What is the difference between Nickel-cadmium batteries and nickel-metal hydride batteries ?
Rechargeable batteries and ordinary battery differences: In addition to the two terminal voltage is different, there are two differences: First, the internal resistance of rechargeable batteries is much lower than ordinary batteries, such as using a digital multimeter to measure a 5 Ordinary battery short-circuit current, the value is generally below 3A, and measuring a nickel-cadmium or nickel-metal hydride batteries on the 5th of the short circuit current, usually above 4A, precisely because of this, we determine the true and false NiCad, NiMH When the battery can be used to measure the instantaneous short-circuit current to distinguish. Second, nickel-cadmium, nickel-metal hydride rechargeable batteries and ordinary battery discharge characteristics are different, especially when the performance of the discharge termination. Ordinary batteries in the discharge process, the terminal voltage is gradually increased with the increase in discharge from 1.5V decreased, there is no sudden changes in terminal voltage, while the nickel-cadmium and nickel-metal hydride batteries are different during the discharge process Terminal voltage almost does not change with the amount of discharge, but once the discharge is completed. Terminal voltage dropped from about 1.2V to 1.0V or so, this time the discharge current also doubled. In the terminal voltage drop with 1.0V below the continued discharge is called over-discharge, damage to the battery, affecting life expectancy.
We currently use the rechargeable batteries, generally according to their chemical composition can be divided into four categories, namely, NiCd, NiMH, PbSO4 and Li + ). Here's a brief introduction of these four types of rechargeable batteries:
(A) lead-acid batteries: it is an earlier appeared a rechargeable battery, which is commonly used car battery. There are two types of ordinary lead-acid batteries and valve pull-sealed lead-acid batteries. The former is gradually replaced by the latter due to inconvenient use and serious environmental pollution. The emergency lights we use are generally these batteries, the normal cycle life of 1000 to 1200 times.
(B) nickel-cadmium batteries: it is also an earlier battery. That is commonly used by everyone now Walkman rechargeable battery. A single battery has a nominal voltage of 1.25V and its capacity (the capacity of the rechargeable battery is expressed in terms of current (mA) times hours (h) .If a battery has a capacity of 500MA, it indicates that the battery can discharge at 500MA Hour) For the general No. 5 battery (AA type) between 450 ~ 800MA, the number of normal cycle charging more than 500 times, but if used incorrectly, will greatly reduce the number of its use. Nickel-cadmium batteries have a phenomenon called "memory effect". When people do not discharge the finished nickel-cadmium batteries, the battery will automatically "remember" live this one without discharge completely. The next charge reaches this point, it will show the same characteristics of the battery discharge completed. So although the battery is not discharged completely, but at the same time reduced capacity, which is the so-called "memory effect", its essence is produced in the electrode dendrite, this "memory effect" is unique to nickel-cadmium batteries of. It will seriously affect the battery capacity, reducing the battery life, so the nickel-cadmium in the battery before charging it to be fully discharged, so that after the discharge will be recharged, we do not repeatedly use such batteries Charge the battery, the vast majority of commercially available chargers will automatically charge low charging current is very small, the battery is full at least 15 hours and less discharge function, the battery is more damaged. Some of the better features of the charger in the confirmation can be quickly charged, it entered the preconditioning phase, at this stage, the battery charger to fully discharge, so that each battery is fully discharged, so that each battery voltage dropped to about 1.0v , To eliminate the "memory effect" of nickel-cadmium batteries. After the nickel-cadmium battery pretreatment, directly into the fast charge stage, after the quick charge into the trickle charge, the time required is generally 2-3 hours.
(C) NiMH battery: It is a newly developed new rechargeable battery, its performance and nickel-cadmium batteries similar, but its higher energy density. A NiMH 5 NiMH battery capacity between 1000mah to 1300mah, in addition, it does not exist "memory effect", no pollution to the environment, so some people call it "green battery", of course, the price is relatively high.
(D) lithium-ion battery: It is also the recent development of the battery, the biggest advantage is that the higher the energy density, but its price is also high, generally used in high-block electronic products, but not to discharge more than the discharge voltage, But also not greater than the discharge current discharge.
In order to properly use all kinds of rechargeable batteries, battery full Ting long battery life, the correct charging of the battery is very crucial, if the charging method is not correct, will greatly shorten the battery life.