![]() ![]() Continuing to pump energy into the cell faster than the chemicals can react to the charge can cause local overcharge conditions including polarisation, overheating as well as unwanted chemical reactions, near to the electrodes thus damaging the cell. There is thus a limit to the charge acceptance rate of the cell. These phenomena are non linear and apply to the discharging process as well as to charging. This is one of the reasons why cells can deliver or accept very high pulse currents, but much lower continuous currents.(Another major factor is the heat dissipation involved). The time constant associated with the charge transfer could be one minute or less, whereas the mass transport time constant can be as high as several hours or more in a large high capacity cell. The battery charging process thus has at least three characteristic time constants associated with achieving complete conversion of the active chemicals which depend on both the chemicals employed and on the cell construction. In addition there may be other parasitic or side effects such as passivation of the electrodes, crystal formation and gas build up, which all affect charging times and efficiencies, but these may be relatively minor or infrequent, or may occur only during conditions of abuse. See also Lithium Plating due to excessive charging rates or charging at low temperatures.Īll of these processes are also temperature dependent.
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