Hi BFL13,
It has nothing to do with clever. It has to do with cost effective.
My first RV had 30 watts of solar on it. Installed cost was $1200.00. Price per watt was $40.00.
My existing solar system has panels that are now 10 years old (when purchased). They were $1700 for parts and $600 for labor for 256 watts. At those price levels MPPT makes good sense. Installed cost per watt would be $8.98.
Now, panels are as low as $0.69 cents per watt. Installation would remain about the same at $600 for four panels--but the cost of the controller could be as low as $30 (or $100 for mppt) and the panels themselves would only be ~$180.00. So my system would now have an installed cost of $880.00. Cost per watt is only $3.43 (including the elcheapo MPPT). The savings on pwm are $70.00.
BTW for those who don't know, my system voltage coming into the controller is 33 volts. I'd have to have way more than 51 C beating down on them to reduce the output to the point where I could not charge.
If I were to redo today I would definitely consider pwm. But then I want to get to 1500 watts, for I've seen my air conditioner with nada else running go up from 1200 to 1900 watts. It may be that MPPT would end up being cheaper, because the high voltage panels are less expensive. I'll have to work out the price--and I'll use what ever is cheaper.
My system was designed to maintain the battery bank between trips. I'm now full time in it, so it no longer meets my (ravenous) needs. 1/2 my battery bank is nine years old and the capacity I once had is no longer there. It may be that the solar will have to wait on the battery bank replacement. I save enough for one major upgrade per year, and with eight batteries (7 for house) to purchase it won't be cheap.
