How do battery chargers know when a battery is fully charged?
In: Technology
I think you are questioning the wrong thing. How does the dish knows when I’ve finished my lunch? The charger itself knows nothing nor it has the capability to do that. It is basically the device itself (it could be the phone, or whatever thing) that has voltage resistances and detectors to know when the battery is full and to stop charging, it is not the charger but the device
The simplest battery charger is a just a voltage source. When a battery is “dead” its voltage is lower than normal. When you attach the charger, since the charger’s voltage is higher, electric charge flows from it into the battery.
As the battery fills up with charge, the voltage rises. Eventually the voltage is the same as the charger and so no electric charge flows.
More complicated charges have a second stage that is trigged when the current drops to a certain level.
Smartphone chargers are actually built into the phone and do all sorts of fancy stuff while the phone is charging and most of that stuff is beyond the scope of EL5 in my opinion.
Batteries produce a differing amount of voltage depending on how charged they are. And most devices that use batteries have device in them that either increases or lowers the voltage. Usually to either 5 or 3.3, this is why it can take a second for a device to power down when you remove the batteries when it’s still active.
But if you have a device that reads the change in voltage straight from the battery, you can make a rough estimate of how dead the battery is.
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