It will generate MORE power using the MX60 with the mppt than adding 2 panels without mppt.

It really makes little sense on any moderate to large systems NOT to have an mppt controller , the loss is power is just to great.

Now with the odd voltage panels , it's even harder to try and match to a battery float voltage.

I beleive the MX60 is about 480.00 , not much more than a single 120 watt panel

Thanks for all the posts on the subject! I continue to learn a great deal by reading all of the posts in all of the sections. Thanks again for the vehicle to do this Solar Guppy!

I received my MX60 last week finally and got it installed over the weekend. It's been stormy and rediculously cloudy here the past few days and so far the MX60 is GOLD! I have to admit I was sceptical of this little black box. For a very brief time when various layers of clouds were passing over I got 2200 Watts out of the system on a cloudy day accoring to the MX60. I was monitoring the amps on the AC side and measured 18 amps! Even when it's really dark and cloudy/rainy, the system is producing about 3 to 5 amps (AC) whereas before the MPPT I was getting 1 or 2 amps (AC). I'm amazed at the "cloudy" performance. I have yet to see it run when it is sunny, but now I have little doubt it will perform well.

I have been thinking about rewiring the system to 5 sets of three arrays, but doubt I will now with the performance I'm getting so far. After seeing a couple of days with the MX60 I would certainly agree that the system will produce more power with it than without it -even if I bought the two additional panels.

Regarding wiring the panels in 5 sets of three... (I can sell the one extra panel back.) does anyone think it would be worth the trouble now that I have the MX60? Any evidence supporting the argument either way? By doing the sets of three instead of the existing four, would the MX60 do even a better job? My personal feelings are I'd be doing a lot of work for little to no performance gain at this point. FYI, I have noticed that the panels like to sit about 20.5V under load (82-83V).

I understand the basic principal of the MX60, but anything more than that, it's pure magic to me! I need to learn more about how MPPT works...

Finally, for the record I do have the battery temp probes for both the MPPT and the 4048.

Thanks again to everyone for all of the feedback.

Anthony

No , rewiring to 5 panels in a string won't gain you anything ... though you'll have slightly less losses in the wiring this will be offset by the lower effientcy of the MX60 running at the higher voltages.

Let us know how full sun works !

Well, I'm afraid I might have mistyped and confused. While I still don't think it will make enough difference, what I was trying to say is rewiring the panels to where there are 5 arrays of three panels each instead of the four sets of four I now have. This way the voltage of the panels will be a little lower to begin with and closer to the battery voltage. My cursory thinking is the voltage will be less mismatched. This is what the MX60 is for I know. My apologies for the confusion.

Cool sunny days yield right at 2000 watts! Now this is the amount of power I was expecting. I am a little curious as to why the power peaks at 2200+ when the sun peeks out in between cloud cover? Is this the nature of the panels or the MX60 or both? I've seen this happen several times on partly cloudy days at temps from 50 to 80 degrees. Just curious...

Thanks!

Anthony

Hi Anthony,

That is caused by what is known as "edge of cloud effect". Apparently there is a focusing effect at the edge of clouds which causes more light to fall on your solar panels. The result of more light is more current!

This effect is one of the reasons there is such a healthy multiplier (derating) for current required by the NEC for your PV wiring.

Like you, this was something about which I was completely unaware until I installed a PV system (and asked about on the internet).

Enjoy your new system!

George

The MX60 can't boost the voltage , so using 3 panels per string vs 4 isn't a good idea.

What can happen is in hot weather , the true mppt point could be BELOW the battery charge point. This is the only real knock on mppt controllers (added cost but in hot weather , not added performance).

You , by chance are doing EXACTLY what is necessary to get the mppt advantage ALL the time , by adding another panel to your string , the mppt point is always above the charge value for a 48 volt battery bank , so no need to change , you have it right as it is !!

Thanks for the responses! I forgot about the MPPT possibly being below the batteries.

The "edge of cloud effect" is something I would have never believed or figured out. Thanks again for the valuable info.

Anthony

heres something i was reading off the xantrex site, about using pfc caps to correct the inverter output
http://www.xantrex.com/web/id/344/DocServe.aspx

also this
http://www.xantrex.com/web/id/343/DocServe.aspx
if i understand this right,the inverter output at the meter may not be correct due to a power correction factor due to inductive and reactive loads.
i hope this helps