PWM and MPPT connected to the same battery bank

[rvlifer]

Because that energy is hard won just to pee it away.

You mean like when i use it to watch tv or play games on my xbox?

 

[DonTom]

Because that energy is hard won just to pee it away.

Especially when there is no benefit of being less efficient.

-Don- Reno, NV

 

[rvlifer]

No, it's to regulate the TIME it is on.

-Don- Reno, NV

Seems a lot in the weeds to me.

"PWM is useful for controlling the average power or amplitude delivered by an electrical signal. The average value of voltage (and current) fed to the load is controlled by switching the supply between 0 and 100% at a rate faster than it takes the load to change significantly. The longer the switch is on, the higher the total power supplied to the load."

https://en.m.wikipedia.org/wiki/Pulse-width_modulation

 

[DonTom]

You mean like when i use it to watch tv or play games on my xbox?

Or to sit on your BFA outside your RV, reading or whatever, as I am out hiking.

-Don- Reno, NV

 

[DonTom]

Seems a lot in the weeds to me.

What do you mean by that? As you can see below from your own link there is no change in voltage or current, only time, in milliseconds, with PWM:

-Don- Reno, NV

 

[Mark_K5LXP]

PWM is how incandescent light dimmers work.

Mark B.
Albuquerque, NM

 

[DonTom]

PWM is how incandescent light dimmers work.

Mark B.
Albuquerque, NM

Yes, and many other things these days, such as variable speed motors (includes EVs to the 3-phase motor). It has a lot of advantages over regulating voltage & current. Much more efficient than most other methods. But MPPT is even more efficient than PWM where it can be used.

-Don- Reno, NV

 

[rvlifer]

What do you mean by that?

6 of one 1/2 dozen of another?

 

[DonTom]

it's possible to see that as a form of ripple on the battery.

I think we need definitions here.

Pulsating DC will not reverse polarity. It will all be either above zero or below zero volts. It can reach zero, but cannot change from negative to positive or vice versa. This is good to charge batteries with, regardless of the waveshape such as with PWM if it is designed to not go to the reverse polarity.

"Ripple" will include going to the reverse polarity. This is bad for charging batteries if too much of it. Best to have as little ripple as possible to charge batteries.

I made a mistake to use the word "ripple" when I meant pulsating DC in message number 8. I was thinking of pulsating DC when I used the incorrect word "ripple." Ripple implies true AC riding on the DC and is not wanted on batteries.

-Don- Reno, NV

 

[Mark_K5LXP]

"Ripple" will include going to the reverse polarity.

Per the google:

What is a ripple in electrical terms?

A ripple is defined as the fluctuating AC component in the rectified DC output. The rectified DC output could be either DC current or DC voltage. When the fluctuating AC component is present in DC current it is known as the current ripple while the fluctuating AC component in DC voltage is known as the voltage ripple.

Ripple is the correct term, just no polarity reversal.
Mark B.
Albuquerque, NM

 

[DonTom]

Ripple is the correct term, just no polarity reversal.

Yeah, I guess this was one of the many times I thought I was wrong--but was as right as usual.

But more seriously, how would you define pulsating DC compared to ripple? But perhaps it depends on where or who asked:

************************************************************************

-Don- Reno, NV

 

[Mark_K5LXP]

I guess in my world (electronics) there isn't much AC ripple to be found. It's always what's referred to what you might find riding on DC, whether that's from rectified AC you'd find on a supply or noise on a switcher. In the context of a solar controller or converter, the battery assures the DC level, from there it's system capacity and impedances that drives the P-P amplitude of whatever's there.

Since I have it handy, check this out:

This is a chinesium 9V lithium battery I got off amazon. Yep, sawtooth ripple out of a battery. It has some kind of switching converter/regulator built in. As it gets loaded, the ripple changes until you get these spikes:

I was hoping to use these on a couple QRP rigs I have but I'd have to build a filter for it as big as the battery. So much for that plan.

Mark B.
Albuquerque, NM

 

[DonTom]

find on a supply or noise on a switcher.

I have found that the cheap pure sinewave "switchers" put out more OTA QRN garbage than the cheap MSW ones do (unless you pay the big bucks, for the industrial use ones). I assume it's because the cheaper pure sinewave ones have more oscillators at ham band frequencies.

-Don- Reno, NV

 

[No cats]

I assume it's because the cheaper pure sinewave ones have more oscillators at ham band frequencies.

I worked in RF and spent many hours hunting for the sources of spectral noise in receivers. I also spent many hours in the lab analyzing transmitters. Typically, there is one crystal oscillator biased to one frequency. Great care is taken to keep this crystal stable under temperature, vibration, acoustic and other external influences. This is the clock to all frequencies in the system. Sidebands of this frequency are used to generate the channels used throughout the transmit and receive system. Because one oscillator is the source for all channels, the system is called coherent in frequency and phase. So noise in a HAM radio is nothing like noise in an power supply.

Power supply noise is more of switching effect generated by the switching itself. In a sine wave, there is only one frequency, but in a square wave, there is an infinite number of frequencies. the sharper the rise the more frequencies. The problem with some of the inverters having too much noise is inadequate filtering. That is why the good ones are so expensive.

 

[Mark_K5LXP]

Having done switch mode supply qualification I can offer that it's not a multiplicity of oscillators that's the problem, it's the switching transients generating broadband or wandering grunge (PedroDog's point). Even dumbe switchers running at a single freq can be MHz at the fundamental, so even just third or fifth harmonic energy can be pretty strong both radiated and conducted. Smart switchers will vary frequency and width based on load, ostensibly to improve efficiency (how you get from mid 90's to upper 90's) but then the grunge wanders around everywhere. Prudent PCB layout and output filtering can mitigate this nearly entirely. I tested some that with the standard connection setup (groundplane and isolated scope) the noise was barely more than the noise floor in the scope. Contrasted to the parallax in my itasca, that I can hear whistling away in the RV's AM radio. So if you're hearing a SMPS or solar controller it's not the topology, it's the cost reduction that eliminated shielding, bypassing and filtering.

Mark B.
Albuquerque, NM

 

[DonTom]

In a sine wave, there is only one frequency, but in a square wave, there is an infinite number of frequencies

What I am comparing are cheap modified squarewave (why lie?) inverters to cheap pure sinewave inverters. Why do the cheap pure sinewave inverters put out more garbage OTA than the cheaper MSW inverters? At least that has been my experience with my many inverters of various types around my ham radio receivers.

Yes, I do well understand that a perfect squarewave will have infinite odd harmonics unlike a pure sinewave which has no harmonics. While the cheap pure sinewave inverters have a much cleaner output, they put more garbage out OTA.

And I also understand the switching will make a lot of OTA noise. But why the difference between them?

-Don- Reno, NV

 

[Mark_K5LXP]

unlike a pure sinewave which has no harmonics.

The output might be a sine wave but what's inbetween - the switching of 12VDC into transformers or inductors to create that 120V sine wave is anything but a sine wave. Picture all manner of square waves and switching transients at MHz rates to keep magnetics small and throw that cacophony into an unshielded box produced at lowest cost. Some of that energy will leak out or get coupled onto the output, and there's your QRM QRP rig.

It works the other direction too with 120VAC to 12VDC converters and power supplies. If it isn't a giant blob of copper and steel inside then it's a switcher, and a harmonic generator. If you look at most any modern AC powered device to include things like laptop supplies, wall warts for phones or whatever they're nearly always "universal input", say 100-240V. What these do is take "whatever" voltage and frequency (50/60Hz, often DC too) turn it into DC, then switch/chop/boost/buck that into the final output voltage. These too can be little EMI/RFI generators though generally through economy of scale and having to meet international standards (CSA, UL, ETL, CE, Part 15 et al) some degree of shielding and EMI mitigation is in place so it's not noticed so much on consumer stuff.

Mark B.
Albuquerque, NM

 

[DonTom]

the switching of 12VDC into transformers or inductors to create that 120V sine wave is anything but a sine wave.

Yeah, but is there more switching going on in the cheap pure sinewave inverters than the MSF inverters?

Have you also noticed the big OTA differences between them?

-Don- Reno, NV

 

[Mark_K5LXP]

this voltage is not changed by the controller, it is instead PWM modulated. ... the voltage output of a PWM is typically higher than that of an MPPT.

I get why you would say that, as MPPT is actively controlling output while the PWM is turning on raw panel voltage. But, it's the battery that will limit that voltage at first due to the disparity of panel vs battery impedance even with the controller full on. Once the battery approaches 100%, the voltage monitoring in the controller will make those 'on' pulses ever shorter and the battery will integrate that to a relatively stable voltage. That voltage is what's used by the controller, along with whatever time/charge phase control it has to determine pulse width or any charge at all. Controllers typically have no awareness of battery size or active loads, it merely monitors terminal voltage and applies charge until specific voltage thresholds are reached and timers are satisfied. Because controllers ideally apply the same charge profile for a given chemistry and topology no matter what brand/model they are, multiple controllers will (should) more or less follow each other to charge a battery to completion. Plus or minus some tolerance and nuance of operation but they'll all converge at the 100% point, and the box is checked.

Mark B.
Albuquerque, NM

 

[Mark_K5LXP]

is there more switching going on in the cheap pure sinewave inverters than the MSF inverters?

Strictly brand/model/feature dependent.

Mark B.
Albuquerque, NM