Is it harmful to charge electronics too long?

The mordern days batteries are safe , the have overcharge protection circuits to ensure safty. Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V on a Li-ion designed for 4.20V/cell will plate metallic lithium on the anode. The cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises and if the charge is allowed to continue, the current interrupt device (CID) responsible for cell safety disconnects at 1000–1,380kPa (145–200psi). Should the pressure rise further, a safety membrane on some Li-ion bursts open at about 3,450kPa (500psi) and the cell might eventually vent with flame.

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