Schneider Electric It Corporation

American Power Conversion Corporation

Ramakrishnan Madenoor Krishnan

Sreejakumar Sreekantan Nair

Milind Dighrasker

Narayana Prakash Saligram

Disclosed are methods for charging batteries utilizing a charge balance approach, and charger systems using those methods. In one example, a method for charging a battery includes monitoring an amount of charge released by the battery while in a discharge state, recording the amount of charge released while in the discharge state, applying a voltage which results in current in reverse direction to the battery at a first voltage level for a time sufficient to introduce an amount of charge substantially equal to the recorded amount of charge released by the battery while in the discharge state, and maintaining the battery in a stand-by mode by applying a voltage which results in current in reverse direction to the battery at a second voltage level, the second voltage level being in a range sufficient to prevent self-discharge of the battery and insufficient to induce evaporation of electrolyte in the battery.

Battery charging method and apparatus

Aspects of the invention are directed to methods and apparatus to protect an inverter from failure due to neutral lifting. In one aspect, the present invention provides a method of controlling an inverter in a UPS, the inverter being selectively coupled to a power line and comprising an input to receive an input voltage from the power line. The method comprises acts of monitoring the input voltage, detecting based on the act of monitoring, that the input voltage exceeds a predetermined high threshold value, isolating the inverter from the power line responsive to detecting that the input voltage exceeds a predetermined high threshold value, determining whether or not a neutral lifting condition exists on the power line, indicating that the inverter is in a fault state if the neutral lifting condition exists, and reconnecting the inverter to the power line if the neutral lifting condition does not exist.

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Karnataka, India

Ramakrishnan Madenoor Krishnan