a check on my results

nyarelathodep

So I was hoping to get a little feedback on how my system is operating thus far, see if anything could be tweaked, if the numbers seem fairly normal. ..

Location: Western Maine, lat:44.39, lon:-70.43
Panels: pair of 250w Canadian solar in series to a C150
Panel orientation: 187° S, 47.5° inclination.
So far, the best day I've seen (bout 4 days ago) was 1.1kw, a peak charge of 19a, topped out at 520watts. Most days are in the 0.3-.0.6 kw range...oppressive opaque cloudy haze more often than not. My peak charge hours seem to be 11:30-12:30.
So are these numbers pretty typical for one to expect this time of year up here? Any critique on the panel orientation? I built the frame myself from pressure treated lumber and have allowed to raise and lower the incline to almost any angle.

BB.

Re: a check on my results

What voltage is the 19 Amps at?

520 watts / 19 amps = 27.4 volts

I am guessing that is your battery bank charging voltage?

If so, that would seem to indicate a relatively discharged battery bank (equivalent to ~13.7 volts for a 12 volt bank). Very cold weather and possibly well above sea level elevation?

But, given that you have been having "issues" with lack of sun this time of year--Understandable.

Overall, seems to be doing very well. Warm summer days, a little dust on the array, and a little age--You would be looking at something like:

500 watts * 0.77 (panel+controller derating) = 385 Watts "typical" maximum output power to battery bank

The 1.1 kW output--Not sure what you mean by that... It would be very rare for an array to produce 2x its rated output unless you have an "edge of cloud effect" (sort term--seconds to minutes usually) or reflections from a snow field out in front of the array.

Also--In general, the accuracy of charge controllers is not that great--Typically they run 0% to 5% high (indicate more wattage than actually generated), and can be as much as +/- 10% from "true" numbers. So, when your system is running pretty close to nominal or better--Just enjoy the power and don't turn it into a numbers game.

-Bill

nyarelathodep

Re: a check on my results

The incoming voltage, as read on the cc, was about 67v, the battery voltage read 27. These batteries are brand new (barely a week old) 4 t105re's (24 v). When i say 1.1kw, that was the total days harvest on the best day... Cold (avg single digits, though today is 50ish), completely cloudless full sun on that particular day.

nyarelathodep

Re: a check on my results

All the charge parameters were the recommend values for those batteries. I can't imagine a depleted bank... We never draw even 3 amps continuous... usually half that under most circumstances.

BB.

Re: a check on my results

OK, that would be 1.1 kWatt*Hours per day.... or 1.1 kWH per day

1,100 WH per day / ~500 watts full sun = 2.2 hours of equivalent noon time sun per day.

If you assume typical derating:

1,100 WH per day / (500 Watts * 0.77 derating) = 2.9 Hours of Sun per day

Using PV Watts for Caribou Maine:



Month
Solar Radiation
(kWh/m²/day)


1
3.36


2
4.34


3
5.23


4
5.75



5
4.99


6
5.09


7
5.15


8
4.99


9
4.26


10
3.45


11
2.38


12
2.73


Year
4.31



Sort of in-line with the predicted amount of sun... However, remember that for an off grid power system... That represents the power harvested to refill the battery bank and run your loads. So, assuming the system fills the battery by afternoon, then it would be cutting back on harvest on those days (more sun than power you have consumed).

-Bill

nyarelathodep

Re: a check on my results

That's more or less good to hear. Typically, during the day i shut the inverter right off and no loads are being drawn. I'm not sure what constitutes a full battery, but I've seen a high of 96%, and mostly I'm bopping between 75% and 85%. It might be a silly question, but do i want to see that bank as close to 100% as often as possible? My next step is another 2 Panels at any rate, facing slightly more to the west. I believe that will generate a charge rate of maybe 14%.

BB.

Re: a check on my results

No, it is open to argument, but over 90% once or twice a week should be fine with a daily cycling battery bank.

As measured with a hydrometer. You can use the battery monitor once you have validated it's configuration. Battery monitors can mislead too.

-Bill