Does 'Slow charging' save electricity ???

edited September 2021 in ZenFone 6

I like the addition of these battery care options in Asus devices, so the other day, I decided to use the slow charging feature to preserve my battery in the long run. But I wonder, keeping the phone on charge for longer might waste more electricity than normally charging it at 18w. I understand that if it charges at 10w it saves some electricity. But then again, is charging at 10w saving more electricity than charging at 18w, in one full charging session ???


  • _jis__jis_ Level 5

    Slow charging will take longer, fast charging will take less time.

    One would think that energy consumption should be similar:

    Less current for a longer time ~ more current for a shorter time.

    But let's not forget the higher losses during fast charging, when some of the delivered energy is converted to heat. Therefore, I believe that fast charging will be less efficient.

  • Hi, the software automatically uses and charges battery, it helps battery efficiency. Charging a phone slow or fast there won't be a massive change in saving electricity.

  • _jis__jis_ Level 5

    I finally found the time to back up my reasoning with measurements.

    I measured with TC66C.

    Phone charged from original Asus Charger & original 91cm Cable: 

    • range 40% => 81%
    • power max 14.25W
    • voltage 9V
    • energy 9812mWh

    Phone charged from Chromebook via USB-C/USB-C 22.5cm Cable: 

    • range 40% => 81%
    • power max 10.84W
    • voltage 4.65V
    • energy 9626mWh

    So as everyone can calculate, we saved less than 2% of energy by charging more slowly. It's possible that 5W charging would have saved a little more, but I didn't have that much time to make such a measurement because I wasn't allowed to use my phone during the whole measurement so as not to distort the measurement.

This discussion has been closed.