What about a Midnite large PWM only charge controller?
Something in the 80 to 120 amp range with 12,24,48 volt support.
Logic being that pvs are now so cheap that the need for mppt controllers will soon be best suited for limited PV space applications ie rvs, boats and homes with limited sun visible space.
In an area where space for pvs is not an issue then mppt offers doubtful advantage compared to simply adding more pvs and use a simpler and lower cost PWM type controller.
Perhaps time for Midnite to resurrect a more up to date version of the late 90s Heliotrope CC120 controller.
I can see it now, in the existing Classic case with simplified MNGP.
Dgd
Hey DGD, I see what you want and agree that , especially in warm climates that is a reasonable option, but up here in the Frozen North.... MPPT shines in winter compared to PWM.
Another caveat is you would have to be running true 12 or 24V panels (48?) ;)
Wb,
I think there will always be a place for decent mppt controllers but right now only Morningstar (apart from a sleuth of Chinese/Taiwanese offerings) provide any half decent PWM controllers although at 60amps thats a bit limited. They also lack any online stats/reporting capability apart from a fairly limited use small lcd display.
Have been thinking for some time about building a PWM controller in the 120 amp range, using a control arm processor to give it some nice reporting and setup features. A PWM algorithmn looks fairly straightforward to implement.
Be nice to have it work in cooperative mode with a Classic for charge stage alignment and also to have some auxiliary power output capability for other loads such as water heating etc..
Anyway, would be good if MN had such as offering but its more likely a project for me in the queue just behind the Oztules 6Kw 48v sine wave inverter I have just started with :D
Be nice to make use of those decent looking FETS and associated heatsinks left over from the InspireSolar GTI de-construction :P
dgd
Back on 2000, bob was actually workong on a large bang bang charge controller that would have used a mercury displacement relay i read on some forum that rv power products daod they could not make a more powerful mppt. On that day, bob started on the outback mx60. My goal since then has been to rid the world of pwm contrpllers
After mario completes his three controller designs now on his plate we can look at tjis possibility
I am answering things on the forum this morning because i locked the leys on my car at the car wash and am now waiting for bob to come bail me out.
Funny Robin !
Be Safe
Quote from: Robin on January 30, 2016, 12:27:08 PM
After mario completes his three controller designs now on his plate we can look at tjis possibility
I assume one of them is the big KID that was talked about some time ago?
I was thinking about an 80 to 200amp PWM controller. Mainly because the cost of PVs has dropped so much. Maybe stackable or slaved to smarter device such as Classic next gen.
One Classic or Kid working mppt with its own PV array then charge state control being passed to networked PWM controller(s) on separate arrays. Perhaps the processor in the mppt controller managing diversion of power from PWM controller to other purpose, charging EV (vehicle, bicycle etc), hot water, heating, fuel cell etc..
dgd
I am still hopefull tp get down to auckland soon. If that happens you can twist my a about pwm. I dont see much of a market for it but i could be wrong.
pwm has their place, but it is beating a dead horse. the only way it would probably make sense for midnite to do it is if they break the price barriers on these basic regulators.
Robin, did you ever get your car out of hock at the car wash ?
Quote from: Robin on May 07, 2016, 04:31:30 PM
I am still hopefull tp get down to auckland soon. If that happens you can twist my a about pwm. I dont see much of a market for it but i could be wrong.
oops, missed this post.. If you do plan an Auckland visit, perhaps your Winter when it will be Summer here then would enjoy meeting you and if you had time could visit a couple of local small RE homes using Classic and other MN stuff
dgd
Power conversion is no longer the frontier; it is power storage. I would love to see the best minds at Midnite engaged in some sort of photosynthesis project If we could store PV power in synthetic carbohydrates such as alcohol or gasoline, then today's best batteries, such as those prospected to be made in Tesla battery factory in Nevada, could be beaten. I see a huge opportunity in this space and plenty of capital thanks to Bill Gates foundation.
Also PWM charge regs can be RF quiet, increasing slew rate of switching
All of the larger sized solar modules I've seen (200+ watts) all output over 30 volts. How will a PWM only CC feed that to a 12 volt, or even a 24 volt battery bank? One of the best features of MPPT is its ability to take high voltages and feed 12 and 24 volt banks. It only gets harder if the modules are wired in series, my solar array feeds 100+ volts into the CC. Isn't that what the Classic model numbers mean, 150, 200, and 250 volt input maximums. How will a PWM only feed those voltages to a 12 or 24 or even 48 volt battery bank?
Looking to learn...
You have just hit on the problem. PWM charges require 12V solar panels. Those are not so cheap.
I completely agree with dgd, about the need for a high output PWM CC, with good communication abilities, and battery Sense Terminals.
In the past year, or so, there are a number of PV manufacturers that have returned to making high power 72-Cell PVs. For 24 V and 48 V systems these 72 cell PVs are perfect.
Here is an example:
http://www.solar-electric.com/solarworld-sunmodule-sw-315-monocrystalline-solar-panel.html
FWIW, Vic
Yeah im in too. With 72 cell panels and 24 or 48V systems, short cables, youre right on the MPP most of the time.
The thing about MPPT is that it works with any old panels. But you design your system once, and after that the MPPT lives within a very tight band, which basically wastes the controller.
As far as MPPT goes I think to be honest a lot of trouble could be saved by simply telling the controller what the array Vmp is, and let it hang out there.
But I accept that marketing bling will probably prevail.
Quote from: zoneblue on July 25, 2016, 09:25:23 PM
The thing about MPPT is that it works with any old panels. But you design your system once, and after that the MPPT lives within a very tight band, which basically wastes the controller.
As far as MPPT goes I think to be honest a lot of trouble could be saved by simply telling the controller what the array Vmp is, and let it hang out there.
With many designs it's so easy (cheap) to over panel that the need to often seek the mpp is unnecessary and in doing so (sweeping) actually reduces overall power input hence efficiency.
Since mppt is only effective during bulk then the voltage limiting charge stages make the controller just a DC to DC converter with PWM current limiting then maybe that's what the design of a new simplified controller should be.
Maybe there could be some argument for a voltage converter front end, Buck and Boost, for the long cable runs or use of cheaper 60 cell PVs, but since 36/72 cell PVs are still cheap I would vote for a simple design but decent 120 to 200 amp output range
Of course the need for a decent Cpu is still there and I'd still include WBjr/shunt for charge current control, a decent number of basic aux controls including
force float for multi controller use, a direct battery connected voltage sensing, and some reasonable web reporting of running data as well as logging.
Enet and serial ports would be good and maintaining modbus registers (can't believe I suggested that!)
Dgd