Batteries are accumulators of the energy passed on from the energy source, either a solar panel, wind turbine, or micro hydro system. In renewable energy power systems, it is recommended that batteries are installed to store energy when it isn’t being used so that power is available at night or on a cloudy or rainy day. Pro Solar Engineering sells two reputable brands of batteries: Trojan and Atlantis Solar, along with other brands if requested. The Trojan batteries are wet, while the Atlantis Solar batteries are sealed. The batteries available for purchase range from 2 to 12 volts and from 100Ah to 2000Ah.