Solar regulators, MPPT

Submitted: Sunday, Apr 04, 2010 at 16:53
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I am thinking of installing a MPPT ( Blue Sky Solar Boost 2512i) to control the power from a 64w uni-solar to two 100ah deep cycle gel batteries. My concern is interference from this unit, and I quote;” The design of high frequency circuits can be very tricky because the problems with portions of the circuit "broadcasting" just like a radio transmitter and causing radio and TV interference. Noise isolation and suppression becomes very important". Do these units, MPPT’s, provide their own suppression or is it something else I have to worry about, like CB radio, engine management; wireless accelerator etcetera?
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Reply By: Dennis Ellery - Sunday, Apr 04, 2010 at 17:55

Sunday, Apr 04, 2010 at 17:55
An MPPT hasn't much advantage in full sunlight – they perform better at low light levels and are more suited to places like Europe. In Australia you will get a bigger bang for your bucks if you put your excess cash into a larger panel and a standard PWM controller.
AnswerID: 411643

Follow Up By: Member - Boobook - Sunday, Apr 04, 2010 at 18:55

Sunday, Apr 04, 2010 at 18:55
I disagree.

I have a MPPT and for the first few hours, when the temp is cold ( panel voltage high) and the battery low, I get about 13.2A of charge for several hours from 170W of panels. That is equiv to about 260W of panels at that time. Right when you need the extra charge. The worse the conditions ( low battery, less average light,etc, the better you are off. They are only about 5 - 10 % more efficient than PWM when you get the most from the sun anyway.

You can get MPPT chargers for about $80 now. Try buying 90W of solar panels for that.
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Follow Up By: Maîneÿ . . .- Sunday, Apr 04, 2010 at 20:37

Sunday, Apr 04, 2010 at 20:37
Dennis
Yes, I will agree with you for the reasons you have stated.
(hope this one is a short thread)

Maîneÿ . . .
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Follow Up By: Dennis Ellery - Monday, Apr 05, 2010 at 01:30

Monday, Apr 05, 2010 at 01:30
BooBook
You should ask for your money back.
When the voltage is high I get more than that with a PWM controller.

Mainey
We agree at last - it was only a matter of time.
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Follow Up By: Member - Boobook - Monday, Apr 05, 2010 at 05:07

Monday, Apr 05, 2010 at 05:07
Have you ever seen an MPPT operate in real life?

Doesn't look like it from your comments.

Dennis, if you agree with Mainey, you need to seriously reconsider your logic :-)
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Follow Up By: Maîneÿ . . .- Monday, Apr 05, 2010 at 10:22

Monday, Apr 05, 2010 at 10:22
Boobook,
What *exactly* is it you don't agree with or maybe understand ??

Maîneÿ . . .
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Follow Up By: Dennis Ellery - Monday, Apr 05, 2010 at 11:11

Monday, Apr 05, 2010 at 11:11
BooHoo,
There’s no need to attack poor old Mainey for something I’ve said.
I’m not going to debate technical issues with you, when you need to resort to personal attacks to win an argument.
Dennis
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Follow Up By: Member - Boobook - Monday, Apr 05, 2010 at 17:07

Monday, Apr 05, 2010 at 17:07
Dennis you would be well advised to read your own posts. I give up, you can believe what you like.
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Follow Up By: Maîneÿ . . .- Monday, Apr 05, 2010 at 22:04

Monday, Apr 05, 2010 at 22:04
Boobook,
You say: "I have a MPPT and for the FIRST FEW hours, when the temp is COLD and the battery LOW, I get about 13.2A of charge for several hours from 170W of panels. That is equiv to about 260W of panels at that time. Right when you need the extra charge. The worse the conditions (low battery, less average light, etc, the better you are off. THEY ARE ONLY about 5 - 10 % MORE EFFICIENT than PWM when you get the most from the sun anyway"


What possibly many people don't appear to understand is you don't actually *need* the 13.2 Amps you generate from your system, I say that because my system develops similar maximum current and my system powers a fridge/freezer which draws probably double the Amps of most 12v fridges (mine is 240v compressor) however my AGM battery system is fully charged by mid morning.
Once the agm battery system is charged, the solar system powers the fridge all day till nightfall, and then the agm battery system takes over again and powers the fridge/freezer and accessories during the night, next morning the solar system once again powers the fridge/freezer and recharges the battery system again.

The photo I put up in the locked thread clearly shows 12 Amps is being produced by the solar system, 5 Amps is charging the agm battery system and 7 Amps is running the fridge, all this is @ 11.20am, confirming what I've posted above.
(the *charging voltage* of the agm battery system is 14.3v)

The battery system does not need exorbitant numbers of Amps to recharge *ALL DAY* but as you have said "only the first few hours" from then on the battery system is only on trickle charge.

Maîneÿ . . .
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Follow Up By: Member - Boobook - Tuesday, Apr 06, 2010 at 05:23

Tuesday, Apr 06, 2010 at 05:23
Mainey, sorry. I won't waste my time on you anymore. Believe what you want. I really suggest that you take a basic electronics course to grasp the fundamental concepts.
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Follow Up By: ModSquad - Tuesday, Apr 06, 2010 at 06:45

Tuesday, Apr 06, 2010 at 06:45
Mainey, Dennis,Boobook,

please take your arguments else where. You have done nothing but hijack Wooltons thread with arguments over your own solar prowess. Take your banter off line as you are adding nothing of further value here.

First and final warning.

The moderation team.
Moderation is just rules

Lifetime Member
My Profile  Send Message

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Reply By: Battery Value Pty Ltd - Sunday, Apr 04, 2010 at 17:56

Sunday, Apr 04, 2010 at 17:56
Woolton,

any MPPT will generate some electromagnetic radiation, but this depends on a couple of things:

first, the amps in and out of the controller. Because your panel is small, the currents carrying the high frequency energy are also relatively small.
Secondly, if your controller has been c-ticked chances are the interference will be minimal because the manufacturer would have added filtering circuits.

If you do get disturbing interference, put the controller into on/off regulation mode which will stop any interference.

BTW, for such a small panel, the added complexity and money of a MPPT isn't really worth it because the gains aren't there to justify this.
It's probably more feasible buying a little larger a panel and have a simple on/off, or PWM regulator.

Best regards, Peter
AnswerID: 411644

Reply By: greybeard - Sunday, Apr 04, 2010 at 23:16

Sunday, Apr 04, 2010 at 23:16
If you have the specifications for the solar panel and the effiency of the MPPT charger you can do your own maths to work out what you may and may not gain by replacing the common switching regulator woth an mppt.
for the example i've chosen a BP380 panel panel spec here and a mppt12-1 mppt spec

I've derated the typical mptt effiency from the manufacturer from 97% to 95% to allow for real life.

I'm also using 14.5V as the charging voltage ( because it fits with the mppt spec and this isn't a discussion about charging voltage ).

Panel max pwr = 80W
Voc = 22.1V
Isc = 4.8A
Vmaxpwr = 17.6V
Imaxpwr = 4.55A

Battery charge Voltage = 14.5V
MPPT effiency = 95%
You need to understand the difference between a switching regulator and an MPPT.
Basically a switching regulator will connect then disconnect the power source to the load to maintain an average output voltage for a series regulator. Or for a shunt regulator, it will switch a short circuit on and off across the power source. To prevent the load being shorted out it is typically isolated by an electronic device that only allows current to flow from the source to the load.
In this case the solar panel is the power source and the battery is our load.

What this means is that for a switching regulator the maximum current we can possibly get from the solar panel is Isc ( 4.8A ).
At 14.5V ( the load voltage ) and 4.8A we get ( P = V * I ) 69.6W, not 80W.
We've lost some power during the period that the panel isn't connected to the load.
A MPPT uses some electronic smarts to adjust the load on the solar panel to try and maintain it at it's maximum power point to extract the maximum amount of power from the panel as it can.
The circuitry of the mppt transers power by adjusting both the voltage and the current as it passes through the regulator. There is a lot of information available on the web if you are interested in the theory of how an mppt works.
Bottom line is with an mppt we operate the panel at it's max power point and have the full 80W going into the mppt. The mppt effiency ( power transfer ratio ) is 95% so we get 95% of our 80W at the output ( 76W ). A gain of 6.4W or just over 9% increase in power.
With our power law ( P = V * I ) we have 76W = 14.5V * 5.25A available to charge our battery.
Note the increase in current, greater than both the max pwr current and the Isc.
At lower illumination levels you will get a greater increase in power output with the mppt than a switching regulator. You'll need to get some solar panel data to see this.
Most manufacturers of mppt's seem to specify an effiency gain over a std regulator over a period somewhere around 25-30%, in the fine print they suggest that ~20% is average. My feeling, not backed up by any real data, is that i'd expect 10% and any more is a bonus. ymmv
Is it worth getting a mppt instead of another panel? With the theory above, the price of a solar panel and the price of a mppt you can determine this yourself.
AnswerID: 411665

Follow Up By: Maîneÿ . . .- Monday, Apr 05, 2010 at 01:39

Monday, Apr 05, 2010 at 01:39
That is a lot of assumptions

Typical 80 Watt panel has an operating voltage of ~17.6 volts, delivers 4.55 amps
( Volts x Amps = Watts - 17.6 x 4.55 = ~80 )

To compare a MPPT reg with an on/off switching reg is like comparing today’s technology with a T model Ford.
You correctly state you "loose some power during the period that the panel isn't connected to the load" because the on/off reg is not connected some of the time, that’s why you should compare a reg with constant charging capabilities, they are not disconnected from the battery and your numbers are then irrelevant.

The MPPT versus series regulated question is not always straight forward as it very much depends on the conditions under which charging is taking place.

Be aware that the % gains claimed for MPPT are not likely to be ‘real world’ because the hotter the panels become, the maximum power point voltage de-creases and gets closer to a typical battery voltage, therefore wiping out most if not all, of any gain an MPPT unit will give.

MPPT's are most effective under COLD conditions, so when used in WARM weather you definitely don't get the claimed benefits at all.

Maybe you can gain 25% by adding a MPPT in cool conditions, that does not help you much if your MPPT is only 85% efficient because you've only gained about 5 watts, which nothing at all to get excited about, because an efficient regulator would have done that anyway.

Maîneÿ . . .
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Follow Up By: greybeard - Monday, Apr 05, 2010 at 10:11

Monday, Apr 05, 2010 at 10:11
i disagree with the incorrect rewording and technical inaccuracies in the reply above.
All data quoted can be found in the manufacturer's source documents that are available by following the links provided in the original reply.
I'd strongly suggest that anyone with any vague interest in this subject perform their own research and reach their own conclusions.
Please note that it is possible to exclude words as well as include them when you use most search engines. for example you could search for 'mppt regulator' -waffle.
This would give you results that contained the words mppt and regulator and exclude results that include waffle.
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Follow Up By: Maîneÿ . . .- Monday, Apr 05, 2010 at 11:37

Monday, Apr 05, 2010 at 11:37
greybeard,
If you disagree, how about you simply *copy/paste* what you believe to be the “incorrect rewording and technical inaccuracies” the bits and parts that you don't understand or agree with, and I'm positive it can be clarified just for you :-)

As you say some of the information you have posted is available from the "manufacturers source documents"... so using your very own analogy, the information available from every single snakefish oil web site is also then correct too?
That implies HyClones and the 'fuel pill' works work 100%, simply because the manufacturers web site says they do, so it must be true and correct (not)

Do you think the manufacturer will really print the fact that MPPT's are most effective under C00L conditions, that they will then in fact then loose some of their claimed benefits under H0T conditions, no, they only tell you what they want you to read that will SELL their product.

I’m not saying they don’t work at all, I’m saying you have to put up ALL the facts, not just the obvious benefits, please tell it as it is and state the negative points also.

Maîneÿ . . .
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Reply By: greybeard - Monday, Apr 05, 2010 at 12:04

Monday, Apr 05, 2010 at 12:04
woolton
from what I can see of other people's reports with the blue sky controller there has been issues with RFI generation but the manufacturer has taken steps to address it.
I haven't seen any specification for RFI emmissions from an mppt ( or pwm controller for that matter ).
The majority of rfi reports seem to be with the boating people and they report varying levels of interference with HF radio.
It would depend on your intended use, ie HF during the day while the panel is providing power, if it may cause you any problems.
Perhaps some of the HF radio clubs might have some members with experience of mppt's with HF. Similarly some of the caravan clubs might help with the TV side.
If the mppt's generate any noticeable RFI you may find that your usage patterns don't overlap so it isn't a problem. ie charging during the day, tv/hf/radio at night.
I can't see any of the engine management being fazed by RFI.
cheers
gb
AnswerID: 411690

Reply By: _gmd_pps - Monday, Apr 05, 2010 at 12:13

Monday, Apr 05, 2010 at 12:13
I use two 200W Panels in series delivering up to 52V at 7.5 amps.
I use a Outback Power MB60 MPPT controller to take out 12V ..
only a MPPT controller can do that and it does not create any
interference with anything. I do not know about all
these people posting here and not having a clue about MPPT ..
again a typical display of exploroz knowledge..

good luck
gmd
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Follow Up By: Dennis Ellery - Monday, Apr 05, 2010 at 14:59

Monday, Apr 05, 2010 at 14:59
What brand panels have you got?
You should be getting a better output than that.
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Follow Up By: _gmd_pps - Monday, Apr 05, 2010 at 16:51

Monday, Apr 05, 2010 at 16:51
the voltage varies of course with sun exposure, on the secondary side I get between 13.4 and 14.4 (depending on charge phase) up to 32 amps.

Up to is the wrong wording .. I should have said typical ..
the panels deliver more at times (they are rated at 27V - 36V max) at 7.5 amps
but 52V at 7.5 Amps is pretty close to their capacity under "normal" circumstances and is what I have seen so far. I do not sit in front of the display and watch it all the time :)) ... it's mostly turned off anyway :)))

they are GE panels ... 150cmx95cm from US ..

have fun
gmd





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Follow Up By: Member - Boobook - Monday, Apr 05, 2010 at 17:16

Monday, Apr 05, 2010 at 17:16
Dennis Ellery posted:
What brand panels have you got?
You should be getting a better output than that.

My calculator says 52V and 7.5A is 390W. You couldn't expect too much more that that could you? What brand will deliver significantly more out of 400W panels?
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Follow Up By: Dennis Ellery - Monday, Apr 05, 2010 at 17:58

Monday, Apr 05, 2010 at 17:58
I get that sort of performance out of Sharp Panels with a PWM controller.
And have achieved more on one occassion that I know of, though I dont sit in front of the controller all the time.
I suppose gmd would have achieved more on the odd occassion too.
Cheers Dennis
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Follow Up By: Member - Boobook - Monday, Apr 05, 2010 at 21:00

Monday, Apr 05, 2010 at 21:00
Dennis, here is the news.

The output of a set of panels won't change regardless of the controller, PWM, MPPT etc. 200W is 200W is 200W is 200W is 200W under the same light and temp conditions.

It is the output of the CONTROLLER that is used to charge the batteries that is in question. MPPT controlers are 5 - 30% more effective in charging batteries in any condition and 20 - 30 % more effective in harsh conditions.
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Follow Up By: Member - Boobook - Monday, Apr 05, 2010 at 21:01

Monday, Apr 05, 2010 at 21:01
Dennis, here is the news.

The output of a set of panels won't change regardless of the controller, PWM, MPPT etc. 200W is 200W is 200W is 200W is 200W under the same light and temp conditions.

It is the output of the CONTROLLER that is used to charge the batteries that is in question. MPPT controlers are 5 - 30% more effective in charging batteries in any condition and 20 - 30 % more effective in harsh conditions.
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Follow Up By: Dennis Ellery - Monday, Apr 05, 2010 at 21:56

Monday, Apr 05, 2010 at 21:56
BooBook - I’ll agree to disagree.
Whilst you can take those sorts of figures as a guide, possibley better suited to light levels on the continent, you can’t beat actual test results under operating conditions. In my experience manufactures quoted efficiencies are best case scenarios and often don't come up to specification under heavy load conditions. The figures quoted by gmd shows he is getting a very good result from his MPPT. I get just as good from my PWM device.
You are happy with your MPPT controller. We are three happy little vegemites - what more could you ask for?
Cheers Dennis
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Reply By: Mandrake's Solar Power- Monday, Apr 05, 2010 at 13:25

Monday, Apr 05, 2010 at 13:25
My turn !!

Lets assume the MPPT controller works as it should then the very BEST result by any MPPT manufacturer would be to turn your 64watt panel effectively into an 83 watt panel for ONLY that part of the cycle when in BOOST mode .. If you look after your battery as a lot of people do that may NEVER happen ... Personally I would spend my hard-earned on a 100 watt panel or Kit OR as has been said above in places get a VERY GOOD QUALITY standard reg/controller .

( Lets see what that brings eh Mainey !! I'm retiring to the bunker now !! )

Cheers

Steve

AnswerID: 411699

Follow Up By: Maîneÿ . . .- Monday, Apr 05, 2010 at 20:29

Monday, Apr 05, 2010 at 20:29
Steve,
don't think you will need a bunker :-)
the tide appears to be turning with more ppl understanding solar a bit better

Maîneÿ . . .
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Follow Up By: Member - Boobook - Tuesday, Apr 06, 2010 at 05:31

Tuesday, Apr 06, 2010 at 05:31
This post has been read by the moderation team and has been moderated due to a breach of The Trolling Rule .

Forum Moderation Team
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Reply By: Woolton - Monday, Apr 05, 2010 at 19:14

Monday, Apr 05, 2010 at 19:14
Thank you all for sharing your thoughts and knowledge with me, it was very much appreciated. You have certainly given me something to think about.

Thanks again
Woolton
AnswerID: 411728

Follow Up By: Maîneÿ . . .- Wednesday, Apr 14, 2010 at 11:54

Wednesday, Apr 14, 2010 at 11:54
The Power Conversion Efficiency for the “Blue Sky Solar Boost 2512i” is;
97% - when rated @ “14v, 20 Amps”
What would it be @ <4 Amps that you have?
Acceptance Voltage: 14.2v "Fixed Value"
Float Voltage: 13.2v "Fixed Value"
Can't find a Bulk charge rating

The specifications for the MPPT12-1 are as follows;
15v to 55v - input voltage
13v / 14.5v - output voltage
150 Watts @ 14.5v - output power

The MPPT12-1 solar regulator has no alarm, no low voltage disconnect, no programming choices, no panel shorting and no surge protection either, but yes it’s cheap.

MPPT12-1 Link:

Maîneÿ . . .
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