An article published on the naked scientists.com years ago states, not all of the energy which you use to charge a battery will come out of the battery in the end. That remains true today. If you look at the efficiency of charging standard, nickel cadmium, or nickel metal hydride battery, the efficiency is about 60 to 70%, so you’re wasting 30 or 40% of the energy you’re putting into the battery itself.
If you feel that a battery while it is being charged you will find it gets warm. This indicates energy is being wasted. You’re also wasting some more energy in the charger because the “transfer” is not 100% efficient either. So, you might be talking about half the energy you’re using actually ending up in that battery. While 60% efficiency doesn’t sound very good, it’s far, far better than what is achieved in a throw-away battery, they are often said to be only 1 or 2% efficient. That’s because you’ve got to get materials to make the battery, you’ve got to refine them, and you’ve got to put them all into a case.
|Table 1: Battery efficiencies [1-3]|
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