mppt vs pwm

Hi Mr. Wizard,

It still shows that in bulk mode (when pwm would not be switching at all) that MPPT did 20% under totally unrealistic conditions.

Or am I wrong about pwm being non switched in bulk mode?

12thgenusa wrote:

JiminDenver wrote:
So what the graph says is the closer the input voltage is to the output the better. Wait, that's what I said pages ago. lol

Where on the graph would CA's 91v be or even something in the mid 40's going down to 12v?

Really, that's all you get out of it? Look again.

This particular controller cannot take greater than 60-v input. You would have to look at the specs for whatever controller CA has.

Wellll

I see that the 17-12 has the advantage over 34-12 until 20a and the 34-24 has the advantage through out. Then again there is a reason I prefer side by side testing. Who knows if a tech drew that up or the advertising department. I'm betting on the latter.

Concerning the "20%" question.

It is the difference between the 48 amps, from a 12v series/mppt set-up JiminDenver has seen reported, and the 60 amps he would expect to see from his own 24v parallel/mppt set-up. 48/60 = 80%. Do I have documentation? No. Is it a fair comparison? I can't say for sure. But Jim has proven to me to be a reliable source of information. And I'm quite convinced he's aware of all the factors that need to be considered when making such a comparison.

Pretty much everyone agrees there are many things to be taken into account. And as to the reliability of what is being reported on the various solar forums, I cannot say. But I also cannot attest to the reliability of much of what is said here on this forum, or by those in the retail industry.

Hi Salvo,

So if the input to the controller is 33 volts does charging start earlier than if it is 16.5?

Does MPPT keep the voltage higher than the 12 to 13 volts surface for longer if the set point is 14.8?

Salvo wrote:
For the majority of solar users here, the battery has the lowest SOC in the morning. At time there isn't enough irradiance to pump 30A into the battery. The battery will charge at perhaps 10A where charge controller efficiency is low. Surface charge will quickly increase battery voltage from say 12V to the 13V region, resulting in lower charge current.

If someone wants to web search for comparison data
They would do well to stick to sites dealing with off grid small installs

Ignore anything to do with grid tie

Equipment sellers love paper data, it closely corresponds to grid tie use

RV installs, simply do not represent the efficiency and paper gains, that equipment MFG and sellers want to advertise, they want the big bucks residential grid tie market

If I ever repair my blue sky 2000e
I might rewire a couple of my panels in series and try it out .
two of my panels in series are above. The stated voc of the 2000e, so I always ran them in parallel mode, now that the Xantrex C40 is installed
I can test the blue sky with a series pair, when I get around to repairing it
So far the C40 is doing better than I expected and about par with the 2000e for daily winter output, will see what happens as the days get longer and spring gets here

Personally until I have my own tests , I will go with the opinion that series panels early morning and lower irradiance wake-up, offset any possible minor efficiency loss compared to parallel panels
Any real loss efficiency of series is going to be do to shading issues reducing the output of the string, and that will depend on panel design regarding bypass diodes

BTW.. for real world RV use from a full-time RV solar user
Check out this thread of mine More solar for us

I don't update as often as I used to, almost daily for the first two years
But it documents the install and use, recording solar yields
Sunny hot cold wet dry foggy overcast traveling and parked year round recorded dated.
I log my solar in a daily planner, everyday, even when not updating the thread
Yesterday Monday Jan 12, yielded 76.0 8 amp hrs...1015.1 watt hrs
Saturday Jan 10, 29.34 amp hrs...383.9 watt hrs rainy and overcast

505 watts, thin film , frame mounted flat on roof

Website charts and numbers would say I should have had a total of about 5 hours of my panel value or 2500 watt Hrs
Yeah in my dreams...Maybe on a Grid Tie system tracking the sun...Maybe

You are cherry picking and it has everything to do with low irradiance in the morning.

Yes, your discussion is about the controller. But it's nonsense discussing efficiency at max PV output when that only happens on a blue moon. For the majority of solar users here, the battery has the lowest SOC in the morning. At time there isn't enough irradiance to pump 30A into the battery. The battery will charge at perhaps 10A where charge controller efficiency is low. Surface charge will quickly increase battery voltage from say 12V to the 13V region, resulting in lower charge current.

12thgenusa wrote:

Not cherry picking at all. This has nothing to do with mornings, low irradiation, battery surface charge or what panels one has. This is about controller efficiency at various voltages.

I think the entire thing is a mute point in regard to that video
It's not MPPT vs PWM
The title clearly says MPPT vs shunting
A shunting controller turns on and off it diverts power to the SHUNT ( a big resistor) to lower the voltage
MPPT is oh so far advanced above shunting , as crossbow is above clubs
So yes it's going to show a big increase..
But shunting is not PWM
He evens talks about the shunting controller turning on and off
Look how tiny that thing is
It's the wrong comparison
Sorry Don..You picked the wrong video

We're having this big discussion about MPPT gains and series panels
And that video is comparing ancient shunting technology

I've found out a long time ago that a person can be told the answer you're looking for over and over (which is the case here), and not comprehend, until you figure it out yourself. Put your thinking cap on!

pianotuna wrote:
Hi Salvo,

Please do tell me why 4 amps vs 5 amps is not 20% more?

JiminDenver wrote:
So what the graph says is the closer the input voltage is to the output the better. Wait, that's what I said pages ago. lol

Where on the graph would CA's 91v be or even something in the mid 40's going down to 12v?

Really, that's all you get out of it? Look again.

This particular controller cannot take greater than 60-v input. You would have to look at the specs for whatever controller CA has.

JiminDenver wrote:
So what the graph says is the closer the input voltage is to the output the better. Wait, that's what I said pages ago. lol

Where on the graph would CA's 91v be or even something in the mid 40's going down to 12v?

Hmmm. So 17.0V in and 15.0V out for top charging my Trojan T-1275... where does that put me at for efficiency, vs 17.0V in 12.0V out?

There is some fallacy there if you don't know what the actual output voltage setting is for your charge controller, IMHO.