Usefulness Of MPPT Technology
This isn't a trick question. I wish to take a "Short Course" in the reality versus hype of MPPT control... Users who have MPPT and can report real-life experience... Let's say I get a pair of panel...
Forum Discussion
My might-be-out-of-whack thinking is to take advantage of the most watts per dollar damn-the-torpedoes bigger won't hurt a thing. If I could find 4' X 8' panels I could use them, regardless of voltage but obviously (?) Four, say 38 volt panels would be great, in series parallel configuration. I would like to end up with 30-40 amperes potential @ 28.0 volts. They are intended to be mounted on the roof of my "umbilical logistics support" structure alongside my R.V. I am going to "try" and squeeze out several hours of 430 watt 5,000 BTU window air conditioning out of my 2-volt cells. This sounds wacky until a person realizes power down here costs barely 5 cents per kWh. For a very limited total per billing cycle. Once a person goes into DAC (Data Alto Consumo) the entire bill every last kWh zooms to fifty cents a kilowatt hour. Yes, that means two George Washington quarters every single kWh. And it stays in DAC for half a year. Half a kilowatt every hour for five hours a night, times a 60 day billing cycle. 2-1/2 times 60 = 150kWh. That magic 150 puts me into DAC. 150 kWh PLUS the difference of the other 350 kWh I consume compared between basic and DAC means many hundreds of dollars EXTRA every 60 days. Doesn't take long before panel AC becomes attractive. I have a Trace 4024 inverter and 1,650 amp hours @ 24V worth of batteries. And some 19.0 voc Kyocera panels. I'll keep the Kyoceras for 12 volt LED illumination for emergency lighting.
Basically, with the average 11.5 - 12.5 hours of usable daylight we have down here (18 degrees latitude), I figure I'll get 7.5 hours of usable >90% potential charging from flat mounted panels. That pencils out to be a comfortable margin to take care of inverter and battery losses. The roof of the structure can accept 12' wide by 30' worth of panels. My wallet is the limitation.
The dirt cheapest generator usage consumes 1.5 gallons every 5 hours. Three and a half dollars a gallon. Five bucks for 5 hours of AC use. Plus hauling and storing gas and replacing stuff that wears out.
Basically, with the average 11.5 - 12.5 hours of usable daylight we have down here (18 degrees latitude), I figure I'll get 7.5 hours of usable >90% potential charging from flat mounted panels. That pencils out to be a comfortable margin to take care of inverter and battery losses. The roof of the structure can accept 12' wide by 30' worth of panels. My wallet is the limitation.
The dirt cheapest generator usage consumes 1.5 gallons every 5 hours. Three and a half dollars a gallon. Five bucks for 5 hours of AC use. Plus hauling and storing gas and replacing stuff that wears out.
