Characteristics of Li-Cells
During the last decade Lithium batteries have replaced other battery types in many applications. The main reasons for this are their ability to store large amounts of energy in a small volume and their light weight. The gravimetric or volumetric energy density is much greater than in other secondary batteries. This makes them particularly suitable for laptops, handheld tools and lights. They have, depending on the cell chemistry, a low internal resistance and therefore can supply high currents. The recharge time is in the range of 3-4h. They have no or only a very limited fast charge capability.
Unfortunately, the benefits are offset by some disadvantages. Lithium is a highly reactive light metal. If operated outside a by the manufacturer specified save area they can easily ignite and cause fire or even explode. Especially dangerous are short circuits and overcharging due to a defective charger, since this can lead to a strong heating of the cells. A single deep discharge below a certain boarder will damage them permanently. Lithium battery packs are therefore always fitted with an additional safety circuit, whose job it is to prevent these operating states. It simply separates the entire pack from the charger or the load if operated outside the save area. The safety circuit monitors the voltages of each single cell in a pile of in series-connected cells, the charge or discharge current and the temperature of the pile. Improving the intrinsic safety of the cells is a main goal of the cell manufacturers. For this reason some cell types (eg lithium cobalt) have lost their importance while the spread of other cell types increases.
To learn more, visit our Battery seminar at akkuman.de. It is performed in a more or less regular intervals. Ask akkuman.de for the next date, the venue and the costs.
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