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Old 07-30-2015, 11:13 AM   #11
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Join Date: May 2012
Posts: 357
If you're building a system with multiple panels, make sure you get an MPPT charge controller with a maximum input voltage higher than n times the open circuit voltage of your panels where n is the number of panels you have. This will allow you to wire the panels in series, providing a higher input voltage at lower current than wiring them in parallel. This cuts down the size of the wire you need between the panels and from the panels to the charge controller because power losses in the wire are proportional to the square of the current - 1/4 the current = 1/16 the losses. MPPT controllers are designed to use a high input voltage and low output voltage to charge the batteries. They also will draw power from the solar array at the panel's maximum power production voltage which can increase the power output from the panels by 10% or more. MPPT chargers are always multi-stage chargers which do a better job of charging your batteries than the older PWM (Pulse Width Modulation) models. MPPT chargers are also available that internally record all kinds of information about the charging system. You can connect to the charger with a computer and read out all of the stored information.

Always carefully read the specs for a charger, and if possible reader comments before purchasing. One company sells "MPPT" chargers that aren't multi stage, don't run the solar panels at optimum voltage, and tend to fail within a few months.


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