Peak Power on a perfect day

Re: Peak Power on a perfect day

That depends, some installers compute wire size for up to 3% loss between panels & inverter, the max efficency of the inverter is listed as 97.1%. So, 7560 * .97 = 7333.2 watts * .971 = 7120 watts. March is not the best month to look for max output... sun is still to low, cooler temps help. if you refegerate the panels to say 40degrees in june you may get 7560..

Note: the California solar website rates the REC210AE-US 210W as having a output of 182.7 watts. If they are correct then you have a 6577 watt aray.

6500 watts from a 6577 array ain't bad!

Re: Peak Power on a perfect day

6500W is pretty good for February.

What's your orientation?

I bet you will get over 7560W on some sunny but not too hot day.

Re: Peak Power on a perfect day

MX60 watts display = Make believe watts , usually 5-10% above actual, I've tested over 6 different units over the years, they all error on the optimistic side. Every single time I see a post about so magic array harvest values, its always an Outback charger that is what reported the values. Does make for some very happy customers though:roll:

Re: Peak Power on a perfect day

I have a Flex Max 80 here and its also reading over actual panel input and actual output to battery.

If only MorningStar had a 80A MPPT Controller.

Re: Peak Power on a perfect day

RWB wrote: »

I have a Flex Max 80 here and its also reading over actual panel input and actual output to battery.

If only MorningStar had a 80A MPPT Controller.

i would think the outback meters could be recalibrated somehow. even if you could do it you need something to calibrate against or you would be guessing. why not ask outback to resolve the accuracy of the meter?

Re: Peak Power on a perfect day

niel wrote: »

i would think the outback meters could be recalibrated somehow. even if you could do it you need something to calibrate against or you would be guessing. why not ask outback to resolve the accuracy of the meter?

The half-dozen or so OutBacks I see on a regular basis where the charge controller output passes through its own shunts on an FN-DC are within 20 or 30 watts. During some recent high output days here I was seeing that same 20 or 30 watts that I've seen on lower output days, which tells me that they are reporting power before whatever the charge controller is consuming.

And before anyone questions the FN-DC, I routinely calibrate FN-DCs with a Fluke 289 (which is not a cheap Chinese DMM) and I've yet to find one that isn't within +/- 0.1 amp under load.

Re: Peak Power on a perfect day

All the more reason for a god battery monitor to see just what is going in to the battery ( and out at night)

EJ

Re: Peak Power on a perfect day

tallgirl wrote: »

We're closer to the Sun right now than in the Summer. The day of closest approach is around January 3rd. The difference is 6% more solar radiation to the ground compared to the low which happens in July or so. After I corrected my software for orbital geometry the 10 to 15 percent over nameplate values I'd been seeing dropped by a couple of percentage points.

Ok so to make sure I get what your saying right let me confirm this with you:

January 3rd is the Earth is Closest to the Sun and this generates 6% more Solar Radiation to the ground/solar panels which can be turned into electricity.

So your saying that its not fair to compare your panels output on January 3rd to its output in July because the panel is actually getting 6% Less Solar Radiation in July than in January. You have to factor in the 6% Radiation Increase when your comparing the 2 different readings. Interesting indeed.

One question I have is this: Assuming that the panel is fixed at the correct tilt for its location and the sun is at 1000wm, what time of year would give you max solar radiation that PV's are looking for? What time of year should you see max wattage output assuming the temp was always 70F.

I think I'm asking that right. Maybe its more complicated than that.

tallgirl - The half-dozen or so OutBacks I see on a regular basis where the charge controller output passes through its own shunts on an FN-DC are within 20 or 30 watts. During some recent high output days here I was seeing that same 20 or 30 watts that I've seen on lower output days, which tells me that they are reporting power before whatever the charge controller is consuming.

And before anyone questions the FN-DC, I routinely calibrate FN-DCs with a Fluke 289 (which is not a cheap Chinese DMM) and I've yet to find one that isn't within +/- 0.1 amp under load.

I have seen up to 1Amp difference between the FM out to battery reading vs what the WattsUp meter was actually reading being put out the battery. Sometimes the output and actual output was very close and alot of times it was off by .2-.5 amps, which bothers me for the simple fact that I can not rely on the actual readings of the FM80 for daily solar totals or current Watt Hour Totals.

So TallGirl you think its just because the reading does not take into account for the losses created during the DC to DC Conversion Process of the MPPT? If that's the case then its good to know what is actually going on with the machine.

Does Morning Star have the same issue with their new MPPT 45 and 60? If not why can't Outback do this on this Flex Max series? Its one of the only complaints with the device so far. The voltage reading during Night time is the 2nd complaint I have with it.

Bob - The input current reading of the MX/MF will read especially high because it is a calculated number from the output current and voltage and input voltage.
The problem is that it does not take converter efficiency into account, which ~could~ be done but is not easy to do well.

So you know for a fact that this is what is going on Bob? if so then Thanks for explaining exactly why this happens. Basicaly its doing a math problem and displaying the answer vs reading actual DC output via a Shunt?

Re: Peak Power on a perfect day

tallgirl wrote: »

We're closer to the Sun right now than in the Summer. The day of closest approach is around January 3rd. The difference is 6% more solar radiation to the ground compared to the low which happens in July or so. ...

As RWB said later, this is interesting and helpful to know. I didn't know this either. Thank you.

What I've learned is that insolation for a cloudless day is not just a function of the number of sunlight hours for a given day; it's also a function of a 2nd variable, that is how far away the sun is to the earth.

Looks to me that the only way (in the field) to affirm solar panel harvest for a given day is to first know an accurate insolation number for the day. And that this will require an accurate solar radiation meter with ability to integrate the readings into an insolation number.

Many thanks.

Best regards,

Bill

Re: Peak Power on a perfect day

PV watts is the best overall "setter upper" - you can play with angles all day, and only waste a few sheets of paper !

For portable panels, I set mine to minimize the shadow it casts. that ALWAYS places it perpendicular to the sun (for 10 minutes) so I'll pre-aim it, and get a couple hours of non-attended, near peak power.
http://www.mike-burgess.org/images/Mono_2005_CS_056.JPG

No meter needed.

Re: Peak Power on a perfect day

Thanks for the awesome links guys!

I'm digging the affordable meters............

I'm learning something new everyday LOL