Switching Shunt Charge Controollers
Switching shunt charge controllers allow maximum array current to flow into the battery through a blocking diode, until the battery voltage reaches the charge termination set-point. At this point, a shunt transistor will turn on, shorting out the solar array, halting any further battery charging. When the battery voltage drops to the charge resumption set-point, the shunt transistor will turn off and charging will resume. The result is that when battery capacity is low, charging will be continuous. As the battery charges up, current will pass into the battery for shorter and shorter periods, until at full charge, it will pulse current into the battery to achieve and maintain full charge.
Switching shunt charge controllers are an ideal choice when noise interference needs to be eliminated for wireless applications.