A solar charge controller is needed if you choose to store the solar panels electricity in solar batteries. As we all know the intensity of the sun energy is totally controlled by nature and there is no guarantee the electric solar panels will produce a constant amount of electricity. A reliable solar charge controller will allow the uncertain solar panels’ voltage to safely charge the batteries. Without this controller you can potentially overcharge your batteries and damage the devices connected to it. For lead acid batteries overcharging may lead to internal crystallization which reduces the batteries’ lifespan. » Read more: Solar Charge Controller