![]() ![]() Stand-Alone Fast Charger for Li-Ion Rechargeable BatteriesĬharging Li-Ion rechargeable batteries is simpler than charging NiMH batteries because it is not necessary to monitor the rate of voltage change (dV/dt). This flow diagram illustrates the charging procedure implemented by the IC in Figure 3. 0.165V) is exceeded, indicating the internal battery resistance plus contact resistance is higher than 150mΩ the IC asserts a logical or optical error message (LED1, LED2) and stops the charging procedure (Figure 4).įigure 4. Table 1 provides an overview of the key characteristics of each battery type. In turn, this capability makes them suitable for small, highly portable appliances. Li-Ion rechargeable batteries are more expensive, but they have a substantially higher energy density and can, therefore, deliver more performance for a given size. Comparison of the memory effect in NiCd's and the lazy effect in NiMH's. Like the memory effect, the lazy effect prevents full use of the capacity in a rechargeable battery both effects, however, can be avoided by using chargers with a discharge function.įigure 1. The lazy effect results from the crystallization of a portion of the nickel. Their discharge currents are lower, but they suffer from the lazy effect, which is a weaker version of the memory effect in NiCd batteries. NiMH batteries are more environmentally friendly than NiCd's, but they also cost more. As a consequence, European Regulation 2000/53/EG forbids the sale of NiCd rechargeable batteries, effective December 31, 2005. These early types of NiCd batteries turned out to be an ecological as well as an economical burden when disposing of defective batteries. Another disadvantage of NiCd batteries is the poisonous cadmium (Cd) in its active material. The resulting memory effect yields a battery with lower capacity and a lower terminal voltage, causing the NiCd battery to reach the minimum usable terminal voltage (shutoff point) sooner than desired (Figure 1). (Cadmium crystals at the anode of a fresh battery are approximately one micrometer thick.) If such a NiCd battery is recharged before being fully discharged, some active material (as much as 100µm on the anode's cadmium side) remains unused and begins to crystallize, thereby removing itself from the chemical action. On the other hand, NiCd batteries once suffered from the so-called memory effect (modern NiCd's seldom do), which reduces battery capacity. Because NiCd's provide the highest level of discharge current, they were also used in applications that required high levels of power for short periods of time. ![]() ![]() NiCd batteries were especially popular in low-cost applications because they were cheaper than NiMH and Li-Ion batteries. ![]() Nickel-metal-hydride (NiMH) and lithium-ion (Li-Ion) rechargeable batteries came later, appearing on the mass market toward the end of the nineties. Portable appliances in the mid-1980s-such as DECT phones, cassette players, and electric shavers-were powered mainly by nickel-cadmium (NiCd) rechargeable batteries. The article then describes how to safely fast charge NiMH and Li-Ion rechargeable batteries in a stand-alone configuration, without using a microcontroller or a power-surge-protected mains adapter. This application note provides an overview of rechargeable battery chemistries it details their typical characteristics and important considerations for selecting a battery type. Using rechargeable batteries tremendously reduces the amount of hazardous materials dumped into our environment, the consumption of materials, and the energy required to produce the equivalent in non-rechargeable batteries. Even more important are the environmental benefits of rechargeable batteries. As a consequence of this high level of power consumption in portable devices, the use of a rechargeable battery has become more cost effective than using a standard battery. The reasons are several: an ongoing integration of functions (such as a mobile phone with a digital camera), the higher computing speed in notebook computers, and the convenience of large color displays. Even as power levels are falling, the absolute amount of power consumed by rechargeable batteries is rising. Rechargeable batteries are the standard power source for today's products, especially for portable appliances such as notebook computers, mobile phones, and digital cameras. This application note provides an overview of nickel-cadmium (NiCd), nickel-metal-hydride (NiMH), and lithium-ion (Li-Ion, Li+) rechargeable batteries, discussing their characteristics and explaining how to safely fast charge NiMH and Li-Ion rechargeable batteries in a stand-alone configuration, without the use of a supervising microcontroller. ![]()
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