MPPT controller - generating more power out than power in - nah ??

Submitted: Sunday, May 26, 2013 at 10:51

ThreadID: 102420 Views:3289 Replies:3 FollowUps:11

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KenInPerth

Hi all knowlegable ones - ponder me this over your Sunday coffee ...

I have just been reading bits on MPPT vs PWM out of curiosity and found this "amazing" demo which shows a couple of power meters ( I assume) on input and output of an MPPT vs a PWM controller - shows about 200% efficiency .. huh ??

MPPT power in power out demo

Now I am from an old school that says you cannot have more than 100% efficiency of any device so what skulduggery is going on here ?? I am guessing something is messing with the power meters to give wrong readings ?? I am not disputing MPPT controllers will give you more power to your batteries, but only by maximising the power derived from the panels for the conditions, not by producing more power out than is put in to them. Am I missing something ??

I think our electricity suppliers need to change to DC power and use these ... double out what they put in ... good profit margin in that ...

Another video (not with quite the same "power gain") here

MPPT vs PWM demo

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Reply By: Bazooka - Sunday, May 26, 2013 at 11:08

Reply By: oldtrack123 - Sunday, May 26, 2013 at 11:14

Sunday, May 26, 2013 at 11:14

Hi Ken
First you are correct ,there are always losses in energy when changing from one type to another
A basic law of physics
But you need to ensure you are using energy units for the comparisons
Amps are not a measure of electrical energy
WATTS must be used [Watts=VxA ]
In the case of MPPT controllers ,they take a higher voltage, lower current from the solar panels& CONVERT that into lower voltage ,higher current into the battery
e.g,t
200W panel is usually rated 200W AT around 17V=11.76A

Neglecting losses
That 200W INPUT to the controller will be converted by the controller to 200W divided by the battery voltage AT THAT TIME
If the battery voltage is 12V the CHARGE current will be 16.6A

Battery voltage 14V, Charge current=14.29A
The actual losses with a good MPPT is about 5%

PeterQ

AnswerID: 511847

Follow Up By: oldtrack123 - Sunday, May 26, 2013 at 11:26

Sunday, May 26, 2013 at 11:26

Hi
I cannot edit so will add
Such conversions go on all around us EVERY DAY with AC electrical Transformers
It is just that modern electronics make it very easy to do with DC power
In the past THAT was only possible with rotary converters

A PWM regulator does not have the capabity to convert
They only pass the actual solar amps into the battery

Using the SAME 200W panel

Battery at 14V x,amp11.7 =164.7W
Battery @ 12V xamps 11.7=140.4W
Battery flat @ 11V x11,7A =128.7W

PeterQ

FollowupID: 790133

Follow Up By: KenInPerth - Sunday, May 26, 2013 at 11:29

Sunday, May 26, 2013 at 11:29

Peter

Yes I understand and agree with what you are saying - hence the reason I posted this - for my own curiosity, for others experienecd opinions, and for the unwary that might believe it to be true.

If you look at the videos the meters show voltage, current, power, and watthours. And yes I did a quick mental check of the calculations based on the V and A shown.

The input meter shows about 29W and the output meter shows about 46W which we know cannot be right.

So my question is why?? Maybe someone that messes with this stiff every day knows - maybe a analogue meter would show something very different ??

FollowupID: 790134

Follow Up By: oldtrack123 - Sunday, May 26, 2013 at 12:25

Sunday, May 26, 2013 at 12:25

HI Ken
Many of of that bloke's post on a forum where he sells solar indicates he is a Magician
I do not believe he has an electrical background ,from other posts he has made on that forum
A little over 12m ago HE was asking questions on how solar worked!!
I had not watched the Video when I made my post, but now have
One point I picked up ,He is measuring while he has a fluctuating load on the Battery
I also noted the RAPID fluctuations in the readings
Perhaps he is reading battery load current in addition the solar charge current due to incorrect wiring
This can /does happen with incorrect connection using the LOAD terminals of ANY regulator
I have seen similar remarkable claims made on forums even with PWM regs

PeterQ

FollowupID: 790136

Follow Up By: KenInPerth - Sunday, May 26, 2013 at 12:49

Sunday, May 26, 2013 at 12:49

Had not considered that possibility - but yes .... and I did note the name Mandrake as Bazooka had pointed out.

The second video is a more "sophisticated" set up which I misinterpreted the first time - it is (looks like at least) the input to the MPPT from what he says and a better example showing clearly what you are saying and would expect from an MPPT - the power derived from the solar cells changes from 40W on PWM to 56W on the MPPT and the current / voltage changes are shown accordingly.

Unfortunately he does not show the power being delivered to the battery to compare the result there.

FollowupID: 790141

Follow Up By: Jason – Perth - Sunday, May 26, 2013 at 15:31

Sunday, May 26, 2013 at 15:31

Hi Ken,

Very interesting thread and video.
I don't think Mandrake is breaking the laws of physics.
I think we are looking at differences in sampling rate of the meters V's the switching rate of the regulators. Essentially, a sight frequency difference created a hetrodyning effect that will cause the meter to change readings as we saw.

I can't back that up just yet, but thought I would post as a possible theory?

Cheers
Jason

FollowupID: 790149

Follow Up By: Jason – Perth - Sunday, May 26, 2013 at 16:12

Sunday, May 26, 2013 at 16:12

That's a really bad choice of words!
I meant to say, as he can't break the laws of physics, there must be some error with the metering.
Jason

FollowupID: 790154

Follow Up By: oldtrack123 - Sunday, May 26, 2013 at 19:30

Sunday, May 26, 2013 at 19:30

HI Jason
That is a distinct possabilty
With the fast changes taking place

MPPTS actually do a form of impedance matching the panels to the load & do it by steps
WIth THAT, loads changing,& delays in digital meters responce time
the results are pretty meaningless
On top of that, Watts reading from each meter is just an instantaineous value
But the Magician seemed happy to use the figures obtained.

Why he did it with a load ion the battery is beyond me

I guess it is just another example of not believing everything the "expert" salesman tells you
Peter

FollowupID: 790165