Roll Up Solar Panels / Ogre MPPT Controller

pnichols wrote:

BFL13 wrote:
I don't know why you want mono and MPPT for a small solar set.

Other than me figuring out how to budget for it, what's the downside to mono panels feeding a MPPT controller?

I thought a MPPT controller effectively gained you 20-30% more amp hours per day from a given panel area? Which if so, means you buy 20-30% less panels and have a 20-30% smaller sized portable panel setup to find storage room for. IAW, 100 watts of mono and MPPT will provide what it takes 120-130 watts of poly and PWM to equal.

I am shocked, just shocked, that you haven't been reading all these solar threads over the last few years!

The advertised 20-30% gains with MPPT vs PWM are taken very early and late in the day, not at the mid-day hours of most solar intake, when the MPPT is more like 10% better. IE, 1 amp more than 2 amps is 50% gain. but 1 amp more than 10 amps is 10% gain.

Beware of salesmen :)

BUT, that is only when the panels are cooler as in winter. When the panels are at 50C, they lose 10% of their power.

So I find that in summer here at 25C the panels are 51C and my amps are way down from "expected." Comparable numbers for noon amps:
MPPT/PWM

April 15.5a/14.5a
July 13.5a/14.5a

So where and when will you be using the solar? Anywhere it is near 25C ambient and sunny, you will get more from PWM based on my experience with both.

Is the 15.5 vs 14.5a worth any money? Compare the cost of the MPPT vs the PWM to get that extra amp. (which is not 20-30% either :) )

So with the amps and thus AH being a wash overall. that leaves roof real estate, maybe wiring gauge (wiring a fairly trivial factor IMO), and cost as the factors. Cost is confusing with all the sales and prices with and without shipping thrown in--you have to grab whatever deal is on when you are needing the solar.

Mono vs poly seems to be mostly about the monos having higher voltage but lower amps than poly, which works better for MPPT but worse for PWM. There is also some reporting of lower output in low light with mono than with poly by JiminDenver who has both.

Taken all together, it favours poly and PWM for a small set-up.

Also if talking portable set-ups two 12s is easier to man-handle than one big 24. So now your choice is series with the 12s and MPPT or parallel with PWM but putting 12s in series jacks up the voltage past the intake limit of the lowest cost MPPT controller, forcing you to get an expensive one. This must be compared with the cost of the PWM controller and the more expensive 12s compared with the cheaper 24s per watt.


Takes a bit of figuring and an eye on the sales while avoiding shipping costs.