Solar Panel Selection

Re: Solar Panel Selection

Kent,

Your PV array specs for your “48 V” system will be narrowly bracketed at the low end by a minimum operating voltage requirement and hot temperature, and at the high end by equipment input voltage limits and cold temperatures.

The combination of high ambient temperature and losses in the array wiring and the charge controller could result in a voltage level of about 75% of array STC Vmp spec being delivered to the battery bank. If you need 62 V to charge and EQ the 48 V bank, the array’s STC Vmp spec should be ~62 V / 75% = ~83 V.

Low ambient temperature early on a winter morning in your neck of the woods (-5F to -40 F range?) could cause the array’s Voc to increase by ~25%. The MX60’s operational limit is ~140 VDC, so you’ll likely need to build an array rated at 140 Voc /125% = 112 Voc STC.

The challenge now is to build an array for between $6K and $7K, rated at between 1,200 W STC and 1,440 W STC, and with array voltages of >/= 83 Vmp </= 112 Voc.

One option is an array of ten Kyocera KC-130’s wired in a 5 (in series) x 2 (in parallel) array and rated at 1,300 W STC. With STC module specs of 17.6 Vmp and 21.9 Voc, the array’s STC voltages would be 17.6 Vmp/module x 5 modules = 88 Vmp, and 21.9 Voc/module x 5 modules = 109.5 Voc.

At $2,390/four modules, ten should cost ~$6K (plus shipping). This configuration meets your goals for price and power, and it meets the electrical spec limits described above. A 1,300 W array should also be a comfortable match for your 48 V x 210 Ah battery bank. Perfect!

I skipped the associated current calculations, because, as you probably know, the MX60 can easily handle a 1,200 W STC – 1,440 W STC PV array when operating in a 48 V system. In terms of scalability, the controller could comfortable handle at least 20 of these modules (2,600 W STC) in five-module increments, and perhaps even 25 (3,250 W STC), should you decide to expand your system at a later date.

HTH,
Jim / crewzer