Why does a laptop say it’s at 6-8% charge, and then it dies, but when it’s at a higher charge, going from 60% to 59% takes a while?
In: Technology
Many battery indicators are not well calibrated. Battery monitoring circuits measure the voltage and the current coming from a battery, but do not directly see the amount of charge in the battery.
Software programs estimate that from the voltage and the current measurements, but doing so is somewhat of a black art. Good software algorithms keep records of past performance of the battery to estimate the charge state more accurately, but when a battery can be changed, it may take some time to recalibrate the algorithms.
Laptops (as with other devices) require a certain amount of power to operate, and when they sense the battery is nearly empty, attempt to shut down in an orderly way.
Older batteries may take longer than new batteries to charge up, and may not hold as much charge. Battery charging circuits may push a lot of current into a battery that’s nearly completely discharged, then reduce the current as the battery approaches maximum capacity.
Devices may also measure the temperature of the battery to best charge the battery without damaging it by overheating. (Off topic observation: Tesla cars use battery power to warm the battery itself, as well as a cooling system to keep the batteries from getting too hot.)
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