MPPT Controllers

[cereal tiller]

Trying to figure out why there is such a huge difference in the prices of MPPT and PWM controllers

 

Am looking for an MPPT unit for a 1200 watt solar array,I know why the MPPT is superior as regards performance, higher voltage,thinner cables etc........

 

But the cost is disproportionate

 

CT

[reg]

The trend in solar panels is to produce higher voltage panels with lower amperage but these require a MPPT controller to work effectively. The main advantage of this set up is that charging will still take place in lower light levels ie when a pwm has given up the ghost the MPPT will still produce some charge.

It's a big subject oft visited but in simple terms

High voltage panels with lower amps and a MPPT controller will produce charging current in low light situations.

 

You do pay a premium initially but reep the benefits many times over particularly in low light situations eg winter time

 

Hope this helps

Edited August 10, 2016 by reg

[cereal tiller]

Thanks Reg,as I said ,the performance merits are obvious,but, why the Tenfold increase in cost?

 

Double the cost of a PWM might make sense?

 

CT

[WotEver]

Cos they're much more complex. Plus... the manufacturers can get away with it. ?

[reg]

Thanks Reg,as I said ,the performance merits are obvious,but, why the Tenfold increase in cost?

 

Double the cost of a PWM might make sense?

 

CT

Because they are much more sophisticated in what they do

As regards the cost with a large array, such as found on houses, they do not add significantly to the price as a proportion of the over the array cost however with smaller arrays they do present a much higher proportion of the total cost. So its very much a judgement call based on personal requirements.

 

On a budget it's tempting to go for a larger wattage panel and save money by using a PWM Alternatively you could go for a cheaper lower wattage panel and use a MPPT controller this allows for future expansion.

My preference is for the second approach I think once you have used a proper MPPT it is difficult to go back to a PWM

 

Again it all depends on your projected future array size the rule of thumb, which I think has been mentioned earlier, is above 150w MPPTs start to become cost effective.

 

 

Just on other point to consider there are many fake MPPT controller about just because it has mppt on its casing does not mean it is an mppt in many cases they are PWM with a MPPT sticker on them. Seek recommendations for controllers within your budget I personally use Tracer, of which I have 2, these are true MPPT at a reasonable price. Got mind from Bimbles

Hope this helps

[Guest]

Is it possible to parallel two identical MPPT controllers across the same battery bank, or is it asking for problems?

Cheers.

[reg]

Is it possible to parallel two identical MPPT controllers across the same battery bank, or is it asking for problems?

Cheers.

Now my head is hurting

 

If you mean can you have multiple mppt controllers going onto a battery bank then the answer is yes. I have 3 separate controllers going into a single bank of 4x110 batteries. Only reason it is like that is because of the historical way I have added to the system

[nicknorman]

Trying to figure out why there is such a huge difference in the prices of MPPT and PWM controllers

 

Am looking for an MPPT unit for a 1200 watt solar array,I know why the MPPT is superior as regards performance, higher voltage,thinner cables etc........

 

But the cost is disproportionate

 

CT

 

I think you're right, the cost is disproportionate to the performance benefit. But not to the complexity.

 

A PWM controller is just an electronic switch. Switch stays on until the battery voltage reaches the regulated voltage, then switch is turned on and off rapidly so as to maintain the battery voltage.

 

With a MPPT the device has to measure the voltage and current going into the battery, work out the product (the power), know the panel voltage, pull a variable amount of current from the panel so as to achieve a certain panel voltage, step that leccy down in voltage from say 100v to say 14v (with concomitant increase in current) using a switch mode Buck converter (involves inductors, fast power diodes and transistors), whilst slowly sweeping the current taken from the panel so as to sweep the panel voltage whilst measuring the output power and, if the trend in the output power is down, sweep it the other way to achieve the max power, whilst not becoming confused when a shadow/cloud suddenly changes the max possible panel output. Phew, pause for breath!

 

The other thing to consider is that it is not just the cost of the controller, it is the cost of the whole thing including the panels. So if you could spend £50 on a PWM, or £200 on an MPPT which gives 30% more power, that might seem bad value until you consider that you would have to spend a lot more than £150 on more panels for the PWM controller to match what you would have got with the MPPT. And that presumes you have enough roof space to add those panels.

Edited August 10, 2016 by nicknorman

[KJT]

Is it possible to parallel two identical MPPT controllers across the same battery bank, or is it asking for problems?

Cheers.

As reg above has said, yes it is possible. If your panels are pointing in different directions, in a 'pitched roof' arrangement on a roof box for example, or one panel is in shade and another in full sunlight, then having each panel go through dedicated a MPPT controller will be more efficient. Though not neccessarily cost effective.

 

Ken

[reg]

Yep that about covers it Nicknorman if I could precise that

PWM =Benny from Crossroads.

MPPT=Steven Fry

Edited August 10, 2016 by reg

[Guest]

Now my head is hurting

 

If you mean can you have multiple mppt controllers going onto a battery bank then the answer is yes. I have 3 separate controllers going into a single bank of 4x110 batteries. Only reason it is like that is because of the historical way I have added to the system

Yes that was what I was meaning. Thanks for that, it may be a good solution for me too

As reg above has said, yes it is possible. If your panels are pointing in different directions, in a 'pitched roof' arrangement on a roof box for example, or one panel is in shade and another in full sunlight, then having each panel go through dedicated a MPPT controller will be more efficient. Though not neccessarily cost effective.

 

Ken

Cheers, some food for thought

[reg]

Just to add one more thought into the mix

When do you most need charging? my answer over winter and in low light levels

Which set up is best geared towards giving me some charging over winter? My answer high volt low amp panel with a MPPT controller

 

These apply to my requirements different circumstances may produce different answers which is why there can never be a definitive answer to this oft repeated question

[cereal tiller]

Cos they're much more complex. Plus... the manufacturers can get away with it.

Thanks Tony,as I explained in the OP,they differences between the 2 types are obvious,it is just the price difference that defies logic.

 

Big gap in the market for an MPPT with a sensible price tag?

 

 

CT

[Murflynn]

Thanks Tony,as I explained in the OP,they differences between the 2 types are obvious,it is just the price difference that defies logic.

 

Big gap in the market for an MPPT with a sensible price tag?

 

 

CT

you get what you pay for.

 

there are lots of MPPT controllers on ebay for less than £30 - except they're not.

there are lots of genuine MPPT controllers on ebay for upwards of £70; in my book that's a fair price for what is, after all, a non-essential item but one which is worth paying for if you have the cash - and not exactly expensive if you invest, say, £400 in a solar system and want maximum performance.

 

why does the price difference defy logic? - the differences between the two types have been explained exhaustively.

[spadefoot]

The Tracer models that Bimble sell are not bad value. On a 1200 watt array you could use a pair of 40amp models. Much cheaper than a single 80amp model.

[cereal tiller]

The Tracer models that Bimble sell are not bad value. On a 1200 watt array you could use a pair of 40amp models. Much cheaper than a single 80amp model.

Came to that same conclusion after looking at Bimble's site,all my Solar Panels and Batteries came from them

 

CT