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Battery Chargers

Last Updated: May 2010
See the federal standards main page to view current status

THE PRODUCT: A battery charger is a device that charges batteries for consumer products, including battery chargers embedded in other consumer products. Examples include cordless phones, cellular phones, power tools, laptops, etc.

POTENTIAL STANDARDS: No efficiency standards currently exist for battery chargers. The California Energy Commission (CEC) adopted a voluntary comprehensive test procedure for battery charger systems in December 2008 (CEC 2008b; PG&E 2008c). While technologies exist that could dramatically reduce energy consumption, until 2008 there was no widely accepted testing procedure for charger efficiency. To address this issue, PG&E and its technical consultant, Ecos Consulting, collaborated with Southern California Edison (SCE), the CEC, and industry stakeholders to develop a comprehensive test procedure for energy consumption of battery chargers in active, maintenance, and no-battery mode. While California has adopted this voluntary test procedure, there are also three other test methods available; however, these three other test methods do not cover all the modes of operation for all battery charger systems (PG&E 2009).

EISA 2007 provided a timeline to evaluate energy conservation standards for battery chargers, mandating that a standard be set by June 1, 2011, becoming effective in 2014. We analyzed Tier 2 standards proposed by PG&E that differentiate between small and large battery chargers and would set a stringent limit on the energy consumption of battery chargers in active, standby, and maintenance mode (discussed below) and require a minimum power factor (PG&E 2009). Our analysis focused only on small battery chargers, however, as the federal standard will be limited to chargers connected to or embedded within "consumer products," which does not include industrial equipment that utilize battery chargers, such as fork lifts. We estimate that the proposed Tier 2 standard level would save 127 TWh (about 1.3 quads of primary energy) cumulatively by 2030 and generate $5.8 billion in net present value savings.

KEY FACTS: Battery chargers consume almost 42 TWh per year nationally, or around 14% of the total electricity consumption of electronic devices (CEC 2008a). 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. We estimate that setting standards for no-battery and maintenance mode would reduce per unit electricity consumption by 30%. Again, this ignores the potential savings of chargers in active mode.

Active mode efficiency and maintenance mode efficiency are interrelated in battery chargers. There are some essential functions of battery chargers that are carried out in maintenance mode, such as leveling the charge for batteries that have multiple cells, which are similar to active mode functions. Improving the efficiency of battery chargers in maintenance mode will therefore have an impact on the energy consumed in active mode. Before standards are set for active mode energy consumption, it is important that the interaction effects of chargers in maintenance and active mode are better understood and clearly represented by some sort of efficiency metric. As mentioned above, California has developed metrics for estimating energy use in active mode and is considering standards based on those metrics for products outside the scope of the federal rulemaking. DOE will be analyzing active mode efficiency in the pending rulemaking, which will allow new federal standards to cover active mode if warranted.

There is no recent ASAP activity regarding battery chargers.