Cheap MPPT regulator from China - true and not fake?

[bcroe]

Dereck, do you know if MPPT controllers are any less likely to generate RFI? We tried a few PWM controllers at some sites and they generated a lot of noise on 42 and 150 MHz.

The PWM controllers are inherent noise generators, because they rely on switching panel
current on and off. Then the panels act as a big antenna to radiate the noise. To a lesser
degree any other wiring will also radiate. Only a limited amount of filtering may be used
before causing too much heat.

An MPPT controller runs at high frequencies that can easily be filtered, if the mfg takes the
expense to do so. Current through the panels and other wiring should be essentially DC,
so radiated noise should be minimal. Failing that, external shielding & filters can be added
to this equipment to limit radiation. Bruce Roe

[Sunking]

Dereck, do you know if MPPT controllers are any less likely to generate RFI? We tried a few PWM controllers at some sites and they generated a lot of noise on 42 and 150 MHz.

They are both equally noisy as both use switching. Just a matter using a good controller with adequate filtering.

[sdold]

Dereck, do you know if MPPT controllers are any less likely to generate RFI? We tried a few PWM controllers at some sites and they generated a lot of noise on 42 and 150 MHz.

[Sunking]

I think those are good explanations. It reminds me of an engine that isn't allowed to turn up to max power rpm.
I'm sure there is a reason for 36 cell panels, but it seems like fewer cells in a smaller panel would be a better match.

Actually in the early days panels were only 32 cells for direct connection to batteries. Coleman still makes the mechanical relay on/off controllers for them. Shell Oil was the big name for them back in the day and the day and still in use today. Next time you drive down the road and see a blinking light with a solar panel chances are it is a 32 or 24 cell panel directly connected to a battery with only a Diode (Blocking) to prevent back feeding from battery at night graining the battery. Once PWM hit the market panel manufactures settled on 36 cells 18 volt as standard 12 volt battery panels.

Moral of the story rather you use PWM or direct connection you turn a 100 watt panel into a 66 watt panel. Only MPPT will allow you to use all the potential power from a panel. Once you go above 200 watt panel power using GT panels and MPPT is less expensive. It takes a 300 watt PWM system to = a 200 watt mppt system. A 300 watt PWM system will run you around $650. A 200 watt mppt much less around $400.

Only reason PWM and battery panels are still around is PT Barnum Effect. A Sucker Born Every Minute and the world is full of them with pockets full of cash.

[SunEagle]

I think those are good explanations. It reminds me of an engine that isn't allowed to turn up to max power rpm.
I'm sure there is a reason for 36 cell panels, but it seems like fewer cells in a smaller panel would be a better match.

Probably the "plus" side of 36 cell or "battery" panels is the ability to move them due to their size and weight. They allow you to build a small power center which can be easily broken down and moved. That is the one reason I built a system so it could be easily moved via my pickup or stored in my RV.

Then again while having mobility as a "plus" the big negative is the cost/watt. Also finding the "right" CC that matches up with those panels can be difficult.

[sdold]

I think those are good explanations. It reminds me of an engine that isn't allowed to turn up to max power rpm.
I'm sure there is a reason for 36 cell panels, but it seems like fewer cells in a smaller panel would be a better match.

[SunEagle]

True. It is nevertheless lost as a result of using the PWM controller. So we could say that it is lost by the PWM controller even if not lost in the PWM controller.

Or in other words "a percentage of what the panel wattage can produce is not being used by the CC to charge the batteries". I would put the blame on the PWM CC for the loss.

[inetdog]

I realized that, but you caught me before I was able to edit my point was only that power in and out of the controller is virtually the same. The power lost by using PWM isn't lost in the controller, it was never there to begin with because the panel wasn't allowed to develop it.

True. It is nevertheless lost as a result of using the PWM controller. So we could say that it is lost by the PWM controller even if not lost in the PWM controller.

[sdold]

What I said and meant was when the Vmp of the panel is higher than the battery voltage power will be lost..

I realized that, but you caught me before I was able to edit my point was only that power in and out of the controller is virtually the same. The power lost by using PWM isn't lost in the controller, it was never there to begin with because the panel wasn't allowed to develop it.

[inetdog]

How could a panel increase above battery voltage with PWM? The PWM controllers I'm familiar with only have a half volt drop or so across the switching device. The panel is pulled down to the battery voltage. P=IE, so the input power is the same as the output power, minus a small loss across the switch (0.3v for the Trace C series for example).

What I said and meant was when the Vmp of the panel is higher than the battery voltage power will be lost. For a given current the panel will have a corresponding output voltage. To get the rated power from the panel (under mythical STC conditions) you have to have the current and the voltage at Vmp and Imp at the same time.
A PWM controller will draw more current than Imp, dropping the voltage below Vmp and costing you energy.

[sdold]

PWM means current out = current in (minus a small amount to run the electronics). Very simple.
And that generally means power out from the panel is less than Pmax, getting worse as the panel voltage (Vmp) increases above the battery bank voltage.

The PWM controllers I'm familiar with only have a half volt drop or so across the switching device. The panel is pulled down to the battery voltage. P=IE, so the input power is the same as the output power, minus a small loss across the switch (0.3v for the Trace C series for example).

[inetdog]

I meant that I think the PWM controller power output is (about) the same as the input.

Edit: Disregard, I may have misunderstood your post, I think you were talking about panel STC power, not the controller input power.

PWM means current out = current in (minus a small amount to run the electronics). Very simple.
And that generally means power out from the panel is less than Pmax, getting worse as the panel voltage (Vmp) increases above the battery bank voltage.

[sdold]

Nope. internal losses. Best are 95% efficient. This one in the video has a sizable heat sink, and I expect it's not any better than 90%, if even that.

I meant that I think the PWM controller power output is (about) the same as the input.

Edit: Disregard, I may have misunderstood your post, I think you were talking about panel STC power, not the controller input power.

[Mike90250]

Aren't they power in = power out?

Nope. internal losses. Best are 95% efficient. This one in the video has a sizable heat sink, and I expect it's not any better than 90%, if even that.

[yewsuck]

Aren't they power in = power out?

Yes they are and should be if real. Minus Conversion Efficiency and the power to run the Controller. The internal electronics take power to work. Hence why the above poster said 250w in 200w out is MPPT.

-YS