
But LAs are a totally different story, with the voltage dropping as they discharge.

The question one needs to ask themselves is .:

What is the best way to go ,

[a]Add more panels IF you have the space & weight allowance & use a PWM or  the extra cost of a quality  MPPT??

Of course IF  if you do not  have the roof space or weight allowance that option is outbiggrin

HE is not comparing apples with apples!

Many of us have tried to explain that to him for a loooong time
A quality MPPT with suitable panels will ,overtime ,outperform a PWM. when used with LA batterries
The fact that every roof top solar system uses MPPTs is so they get the max available output from the panels



-- Edited by oldtrack123 on Saturday 12th of May 2018 05:25:41 PM


 Really Peter? Are you sure you don't actually mean grid tied solar systems rather than all roof top solar systems? If you have 5kW or 10kW or 15kW of solar on your RV and feed it back into the grid rather than using it to recharge your batteries then listen to what Peter has to say. If you don't then ask to see Peters side by side actual real life testing that backs up what he is saying actually applies to RV size systems charging lead acid batteries.

T1 Terry is an Automotive Mechanical Engineer and part of that training involves extensive hands on knowledge involving the use of 12v and 24v battery systems. To get a 97% entrance exam pass into the Institute of Automotive Engineers and to hold that membership for over 20 yrs means you need to know a lot about DC voltage, wiring and batteries, very few licenced electricians would get a pass level in extra low voltage DC knowledge. That is where the problems seem to occur when an ex sparkie who spent most of his time in the office ties to apply what he thinks he knows to answer a question rather than applying knowledge he has gained actually testing his theories in a real life situation using the actual equipment used by the average RV owner. There is no value in using a controlled power supply as the input and a controlled load as the output to verify the value of any particular controller, you need to use actual solar panels and actual batteries to get genuine results.

 

T1 Terry

 

T1 Terry 



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T1 Terry wrote:
oldtrack123 wrote:

T1 Has designed his system around Li batteries, [Almost constant voltage]& Panels who's PPP is low & leaves little power for a MPPT to make use of

A rather complicated way to explain it is that his panels & Li batteries are very close to being IMPEDANCE matched which means the system is operating @ max performance


Impedance matching of sources to loads does require some advanced technical knowledge, not something that many average electricians would understand & of course T1 is not an electrician.



If you could keep the LA batteries fully charged little will be gained by a MPPT.
But LAs are a totally different story, with the voltage dropping as they discharge.

The question one needs to ask themselves is .:

What is the best way to go ,

[a]Add more panels IF you have the space & weight allowance & use a PWM or  the extra cost of a quality  MPPT??

Of course IF  if you do not  have the roof space or weight allowance that option is outbiggrin

HE is not comparing apples with apples!

Many of us have tried to explain that to him for a loooong time
A quality MPPT with suitable panels will ,overtime ,outperform a PWM. when used with LA batterries
The fact that every roof top solar system uses MPPTs is so they get the max available output from the panels



-- Edited by oldtrack123 on Saturday 12th of May 2018 05:25:41 PM


 Really Peter? Are you sure you don't actually mean grid tied solar systems rather than all roof top solar systems? If you have 5kW or 10kW or 15kW of solar on your RV and feed it back into the grid rather than using it to recharge your batteries then listen to what Peter has to say. If you don't then ask to see Peters side by side actual real life testing that backs up what he is saying actually applies to RV size systems charging lead acid batteries.

T1 Terry is an Automotive Mechanical Engineer and part of that training involves extensive hands on knowledge involving the use of 12v and 24v battery systems. To get a 97% entrance exam pass into the Institute of Automotive Engineers and to hold that membership for over 20 yrs means you need to know a lot about DC voltage, wiring and batteries, very few licenced electricians would get a pass level in extra low voltage DC knowledge. That is where the problems seem to occur when an ex sparkie who spent most of his time in the office ties to apply what he thinks he knows to answer a question rather than applying knowledge he has gained actually testing his theories in a real life situation using the actual equipment used by the average RV owner. There is no value in using a controlled power supply as the input and a controlled load as the output to verify the value of any particular controller, you need to use actual solar panels and actual batteries to get genuine results.

 

T1 Terry

 

T1 Terry 


 Oooh that nasty DC stuff , real electricians don't know about it ,but an auto mechanic does!!no 

There is it is folks NO Real Electrical experience , No electronics knowledge  ,  but Lots of knowledge about those very complicated things called batterries even the nasty 24V  ones.  And low voltage solar panels

Not even an Auto electrician.

I wonder when Terry will accept  that the basic electrical principles applies to EXTRA low voltage DC & are the basics of every electrical apprentices first year apprentice ship .

THAT is how complicated it is .And why no license is required to work on it.!!!

 

Terry does not like theory for one simple reason it is beyond his understanding,  as many of us have seen with his posts here & elsewhere

 

Terry , I have given you the compliment  of having experimented with & developed  a system that is very suitable for use with LI batteries.,  in the van & motor home situation , but the red herrings are jumping every where ,trying to escape from your posts.

Lots of words do not indicate real knowledge but are  commonly called Bull S*#t, though  they may fool those who do not  know /understand the real facts 

For those who do not know , T1 interest in Lis & solar started about 5years ago from memory

.Compare that with some one who has spent a life time dealing with  all types of electrical equipment ranging from  Extra low voltage Dc & Ac up to thousands of volts Dc & AC

On two other forum , he demonstrated his lack of basic electrical theory  & simply could not accept he was ever wrong

Those Forums have some very qualified people on them,  but T1 took the same attitude there as he does  here ,

In the end he was removed from those forums.

Every one who does not agree with him is denigrated ,no matter what their qualifications. 

 

PS I am not sure where you get the idea that I spent most of my time in an officeno   that is total BULL S--t 

 But I will repeat the compliment I made previously

T1 has EXPERIMENTED & developed a system that is very suitable with LI batteries , much of that is due to the relatively constant output voltage of LI s over their working range, plus panels  whose MPPT point leaves little  power for a MPPT to convert .

No Magic , No voodoo  just very simple  basic electrical principles. [perhaps beyond a first year electrical apprentice  but certainly should be well understood by 3rd year

-- Edited by oldtrack123 on Sunday 20th of May 2018 07:39:20 PM



-- Edited by oldtrack123 on Sunday 20th of May 2018 07:53:06 PM

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