This Is One Thing Electrical Engineers Know About Smartphone Charging That You Don’t

overcharging overnight

One thing that even many electrical and electronics engineers know but other don’t “There is nothing called over-charging in a smartphone.” Yes, as shocking as it might sound, the myth has been spreading far and wide simply due to ignorance and lack of updated knowledge on how modern technology works.

While this might have been true for smartphones and devices in the previous decades since the dawn of 2000 keeping your smartphone plugged for charging overnight will not make the slightest of differences.

And we’ll explain why this is true!

Almost every battery today runs on lithium ion, but in the yesteryears, batteries were primarily made of nickel similar to the Duracell and Energizer batteries we buy in stores. Nickel-based batteries had a lot of quirks, for example having a cyclic memory which meant that if they were not fully charged between cycles, they had a tendency to forget” their full capacity and thus reduce the limit of charging.


But the major problem with both Nickel based and early lithium polymer battery was the added heating up. Leaving your device up for charging overnight in the 1990s would increase the battery temperature to dangerous limits. And as a lithium battery is capable of receiving a charge between 32 degrees to 113 degrees while it can discharge at temperatures as low as -4 degrees, which is quite a large temperature gap, a potentially a dangerous one.

For our purposes, the heating up part is of greater significance. Since a battery can’t hold more than its capacity, it will try to dissipate the excess power, i.e. charging beyond the 100% mark as heat. This is where overnight charging was dangerous as the battery levels would elevate to combustible levels, and we all know what havoc that can wreck thanks to Samsung’s notorious Note 7.

But this was the case before the turn of the millennium. After 2000, our devices have gotten smarter, and although the batteries used in mobile devices today are the same as two decades ago, the charging technology isn’t. We don’t have to worry about overheating by overcharging since power optimization and control is regulated by the software running these devices.


These software can automatically stop charging the device when the battery reaches its full capacity and converts the charger to be used the device’s primary power source. This means you can leave your phone to charge all night and enjoy that satisfying fully charged phone without worrying about waking up to a fiery pit caused by your overheated battery.

That is, of course, only true if you don’t use Galaxy Note 7.

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