A battery charger is a device that charges batteries for consumer or non-consumer products, including battery chargers embedded in other products. Examples of consumer battery chargers include chargers for cordless phones, cellular phones, power tools, laptops, and golf carts. Non-consumer battery chargers include chargers for two-way radios, emergency backup lighting, and lift trucks.
No efficiency standards currently exist for battery chargers though a DOE rulemaking is currently underway. A proposed rule was issued in March 2012. Due to questions raised by stakeholders during the comment period, DOE published a Request for Information in March 2013, asking for more information about products certified as compliant with the California Energy Commission battery charger standards. DOE reviewed the data to determine if the analysis prepared for the proposed rule needs to be revised in light of the availability of more efficient products. In September 2015, DOE issued a supplemental proposed rule.
The 2012 ASAP/ACEEE report, The Efficiency Boom, analyzed standard levels from the September 2010 DOE preliminary analysis for consumer battery chargers that represent the minimum life-cycle cost point. On average, the standard levels represent energy savings of about 60% relative to baseline products and can be achieved using switched-mode rather than linear power supplies, improved charge control circuitry, and limiting power when the battery is full or no battery is present. Lower electricity bills would cover the typical incremental cost for more efficient battery chargers (about $4) within three years. Non-consumer battery chargers standards were not analyzed in the report. The report estimates that standards for consumer battery chargers would save the U.S. 6.3 TWh on an annual basis in in 2035 and generate $970 million in net present value savings.
The California Energy Commission (CEC) completed state-level standards for both consumer and non-consumer battery chargers in January 2012 which took effect in 2013 for consumer chargers and 2014 for industrial chargers. California standards for consumer chargers will be preempted once national standards go into effect, but state standards for non-consumer chargers will remain in effect. In 2013, Oregon adopted similar standards for battery chargers which went into effect January 1, 2014.
Battery chargers operate in three modes: no-battery, maintenance, and active mode. In no-battery mode, the charger is plugged into the wall but is not connected to a battery. In maintenance mode, the battery is fully charged yet still connected to the charger. In active mode, the battery is in the process of being charged. To ensure energy savings in the field, it is important that battery chargers are efficient in all three modes of operation since the amount of time spent in each mode varies significantly among products and among users of a given product. Inefficient battery chargers often continue to provide constant current to the battery even after the battery is fully charged. Simple solutions can be applied to significantly reduce power consumption in maintenance mode.
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Timeline reflects state standards from 2001 to present; federal standards from inception to present.