Reliable Charge Controller, Inverter

Re: Reliable Charge Controller, Inverter

Considering your proposed system size and location, I’d suggest the following:

1)  Charge controller. Factoring in generally warm ambient conditions and overall array size, I don’t think that an MPPT controller will be of any great benefit to you. Accordingly, I recommend a Morningstar Tristar 60 with its optional digital meter and remote battery temp sensor. Considering that typical mid-day bulk stage charge current from your “24 V” array will be  1,000 W STC x 85% / 28 V = ~30 A, the 60 shouldn’t ever be stressed. You might want to consider also buying a TriStar 45 as a backup (same physicall size and connections, and the optional meter and RTS can be switched over). Both TriStar controllers plus the meter and RTS will cost less than an OutBack MX60 controller alone.

http://www.morningstarcorp.com/products/TriStar/info/TS_DataSheet.pdf
http://www.morningstarcorp.com/products/TriStar/info/TS_Manual.pdf
http://store.solar-electric.com/mochco.html

2)  Inverter. I agree that the Exeltech XP true sine-wave (TSW) inverters are definitely worth considering. Do not even begin to consider a modified sine-wave (MSW) inverter. Exeltech's MTBF claims are impressive, and they appear to be conservatively rated. For example, their power output specs are in real Watts (Volts x Amps x power factor, and not just Volts x Amps), and their full-power temperature spec is 30 C (86 F) as opposed to the usual 25 C (77 F). Inverter efficiency is important as well, as higher efficiency means less waste heat and longer operating time for your loads.

http://www.exeltech.com/ex_root/ex_products/ex_inverters/ex_xp/ex_xp_specs.htm
http://www.exeltech.com/ex_root/ex_literature/931-X61M%7E-%7E0C%20web%208%205%20x%2011.pdf
http://store.solar-electric.com/exsiwain.html

The OutBack FX2524T inverter (2500 VA, 24 VDC in) might be another candidate. It's a very rugged and high quality TSW inverter, and it includes a batetry charger that might be helpful for charging your batteries from a generator during a prolonged stretch of bad weather and/or heavy loads. It's not cheap, but no good inverter is, and, in addition to the battery charger, it's rated at 2,500 VA.

http://www.outbackpower.com/OffGrid.htm
http://store.solar-electric.com/fx2524t.html

3)  Finally, your location’s warm ambient temperatures will reduce the power output from your PV array. Specifically, you may see output power that’s ~85% of the nameplate rating, and essentially all of this loss will manifest itself as reduced array output voltage. Accordingly, you’ll want to specify 12 V PV modules with an STC Vmp spec of at least 17.0 V. Personally, I’d shoot for something in the >/= 17.3 V range. If you’ll looking at “24 V” PV modules, you’ll want to double those numbers.

You'll also need a safe and reliable way to electrically integrate the PV array, the controller, the inverter and the battery bank. Something like the E-Panel Lite (for the Exeltech inverter) or a regular E-Panel (for the OutBack inverter) from Midnite Solar might get you started in the right direction. See: http://www.midnitesolar.com/MidNite-Products.html

HTH, and good luck!
Jim / crewzer