Solar regulators, MPPT

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.

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

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.

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

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

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

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