1. AC Question's Avatar
    Does anyone else get inaccurate approximate times till fully charged when using a wireless charger?

    I bought a generic wireless charger off ebay and when using the exact same cable and wall power supply I get vastly different approximate charge times.

    E.g. my phone is currently at 70% and plugging the phone in directly it says phone will be fully charged in 1hr 20min

    Using the exact same cable and wall power supply using the wireless charger it says my phone will be fully charged in 40min.

    Surely this isn't possible? I have let my phone on the wireless charger and it does reach 100% in approximately 40min but I have a feeling I'm getting inaccurate battery readings. I've also installed ampere and it doesn't seem able to give me a charging rate when using the wireless charger.

    Any thoughts / ideas appreciated.
    07-11-2015 04:03 AM
  2. Rukbat's Avatar
    State of Charge (like the 50% you see) and time left are rough estimates based on rough estimates. About the only accurate values are 0% (which will destroy a lithium battery) and 100%.(if you calibrate the calibration file after the terminal voltage on the battery stops rising during charging).

    The State of "charge" is actually the terminal voltage on the battery with an algorithm applied to it to derive the amount of charge in the battery. But the charging voltage has to be higher than the battery voltage to charge the battery (current flows from higher voltage to lower voltage), so that's two inaccuracies right there - the fact that "state of charge" isn't, and that the voltage being measured is somewhere between the charger voltage and the battery voltage, but the algorithm is being applied as if it were the battery voltage.

    Use state of charge and time to full charge as estimates, not absolutes.

    (1 hour, 20 minutes for a 30% charge seems pretty inaccurate. That's way under the rate of charge most phones put to the battery.)
    08-23-2015 12:53 AM

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