Lowest OCV An MPPT Is "Worth It"?
There has to be some experience here on this forum to share. When I look at the MPPT manufacturer's data specs, the incredo-hyperbole gives me diarrhea.
Forum Discussion
MEXICOWANDERER wrote:
400 watts at 17.5 volts? I am trying to clarify my question :)
So 400 watts at 17.5V is about 23 amps. Realistically, you'll need something like panels that will claim perhaps more amps at 17.0 or 17.1 V, if you decide to go with PWM. Although my 120W panel puts out about 7.0 amps, by the time it goes through my PWM device and gets adjusted to what ever voltage I decide, the end results is I only get 6.67 Amps, regardless of peak set voltage for bulk charging.
I don't know if the amp loss is proportional to the output in amps of the panels, or if it's a flat .3 Amp lost regardless of if it's 15 amps, 20 amps or a 30 amp controller.
As has been said many times before, when you're looking at PWM, you are looking at Amp output, and a slight loss from panel ratings once through the charge controller. I too bought the Solar 30 for $34. Plenty for 400 watts. Voltage programmable. How many amps at what voltage do you need to charge your battery banks based on estimated usage and SOC in the morning when the sun comes up?
At 400 watts, with a 30 amp PWM handling the chores... and you can get 2.3 amps more, times hours per day, with MPPT... are you setting and forgetting the panels, not aiming them, not chasing the sun?
Too many variables... On a budget... PWM... if you are designing it for Big Daddy WarBucks... and it's cost plus.... MPPT.
Solar Blvd sent me a Black Friday special with 100 watt 21.8V panels for $95 each, and 120 watt panels, same voltage, for $115 each.
At under a dollar a watt, you can replace 2 amps lost without MPPT and using PWM, if your system uses under 30 amps, for under $30 with just more or larger panels. $30 vs $300 for MPPT... and the price per watt keeps on dropping.... your bell shape is moving, constantly, due to variables.
