Mppt controller

[luggsy]

Are these any good ? Does any one have one fitted ? http://www.ebay.co.uk/itm/262630165133?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[Stormbringer]

Don't know specifically BUT I DO know that they are NOT mppt controllers, just pwm ..

 

Plenty of info on YouTube.

 

Iirc the cheapest true mppt controller is about 75 quid and is, I think, German made.

 

Cheers

Andy

[Murflynn]

how is it legal for a trader in Leicester to offer goods which are not CE compliant?

 

does ebay not count as a trading method?

[Chewbacka]

how is it legal for a trader in Leicester to offer goods which are not CE compliant?

 

does ebay not count as a trading method?

Maybe because trading standards have had no complaints and so are unaware.

It is also not legal for ebay sellars to sell stolen or counterfeit goods...........................

[Richard10002]

how is it legal for a trader in Leicester to offer goods which are not CE compliant?

 

does ebay not count as a trading method?

The law, and rules in general, only applies to those who choose to obey it, and to those who get caught and prosecuted.

 

I see many people disobeying the law and various rules, but who don't get caught. Some actually have a manner about them which suggests that the law and/or rules don't apply to them.

[Chewbacka]

Don't know specifically BUT I DO know that they are NOT mppt controllers, just pwm ..

 

Plenty of info on YouTube.

 

Iirc the cheapest true mppt controller is about 75 quid and is, I think, German made.

 

Cheers

Andy

Depends upon how you define MPPT.

In the 'normal' system the panels are of a high voltage and the controller uses inductors to transform the voltage to a lower level.

In this case it seems it does find the max power point but then controls the flow of power into the batteries using PWM technology. The down side of this is you can not use big, cheap commercial panels as the open circuit voltage is too high. In this case for a 12v system the max OC voltage must be between 18~24V.

Personally I would get a big heavy controller with inductors.

[cuthound]

MPPT controllers use switch mode power supplies, which "turn the power on and off" at a very high frequency. You cannot do this quicky with inductors in the circuit, and the cost of the inductors will be uncompetitive.

[nicknorman]

MPPT controllers use switch mode power supplies, which "turn the power on and off" at a very high frequency. You cannot do this quicky with inductors in the circuit, and the cost of the inductors will be uncompetitive.

??? Please check out how switch mode power supplies work!

[WotEver]

Review of basically the same unit albeit a 20A version:

[cuthound]

??? Please check out how switch mode power supplies work!

I did.

 

"HOW A MAXIMUM POWER POINT TRACKER WORKS:

The Power point tracker is a high frequency DC to DC converter. They take the DC input from the solar panels, change it to high frequency AC, and convert it back down to a different DC voltage and current to exactly match the panels to the batteries. MPPT's operate at very high audio frequencies, usually in the 20-80 kHz range. The advantage of high frequency circuits is that they can be designed with very high efficiency transformers and small components. 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.

 

There are a few non-digital (that is, linear) MPPT's charge controls around. These are much easier and cheaper to build and design than the digital ones. They do improve efficiency somewhat, but overall the efficiency can vary a lot - and we have seen a few lose their "tracking point" and actually get worse. That can happen occasionally if a cloud passed over the panel - the linear circuit searches for the next best point, but then gets too far out on the deep end to find it again when the sun comes out. Thankfully, not many of these around any more.

 

The power point tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, running through a transformer (usually a toroid, a doughnut looking transformer), and then rectifying it back to DC, followed by the output regulator. In most DC to DC converters, this is strictly an electronic process - no real smarts are involved except for some regulation of the output voltage. Charge controllers for solar panels need a lot more smarts as light and temperature conditions vary continuously all day long, and battery voltage changes.

 

Smart power trackers

All recent models of digital MPPT controllers available are microprocessor controlled. They know when to adjust the output that it is being sent to the battery, and they actually shut down for a few microseconds and "look" at the solar panel and battery and make any needed adjustments. Although not really new (the Australian company AERL had some as early as 1985), it has been only recently that electronic microprocessors have become cheap enough to be cost effective in smaller systems (less than 1 KW of panel). MPPT charge controls are now manufactured by several companies, such as Outback Power, Xantrex XW-SCC, Blue Sky Energy, Apollo Solar, Midnite Solar, Morningstar and a few others".

 

The high frequency switching of dc-dc converters can only be achieved by transistor switching, aka switched mode power supplies.

[CaneyJ]

Definitely fake. The best affordable ones I've seen are these http://www.ebay.co.uk/itm/New-20A-MPPT-charge-controller-Tracer-2210A-20-Amp-EPSolar-/152238845429?hash=item2372246df5:g:30UAAOSwyjBW4D8xwhich are offered in 10A - 40Amps. Anything cheaper is a fake PWM.

[nicknorman]

I did.

"HOW A MAXIMUM POWER POINT TRACKER WORKS:

...

 

The power point tracker (and all DC to DC converters) operates by taking the DC input current, changing it to AC, running through a transformer (usually a toroid, a doughnut looking transformer), and then rectifying it back to DC,

 

MPPT controllers use switch mode power supplies, which "turn the power on and off" at a very high frequency. You cannot do this quicky with inductors in the circuit, and the cost of the inductors will be uncompetitive.

So I'm not quite clear if by your second post you are acknowledging that MPPT controllers do in fact contain inductors, or not? The article you quote is badly written and mentions "transformers" which are of course inductors, but in reality most SMPSs just use an inductor. Transformers might be used if it were necessary to fully isolate the output from the input, and I suppose (but not sure) it might be more efficient to use a transformer rather than a single inductor if the reduction of voltage required was very large.

 

Anyway, bottom line is that MPPT devices and SMPSs contain things with coils of wire, whether they be 2 terminal inductors, or transformers. If you disagree look up "Buck converter".

[Tony Brooks]

how is it legal for a trader in Leicester to offer goods which are not CE compliant?

 

does ebay not count as a trading method?

 

Simply because our lazy government will not get laws passed that makes the likes of Ebay, Amazon & co jointly libel for goods sold through their organisations.

 

Ebay and Amazon have also neatly removed the credit card protection on purchases form their sites because banks say it is not a direct credit card transaction but payment to a third party.

 

 

[cuthound]

So I'm not quite clear if by your second post you are acknowledging that MPPT controllers do in fact contain inductors, or not? The article you quote is badly written and mentions "transformers" which are of course inductors, but in reality most SMPSs just use an inductor. Transformers might be used if it were necessary to fully isolate the output from the input, and I suppose (but not sure) it might be more efficient to use a transformer rather than a single inductor if the reduction of voltage required was very large.

Anyway, bottom line is that MPPT devices and SMPSs contain things with coils of wire, whether they be 2 terminal inductors, or transformers. If you disagree look up "Buck converter".

I don't disagree and accept they use small inductors, and whilst technically a transformer is two inductors, most people think of coils as inductors, not transformers. Poor choice of words by me.

 

Whilst not trying to teach you to suck eggs, perhaps a little power supply history is required.

 

Prior to the introduction of fast switching transistors capable of handling a fair amount of power, (which form the basis of SMPSs) any power supply, inverter etc was huge, and relied upon large inductors to smooth out the low (mains frequency) ripple, as well as transformers to increase or decrease the voltage.

 

With the advent of suitably rated transistors, the switching frequency could go up by several orders of magnitude, permitting the inductive components to be downsized.

 

The transistors chop up the dc, which is fed into a transformer to transform up or down as required, and then rectifed back to dc.

 

Buck/boost work in the same manner.

[Top cat]

I've been using one of these

 

http://www.onboardenergydirect.co.uk/shop/BlueSolar-Charge-controller-MPPT-75-15-VBS75_15.html#SID=278

 

which is a MPPT controller for up to 200W ( they make bigger ones) for the past 3 years. I know its really a MPPT because it holds the panel, at its peak power point of 35V when the sun goes in or loads rise or fall. Current price just under £80.

 

Top Cat

[nicknorman]

I don't disagree and accept they use small inductors, and whilst technically a transformer is two inductors, most people think of coils as inductors, not transformers. Poor choice of words by me.

Whilst not trying to teach you to suck eggs, perhaps a little power supply history is required.

Prior to the introduction of fast switching transistors capable of handling a fair amount of power, (which form the basis of SMPSs) any power supply, inverter etc was huge, and relied upon large inductors to smooth out the low (mains frequency) ripple, as well as transformers to increase or decrease the voltage.

With the advent of suitably rated transistors, the switching frequency could go up by several orders of magnitude, permitting the inductive components to be downsized.

The transistors chop up the dc, which is fed into a transformer to transform up or down as required, and then rectifed back to dc.

Buck/boost work in the same manner.

Not really. Firstly in conventional (old fashioned) power supplies the main way of smoothing the rectified AC was with capacitors, although yes sometimes inductors were used too. Since the voltage conversion was done by the fixed turns ratio of the transformer and the actual rectified voltage depended on the load, linear regulation was used which was effectively a variable resistor in series. Dropped lots of volts, lots of A passing through = lots of heat dissipated = big heatsinks needed = big and heavy.

 

Smps don't use transformers to change or regulate the voltage - or at least, don't need to depending on the difference between source and output voltage. SMPSs work by having a reverse biased diode and inductor. When the transistor turns on, current starts to increase in the inductor (dI/dt = V/L). When the transistor turns off the inductor's nature (desire to preserve current) pulls current via the diode, voltage starts to droop. Transistor turns on again. Etc. So there is in theory at least, no resistive power loss, no heating etc. In practice there is a bit of switching loss when the transistor is in mid switch, ditto for the diode, and of course the inductor has some small resistance so it is not 100% efficient, but getting fairly close.

 

Edited September 19, 2016 by nicknorman

[cuthound]

Thanks Nick, I was under the impression that buck/boost converters were SMPS devices using tranformers, because in the industry I worked in, all smpss (1.4kw or more output) used tranformers as they were typically 50-400 volt DC power supplies.

[nicknorman]

Thanks Nick, I was under the impression that buck/boost converters were SMPS devices using tranformers, because in the industry I worked in, all smpss (1.4kw or more output) used tranformers as they were typically 50-400 volt DC power supplies.

I think it depends on the difference between the input and output voltages. Although SMPSs using inductors are fairly efficient, the efficiency decreases roughly in proportion to the difference between input and output voltages. So a mains powered 5v supply would probably use a transformer. Whereas a 12v to 5v one definitely wouldn't. In very high power supplies as you mention, efficiency will become very important hence the use of transformers rather than inductors.

 

I doubt MPPTs use a transformer since they have to be able to cope with a wide range of input voltages from say 100v right down to say 14v. If your panel is only putting out 14v you wouldn't want to have a transformer and as far as I know they are buck only, not boost-buck, since there would be virtually nothing to be gained by being able to increase a panel's voltage up to 13v or whatever since at that low a voltage it isn't really producing a significant amount of power.

 

Edit: simplified boost-buck converter: SW2 is left open and SW1 chopped to buck, SW1 left closed and SW2 chopped to boost. Just one inductor.

Edited September 19, 2016 by nicknorman

[tonyt40]

Are these any good ? Does any one have one fitted ? http://www.ebay.co.uk/itm/262630165133?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

The simple answer is no,not really. For a degree in MPPT see above?