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Power Electronics • Battery • Charging System • Supplying Power to Ink Choosing the Battery • Battery Type has to first be chosen “Batteries and Charge Control for Stand-Alone Photovoltaic Systems : Fundamentals and Applications” , James P. Dunlop Battery Capacity • • • • • • • • How much energy is stored in the battery measured in ampere hours Ah will provide ‘X’ amps of current for ‘Y’ hrs Ah = Device Wattage (W) * Time to run (hrs)/ Battery Voltage (V) From previous calculation we assume the total amount of power that we can use is 29,000 Wh/m2 , are prototype is 3’x5’ (0.92m x 1.525m) Therefore the total power used in a year can be about 40,600Wh Assuming snowfall for 240hrs a year (59 days for 4hrs) the average amount of power of the device will be 170W (40,600Wh/240h) Therefore Ah = (170W*4h)/ 12V = 56Ah To increase battery performance and life the battery should not be consistently discharged below 60% capacity so to be safe the battery capacity should be about 90aH Battery Options • Trojan Deep-Cycle AGM Battery can be used • 31-AGM could all be options with 5hr ratecapacity of 82Ah • Can be purchased from civicsolar for $270 Battery Chargers • Controls incoming charge of the battery • AGM batteries are INTOLERANT to overcharge • Standard Solar Chargers or MPPT (Maximum power point tracking) charger • MPPT chargers are much more efficient • Standard chargers can lose between 20-60% of the rated solar panel wattage Choosing a Battery Charger • Charger needs to be able to handle rated watt, voltage, and current rating of PV panel (charging source) • Charging source is still being determined (Full Panel or select number of cells) • For now we can base the charger chose off a SBM solar 150W panel with the following specs: Possible MPPT Charge Controller • Morningstar SunSaver 15 Amp MPPT Solar Charge Controller ($225) Power used from possible 150W: Power= PV Panel Power * Efficiency Power = 150W * 97.5% Power=146.25 Charge Current = Power/Battery Voltage Charge Current = 146.25W/12V Charge Current =12.2A Charging Time = Battery Ah / Charge Current = 100Ah/ (12.2A) Charging Time = 8.2 hrs Possible Standard Charge Controller • Morningstar SS-20L 20 Amp PWM Solar Charge Controllers w/LVD ($78) Power used from possible 150W: Power = Voltage *Charge Current Power = 12V *8A Power = 96W about 66% efficient Charging Time = Battery Ah / Charge Current = 100Ah/ (8A) Charging Time = 12.5 hrs Ink Power Supply Rtrace1 RTotal Rtrace2 Battery Regulating Circuit Rtrace3 I out Rtrace4 ( Power Needed to Heat Ink) Iout RTotal