07 January 2012

LITHIUM-ION BATTERY TECHNOLOGY

The way ahead on battery technology -

Lithium-ion technology represents a quantum leap in the world of cordless power tools. Whereas cordless tools used to have the disadvantage that the reserves of current were relatively low and the intake capacity could noticeably decline after a number of charge cycles, these aspects are made less important by Li-Ion technology.

One of the biggest advantages of the Li-Ion battery is its high energy density. The energy density describes the amount of energy in relation to the weight of a battery. The energy density of a Li-Ion battery can be more than twice that of NiMH (Nickel Metal Hydride) and NiCd (Nickel Cadmium) batteries.

This means that the same power tool can be operated for twice as long with a Li-Ion battery as with an NiMH battery.

Equipped with higher power reserves, the Li-Ion battery demonstrates its second big advantage: it has no memory effect and only minimal self-discharge.

In practice, this means that after every recharge the full battery capacity of power is actually available.

In contrast, NiCd batteries have a memory effect. This is the name given to the loss in capacity that occurs as a result of very frequent partial discharging of a nickel cadmium battery. The battery seems to remember the energy requirement, and over time it provides only the amount of energy required for previous discharge cycles instead of providing the original amount of energy. This ultimately results in a reduction of the usable capacity of the battery.

Nickel metal hydride batteries are less affected by memory effect than NiCd batteries, but they are sensitive to overcharging and deep discharge. The effect of this, however, is essentially the same as memory effect: the battery capacity is significantly reduced.

When applying Li-Ion technology in its power tools, Bosch for example uses two additional technologies that both protect the battery and also enable very fast and gentle charging. ECP (Electronic Cell Protection) protects the battery against overload and overheating.

The special Hyper Charge technology for Li-Ion batteries protects the cells against overcharging. Due to the gentle rapid charging process, the batteries are charged to 75% after only half of the charge time.

Together these two technologies ensure up to 400% longer lifetime for the Bosch lithium-ion batteries and provide permanently high battery capacities, which leads to an optimum runtime of the cordless power tool.

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