Operational modes and charging techniques for secondary batteries

In applications such as load levelling, motive power or in consumer electronics, the battery is required to undergo a sequence of deep discharges followed by a recharge to maximum capacity. A number of methods may be used. 

With this method, control equipment is simple and inexpensive and it is straightforward to calculate the charge delivered. However, if high currents are used, problems are encountered with batteries which have porous electrode structures because of non-uniform current distribution, and severe gassing may occur towards the end of the charge. At low current, 

Sealed nickel-cadmium and nickel-metal hydride sealed cells for consumer equipment now generally employ charge control circuits which permit fast charging. A number of methods are used to detect the onset 

Here the consumer circuit is either connected to the mains supply and a battery-powered inverter and transformer system, or the latter supplies 

It must be emphasized that the most appropriate charging regime is very dependent on the cell system under consideration. Some are tolerant to a considerable amount of overcharging (e.g. nickel-cadmium batteries), while for others, such as zinc-silver oxide and most lithium secondary cells, overcharging can result in permanent damage to the cell. Sealed battery systems require special care float charging should not be used and trickle charge rates should be strictly limited to the manufacturer s recommended values, since otherwise excessive cell temperatures or thermal runaway can result. 

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Appendix 1 Operational modes and charging techniques for secondary batteries... 

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