If you have a simple off-grid setup with just one panel or even a few solar panels and several batteries, the other vital ingredient is a charge controller that regulates the power going from the panel to the battery and shuts off power input when the batteries are fully charged.
This makes the process of running your own power station almost maintenance free.
When you are starting up its best to buy a medium-priced controller so that you can add a few panels and batteries to the mix before having to upgrade. The HQRP 20A Solar Panel Battery Charge Controller / Regulator 12V / 24V 20 Amp 300W with PWM Type of Charging retails at under $50 on Amazon.
If you do not mind spending an extra $75, you can buy an MPPT circuit solar controller — these are more elaborate than normal charge controllers. The voltage of the solar panel changes with time of day and temperature. The optimum voltage for battery charging changes as the state of charge of the battery. The MPPT charge controller matches these voltages and can result in 30% more efficient transfer of power. This means good MPPT solar charge controllers can reduce the number of solar panels needed by up to 30%- a tremendous benefit. Even if the excess panels are purchased, benefits are realized in a Grid Tie system because more electricity can be sold back to the grid. While only a small part of system price, a MPPT solar panel charge controller can leverage the rest of the system to better performance.
If you are starting with several small panels then you might try the Sunforce 60032 30 Amp Digital Charge Controller as this will allow you up to 300 Watts of solar power.
the main function of charge controller is to stop you frying your batteries by overcharging them once they are already full. But they also input the power at a steady rate.WARNING: one comment below mentions that they connected their Sunforce Charge controller to a setup with too much solar power incoming, and it “fried straight away.”
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