OSU Solar Trailer charging a TeslaSnapshot of Outback Inverters and other system componentsThis utility trailer was initially designed by OSU students as a senior project in mechanical engineering. It was constructed in 2007 to educate about photovoltaic (solar electric) energy and provide a renewable, portable power supply. It has been used to provide electricity to campus and community events at remote locations where power was otherwise unavailable. 

A few years later, some of the lead acid batteries failed and were removed, reducing the pack to three sub-packs of four 12V batteries. Still configured in a 48V system. This reduced pack weighed 1926lbs and was rated to produce 771Ah at 48V (37kW/hr), if it was new that is. It was rated to provide 250 cycles if discharged to 75% on each cycle. The heavy and aged battery pack performance was estimated at 29.5kW/hr at best. 

SHIFT EV was contracted to replace the lead batteries with Lithium. This included some system and structural design work, assembly, cabling, wiring and integration of the BMS with the inverter/charging system. We installed 48 180Ah LiFePO4 cells (593 lbs), rated to produce 29.2kW/hr. If you caught the math error, it's no error. The 180 case sized cells selected are now rated for >190Ah by the manufacturer. Cycle life of the new cells is rated for 2000 cycles (@ 80% DOD).

One of two Li packs, with Manzanita digital reg

Touch screen interface displays a bar for each monitored cell (3P in this case)The Battery Management System (BMS) we installed is a digitaly networked system from Manzanita Micro, with the touch screen interface co-developed with BSD. 

Other specifications:

  • 1800 watt solar array - nine Sanyo 200 watt solar modules
  • Two 3.6 kilowatt Outback grid interactive inverters, capable of 7.2 kW (60 Amps @ 120 Volt or 30 Amps @ 240 Volt)
  • Original batteries: 16 MK 12 volt deep cycle absorbed glass matt batteries, each weighing 158 lbs. for a total battery weight of 2528 lbs.
  • Two 20 amp 120 volt circuits feeding 4 standard 120V household outlets
  • One 30 amp 240 volt circuit powering one dryer style outlet
  • Wattsun dual axis sun tracker system
  • Expandable, fold out array
  • Mechanical lift moves array into sun tracking position