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Charge Controllers

Every battery-based renewable energy system requires charge control. A solar charge controller brings your batteries to optimum charge level by monitoring voltage and limiting battery current as appropriate. For solar arrays over 200 Watts, an MPPT controller is almost always more economical when the power system is considered as a whole. With wind or hydro power sources, an additional PWM type controller is often used in addition to the MPPT. The MPPT operates the solar array at its best possible performance, while a PWM can be configured to divert excess power to a diversion load – water and air heating elements.

Temperature compensation is important – voltage requirements for batteries are different at different temperatures. To prevent overcharging in the summer and undercharging in the winter, use temperature compensation probes whenever possible, and if not available, adjust charge voltage setpoints appropriately.

"On average, an MPPT solar charge controller delivers about 15% more energy per year than a standard controller. And it does its best work in winter, when most off-grid homes need all the charging help they can get."

Solar Living Sourcebook 14th Edition
Chapter 4: From Panel to Plug

Charge Controllers & MPPT Controllers from Real Goods