Nickel hydrogen batteries, lithium ion batteries, nickel-cadmium batteries, what is the difference between the three

Nickel hydride batteries

Nickel-metal hydrogen batteries are synthesized with hydrogen ions and metal nickel. The power reserve is 30 % higher than that of nickel-cadmium batteries. It is lighter than nickel-cadmium batteries, has a longer service life, and has no pollution to the environment and has no memory effect. The disadvantage of nickel-metal hydride batteries is that nickel-cadmium batteries are much more expensive and have worse performance than lithium batteries.

Lithium-ion batteries

A high energy density battery made of lithium-ion batteries. Lithium-ion battery is also a smart battery that can be combined with a dedicated original smart charger to achieve the shortest charging time, maximum life cycle and maximum capacity. Lithium-ion batteries are currently the best performance batteries. Compared with nickel-cadmium batteries and nickel-metal hydride batteries of the same size, the power reserve is the largest, the weight is the lightest, the life is the longest, the charging time is the shortest, and there is no memory effect.

Rechargeable batteries are mainly lead-acid batteries and alkaline batteries. The nickel-cadmium(NiCd), nickel-metal hydride(NiMH) and lithium-ion(Li-Ion) batteries currently in use are alkaline batteries.

The NiMH battery positive plate material is NiOOH, and the negative plate material is a hydrogen absorbent alloy. The electrolyte usually uses 30 % of the KOH aqueous solution and adds a small amount of NiOH. The diaphragm is made of Kongweinilun non-woven cloth or nylon non-woven cloth. The NiMH battery has two types: cylindrical and square.

NiMH batteries have good low-temperature discharge characteristics. Even at -20 °C ambient temperatures, large currents(at 1C discharge rate) are used to discharge, and the amount of electricity emitted can reach more than 85 % of the nominal capacity. However, at high temperatures(above +40 °C), the storage capacity of the NiMH battery will decrease by 5 to 10 %. This loss of capacity due to self-discharge(the higher the temperature, the greater the self-discharge rate) is reversible, and several charge and discharge cycles can return to maximum capacity. The open circuit voltage of the NiMH battery is 1.2 V, which is the same as the NiCd battery.

The charging process of the NiCd/NiMH batteries is very similar and requires constant current charging. The difference between the two is mainly in the fast charging termination detection method to prevent the battery from overcharging. The charger performs constant current charging on the battery, and also detects the battery voltage and other parameters. When the battery voltage slowly rises to a peak, the rapid charging of the NiMH battery terminates, while the NiCd battery terminates the rapid charging when the battery voltage drops by a-<UNK> V for the first time. To avoid damaging the battery, the battery can not start charging quickly when the temperature is too low. When the battery temperature Tmin is below 10 °C, it should be transferred to the trickle-down charging method. Once the battery temperature reaches the specified value, it must stop charging immediately.

Nickel-cadmium batteries

The active material on the positive plate of the nickel-cadmium battery NiCd battery consists of nickel oxide powder and graphite powder. Graphite does not participate in chemical reactions and its main role is to enhance conductivity. The active material on the negative plate consists of cadmium oxide powder and iron oxide powder. The role of iron oxide powder is to make cadmium oxide powder have higher diffusion, prevent agglomeration, and increase the capacity of the polar plate. The active substances are respectively wrapped in perforated steel belts and become positive and negative plates of the battery after pressurized molding. The plates are separated by a hard rubber insulator with alkali resistance or a porous polyvinyl corrugated plate. The electrolyte usually uses a potassium hydroxide solution. Compared with other batteries, the NiCd battery has a moderate self-discharge rate(ie, the rate at which the battery loses its charge when it is not in use). During the use of the NiCd battery, if the discharge is not fully charged, the next discharge will not release all the electricity. For example, after releasing 80 % of the electricity, the battery can only emit 80 % of the electricity. This is called the memory effect. Of course, several complete discharge / charging cycles will return the NiCd battery to normal operation. Due to the memory effect of the NiCd battery, if it is not fully discharged, each battery should be discharged below 1V before charging.

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