Usefulness Of MPPT Technology

Mex

If I had your panels where I camp at high altitude I would expect roughly 24 amps peak. That's based on the output of my panel at 10,000 ft. Altitude and type of panel can really affect what you will see.

They do list efficiency on the MPPT controllers so one may do better than the other. Send me a Rogue 20a and I'll be glad to compare the output vs my Eco-worthy 20a side by side. ;) I wouldn't expect a huge difference between the two, The Rogues extra value is in build and features.

There's different ways to look at MPPT and it's worth. I've read that power wise it really doesn't matter if you are in a sunny location but that MPPT shows it's worth in lower light conditions. I have to agree because I see power before the sun breaks the horizon and in clouds so thick I can barely see where the sun is to aim the panel. The voltage may be lower but it still converts to 4-5 amps when I expected nothing at all. Not much you say? Well it was enough to keep us off the generator on a cold weekend in a dry campground.

Budget is another way to look at it. High voltage panels are cheaper than 12v but MPPT controllers are more expensive especially if you go with the pricier units. In my case I bought 24v panels because they were so cheap only to come here and find out that I had to spend 3x as much to use them. I found the Eco-worthy a year later but it is still twice as much as the panel it runs. Worth it, yes because the panels are worthless without MPPT.

Are these for your RV? I would say find out what panels FIT be they 12v or 24v and then work the rest out after.

i have a blue sky 2000e MPPT controller, it is possibly one of the oldest MPPT controllers around

set points can be adjusted by the POT's on the inside

36v panels and above is where you will really see the advantage MPPT where the output amps will be higher than the panel rating and the controller can maintain the bulk voltage set point

my low voltage panels don't allow for as much AMP gain above rating, as higher voltage panels, but the MPPT does mean the bulk voltage/peak voltage is maintained, even at low amps, so i get a better top off than PWM

my 2000e has a peak voltage rating that is NOT high enough to allow for series panels, if i ever change controllers, i will get either an 'Outback'
or
one of the new cheaper high voltage chineese controllers that have been posted in this forum

IF you get a 90v controller you series the 36v panels =72v
but the 50v mark 'for series panels' is Not attainable unless you go with lower voltage panels

my 505w of low voltage panels , Flat on my RV roof
collected 70.78 AHr , 957.5 watt hrs, Thursday, with a PEAK 14.47 AMPS / 195.1watts
this in smoggy calif, NOT QZ Az

Hi mex,

The cable from the panels to the controller need to be large, too, for mppt to work well.

In theory, 360 watts / battery voltage = input from the controller to the battery bank.

Losses on a 36 volt system at the controller may run as high as 5%.

The better the "smarts" in the controller the more energy will be harvested.

I have seen 17 amps from 256 watts on a system voltage of 33 input to the controller. The controller is a Blue Sky 3024di (so one generation out of date).

.I don't see 17 amps very often unless I run the inverter/

My proven method for calculating "expected amps" when pointed at a high sun, blue sky, with PWM is:

panel watts/130 x 8.2 = A

It has worked out right in real life using several different amounts, so it is fairly accurate, based on panels having an Isc proportional to a 130w with 8.2 Isc

So 360w should get you 360/130 x 8.2 = 23 amps. (note some mono panels have lower Isc per watt so they come out less, but most poly seems to be in the ball park)

Now what happens with MPPT? Most reports are that you get the same or a bit more, maybe 10% more tops. So your expected max amps with MPPT on 360w would be say 26 amps instead of 23.

Note there are some claims that the MPPT does better in the shoulder hours so you get extra AH per day than just comparing the expected max amps. No figures on that if true even. Say you get 15% more daily haul but just the 10% more max amps? No idea.

Note your controller whether MPPT or PWM should have an amps size 20% more than your expected max amps because there are times the solar does more amps than rated (edge of cloud effect is one) so for 26 amps expected, you should have a 30a controller. Some MPPT controllers clip the amps above their rating, so with them you can go to max, no 20% margin needed (eg Morningstar 15L ) With some PWMs they will let the amps through, but get too hot running above rated amps.

The other thing with controllers is their rated max voltage intake--total Voc of panels. One more volt than that for one second and you fry your controller! Yipes! So you need to figure the total Voc of your array when it is as cold out (when Voc is highest--not the rated Voc at 25C) as you will ever be camping and then allow some more margin besides to be safe.

In juggling panels and controller options you can have more than one controller, say if two smaller ones are cheaper than one big one. Same total amps on the battery.

One question you likely will get answers that are guesses is what MPPT controller is better than another. You will not find many that have actually purchased several to see which one is best. I bought ONE a Blue Sky Solar Boost 302? 40a controller and it works fine. Is it better or worse than others I have no idea. I have seen 42-43a at times and that is good enough for me.

Wow! you lost me on this question. I've not no idea what you're talking about! It must be something about solar panels, satellite systems, a new flush system, or some kind of new tow vehicle!