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Large Charge Controllers
Larger solar power systems require advanced charge regulation. The Morninstar TriStar series offers a very high capacity and lots of features for the dollar. For increased charging amps in heavily used systems in locations experiencing cold temperatures OutBack, Midnite, Blue Sky, and Morningstar offer high capacity maximum power point tracking (MPPT) units. Solar arrays that need the voltage stepped down require an MPPT controller. The larger MPPT controllers also offers extreme flexibility in input voltage and will handle 60-90 amps into a 12, 24, 36, 48V, or 72V battery. Note the power ratings of the MPPT controllers refer to the maximum input or output current, so the current after the step-down, and the MPPT boost, needs to be factored in when sizing the controller.
Example: With a 48V array rated at 2800 Watts, the short circuit current rating of the modules will be approximately 44 amps. The rated current would be approximately 39 amps. A single FlexMax 60 could handle this current into a 48V battery, with room for the MPPT boost within the 60 amp limit (this can be adjusted to 70 amps with the FM60 as well). However with a 24V battery the same array, after the voltage step down, would potentially generate twice the current (because it is at half the voltage) and so would exceed the 60 or 70 amp rating of the controller. In other words, wiring the array at higher voltage will lower wire loss but it doesn't increase the power handling ability of the controller if the battery is at a lower voltage.
Example: With a 48V array rated at 2800 Watts, the short circuit current rating of the modules will be approximately 44 amps. The rated current would be approximately 39 amps. A single FlexMax 60 could handle this current into a 48V battery, with room for the MPPT boost within the 60 amp limit (this can be adjusted to 70 amps with the FM60 as well). However with a 24V battery the same array, after the voltage step down, would potentially generate twice the current (because it is at half the voltage) and so would exceed the 60 or 70 amp rating of the controller. In other words, wiring the array at higher voltage will lower wire loss but it doesn't increase the power handling ability of the controller if the battery is at a lower voltage.
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