I've a battery charger that can output 9v and 2.5A and I use full power from it that is 22.5W.

Can I translate this power consumption from DC to AC current?

My AC is 220V 50Hz, so I'll consume 22.5Wh when I charge my battery like a big lamp?


On device is also written 110V-240V 50Hz/60Hz and Max. consumption 0.68A related to AC.

  • \$\begingroup\$ Lamp what? Don't mix the power and energy. \$\endgroup\$ – Eugene Sh. May 20 '16 at 17:07
  • \$\begingroup\$ Keyword: efficiency. Google for it. \$\endgroup\$ – Jakub Rakus May 20 '16 at 17:08
  • \$\begingroup\$ Yes, I know that efficency is no 100% for a transformer, I'm asking just if this convertion is correct. \$\endgroup\$ – Singee May 20 '16 at 17:10

You'll take a little bit more than 22.5 watts from the AC outlet because a battery charger (a power supply) is a converter that is never 100% efficient. Typically modern converters are good for 85% efficiency so you'll take more like 27 watts from the AC and this is what you'll be billed for by the utility.

Regards what is written on the device, this is unrelated to actual power consumption.


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