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MPPT controllers , fact or fiction

 
pollinator
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I have been buying medium range (price wise)Chinese controllers, and finally after looking at the readouts for a long time and sure I must be missing something I'm starting to suspect these "MPPT" controllers are really just PWM.

I look at the voltage and amps for example,  36    1.5 under the PV output, then i go over to the next readout marked batt and see12.6 v  1.5A

I was under the impression that I should be seeing more like 3 amps going into the battery.

I thought that was the whole point, to step up the amps when excess voltage wasn't necessary

Maybe there is something screwy with the readout,  I do have a cheap multimeter, but  never think about it when I can find it, or I don't have batteries for it. like right now, I have no idea where the meter is

Regardless of the final outcome, screwy readout or bad controller,  has anyone else noticed these controllers aren't all they say they are?

In looking to put up a reference link to my controller, I noticed this in the description     "3, MPPT+PWM charging modeļ¼ˆController Provided  MPPT Maximum power point tracking Function,charging mode is PWM)  Anyone have an idea what this means?

here is the item (I have a 60A one)

https://www.ebay.com/itm/LCD-10-20-30-40-60A-12V-24V-MPPT-Solar-Panel-Regulator-Charge-Controller-GK-/401708805592?var=&hash=item5d87b5edd8
 
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Hi Bob. Pulse width modulation is used for current controlling.  I use it to control hydraulic valves with magnetic coils.  It is dynamic, because it is pulsing and this keeps a valve dithering to reduce hysteresis. The longer you leave the pulse on the more amperage for a given load and voltage.  Almost all modern controllers for mobile equipment that I use are pwm.  I do not know if these mppt controllers you speak of can doing that.  It is easily done with modern electronics and it would control amperage. A good meter will have a hz setting so you can see if it is pulsing.  
 
bob day
pollinator
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MPPT has been out for some time, in theory it takes extra voltage and turns it into amperage, according to the maximum power point- the voltage that will charge the battery best according to state of discharge and temperature

I don't think my meter has any sort of pulse detection, even if I could find it, but I do want to at least verify the output amps to the battery are identical to what I'm reading on the controller.

I'm getting ready to buy another controller for a separate refrigerator system, and am trying to figure out whether the extra expense of an MPPT is worth it.

I did read an article the other day, an oddity that suggested the MPPT technology had it's own problems and many would do better with PWM, but that may have just been opinion or special circumstance.

At any rate, with 36 volt panels, it only makes sense to have a 24 volt controller, inverter and battery bank and not rely on the MPPT technology as much., guess it may be time for an overhaul of my 12v system if I want to make the most out of the new panels
 
Christopher Shepherd
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We run all 12v too and the 12v panels are getting expensive compared to the 24v ones.  We run 2000w solar and 800w wind.  We stay with 12v for safety around the farm.  I have converted a bunch of things on the farm to 12v.  Even if the mppt works there is always loses.  I fully agree with your numbers.  I think 4 amps is closer to reality considering 36 v 1.5 amp is the same watts as 12v 4.5 amps.
 
pollinator
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I'd be careful buying cheap MPPT  solar controllers. Many of them are fake.





 
bob day
pollinator
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I thought I was actually paying about what an mppt would cost, I have three now, 30,60,80 amps, all look about the same as that fake, and like I commented earlier there seemed to be no multiplying effect of the amps, so coupled with your evidence I guess I need to either buy  all new controllers, or start running a 24 volt system to maximize what I'm getting from the panels. I may take one apart later.

16 volts is generally considered an average charging voltage for a 12 volt system, so likely the most I could expect is double, and with normal losses, I had considered 3amps a bit optimistic when the panel was putting out 1.5 (the panels were still snow covered this morning)  , still there should have been some amp increase if it's doing the job of an MPPT

I have been a great fan of Chinese tech,and some of the prices are obviously so low that they can't be accurate descriptions,  but these particular controllers that I bought are not that cheap.

Am I going to have to put every inverter on an oscilloscope to see if they are pure sine wave?

Buying tech just got a lot more difficult.

On the other hand, guess I don't need to find my multimeter right away :-)
 
pollinator
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Let the buyer BEWARE.    China really does not have enforcement of piracy of other tech out there, and much of it is fake,  that said there are some very good products as well.    I look for reviews on the seller before I buy, and I also check youtube to see who bought it before I did.     I will look for the seller of on youtube of units that prove to be good.


 
pollinator
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Regardless of the moral virtue of the sellers, electronics from China, ie, most consumer electronics these days, has a serious failure rate. That includes video cameras, radios, timers, battery chargers, moniters, thermostats, just about anything with a PC board in it. I went through three items in one week last year, a video camera, an ASUS high end router favorably reviewed by wirecutter.com and a usb hub. The router and camera cost me a full day each because they appeared at first to work and there was NO reason for their problems.

Thus it makes sense to search not only for what you think you want, but also for vendors with a large number of feedbacks on Amazon and similar sites. You can't always avoid problems, but it's worth a little due diligence. Amazon is the biggest and the most likely to have many comments and it allows you to go straight to the bad reviews and read through them. Sort by date so that you're starting with the most recent and hope to find 6 or more comments w/in the last year; older than that they mean much less because things change... What you're looking for is multiple reports of the same or very similar problem - that is your red flag. Then you decide whether you time is worth taking a risk on that product.

Amazon and similar large sites are good for another reason - enough problems with a product and they won't stock it. That takes a year or more, but it helps a little. Another thing to look for, on Amazon at least, is the actual seller. If it's Amazon it means that they have found that product to be worth their handling it, to not cause a lot of problems. They keep the gloves on and the name off for the hundreds of vendors listing on their site but selling from other sources.


Rufus
 
bob day
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Thanks for that extra heads up, I went ahead tonight and bought an EPever controller, a name brand, good history, found it on amazon and ebay for the same price, and it should do much better using the power from the panels.  I think I've been wasting about half the available watts with the bogus mppt controller I currently use, but I may be able to salvage it and use it in a 24 volt battery bank which will waste much less, although likely still not as good as having a good controller.

All that being said, I am amazed at just how expensive the stuff around solar panels has become.  And with high failure rates , bad circuit boards, and outright fraud, it would seem the Chinese have learned the greed of capitalism all too well.

I saw one controller ad bragging that after two years they would refurbish the controller  and guarantee it for another two years.  Don't do me any favors, charging as much as they did for that service after only two years of use for something that should last twenty years with no service.  Seems they have taken poor materials and quality control to a whole new level, where it is normal to expect things to fail, so you have to pay protection money to make sure they don't break down.



 
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A pwm charge control is a pwm charge control with or without mppt.

Mpp tracking identifies the voltage and current profile that would yield the most energy anytime there is sufficient voltage overhead and operates the array at that point until it shifts, tracks and goes again on intervals, sometimes tailorable and way programable for good ones. Otherwise the array is operated at battery voltage.

On a simple pwm, when the control is off you should see the array, when it is on you should see the battery voltage on the array circuit.

Accurate current meters on a 20$ controller? Id like to see it, but i imagine some are good.
 
bob day
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None of my mppt controllers have an on off switch to separate out the mppt function, but I'll tuck that info away for future reference

what you are saying helps me make sense of a description I recently saw using both mppt and pwm designations for the same controller.

After watching some of the technical videos describing how to recognize the innards of a true mppt controller, I took apart the 30 amp one I have that is not currently in use.  It did not have the large coil which is the hallmark of an mppt unit, so is falsely labeled.

I did however, in exploring different analyses of several other cheaper controllers, find that a couple of them actually are mppt, and some are up to 93% efficient.

Another encouraging thing, the pure sine wave inverter I'm using seems to be reputable, several positive reviews, and one where there was an oscilloscope hooked to it. The worst comment was a shipping mistake where the guy got a 48v instead of the 60volt unit he had ordered.
https://www.ebay.com/itm/2500W-12V-24V-48V-DC-to-110V-120-220V-AC-Pure-Sine-Wave-Inverter-Remote-control/142757108689?hash=item213cfc9bd1:g:VeIAAOSw3upa0YHT:rk:182:pf:0&LH_BIN=1
 
frank li
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By "off" i mean not charging, on full or other mode. You can press off, if it has an off. Not mppt off, control power forward, set to off. If it does not have the function you can wait till full. You will see pv voltage rise to voc because the controller disengaged the array input. If the array voltage is the same as battery voltage, the control is "off" or at least the array input portion is, in order to cut forward power to zero.

Im not having any useful knowledge of electronic architecture in there and this is based off of operation manuals and direct observation.
 
frank li
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Find that meter!

Frank.
 
bob day
pollinator
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These "mppt" controllers of mine were not that cheap, and have readouts for everything automatically displayed--pv voltage and amps,  charging battery voltage and amps, battery load voltage and amps

It has been pretty easy to monitor stuff, and I have suspected for some time they were not mppt, but guess I was reluctant to admit to myself the possibility I had been swindled

I found one meter, but it seems to be dead, I stalled out/ got distracted trying to find a small screwdriver to replace the battery, but   also need to find a battery....
 
frank li
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frank li wrote:By "off" i mean not charging, on full or other mode. You can press off, if it has an off. Not mppt off, control power forward, set to off. If it does not have the function you can wait till full. You will see pv voltage rise to voc because the controller disengaged the array input. If the array voltage is the same as battery voltage, the control is "off" or at least the array input portion is, in order to cut forward power to zero.

Im not having any useful knowledge of electronic architecture in there and this is based off of operation manuals and direct observation.



Made a mistake writing.
Should be;

You will see pv voltage rise to voc because the controller disengaged the array input. If the array voltage is the same as battery voltage, the control is (ON).

Editing snafuti.
 
bob day
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I think I understand what you are saying, but mine basically has two readouts for array voltage- one is just raw voltage and amps at the array, one is voltage and amps going into the battery from the array

The first raw voltage is always reading about 36 with amps varying with sunlight, the second is the adjusted voltage to the battery from the array with the amps varying   with pv amps if battery is discharged, but when bat is fully charged the amps will drop to zero, then off and on in a sort of float pattern.
 
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