NiMH battery

NiMH battery is composed of hydrogen ion and metal nickel. Its power storage is 30% more than that of nickel cadmium battery, lighter than that of nickel cadmium battery, longer service life, no pollution to the environment and no memory effect. The disadvantage of NiMH battery is that the price of NiCd battery is much more expensive, and its performance is worse than that of lithium battery

Lithium ion battery

A high energy density battery made of lithium ion battery. Lithium ion battery is also a kind of smart battery. It can cooperate with special original smart charger to achieve short charging time, large life cycle and large capacity. Lithium ion battery is a battery with good performance at present. Compared with nickel cadmium battery and nickel hydrogen battery of the same size, it has large power storage, light weight, long service life, short charging time and no memory effect

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

The positive plate material of NiMH battery is NiOOH, and the negative plate material is hydrogen absorbing alloy. The electrolyte is usually 30% KOH aqueous solution, and a small amount of NiOH is added. The membrane is made of porous vinylon non-woven fabric or nylon non-woven fabric. NiMH batteries are available in cylindrical and square shapes

NiMH battery has good low temperature discharge characteristics. Even under - 20 ℃ ambient temperature, if large current (at 1C discharge rate) is used for discharge, the discharge capacity can reach more than 85% of the nominal capacity. However, the storage capacity of NiMH battery will decrease by 5-10% at high temperature (above+40 ℃). This capacity loss caused by self discharge (the higher the temperature, the greater the self discharge rate) is reversible, and several charge discharge cycles can restore to large capacity. The open circuit voltage of NiMH battery is 1.2V, which is the same as that of NiCd battery

The charging process of NiCd/NiMH batteries is very similar, requiring constant current charging. The difference between the two is mainly in the termination detection method of fast charging to prevent the battery from overcharging. The charger charges the battery with constant current and detects the voltage and other parameters of the battery. When the battery voltage slowly rises to a peak, the quick charging of NiMH battery is terminated, while NiCd battery stops when the battery voltage drops by one - △ V each time. To avoid damage to the battery, rapid charging cannot be started when the battery temperature is too low. When the battery temperature Tmin is lower than 10 ℃, the trickle charging mode should be switched to. Once the battery temperature reaches the specified value, the charging must be stopped immediately

Nickel cadmium battery

The active substance on the positive plate of NiCd battery is composed of nickel oxide powder and graphite powder. Graphite does not participate in chemical reaction, and its main function is to enhance conductivity. The active substance on the negative plate is composed of cadmium oxide powder and iron oxide powder. The role of iron oxide powder is to make cadmium oxide powder have high diffusivity, prevent caking, and increase the capacity of the plate. The active substances are respectively wrapped in perforated steel strips, which become positive and negative electrode plates of the battery after being pressurized and formed. The plates shall be separated by alkali resistant hard rubber insulating rods or perforated PVC corrugated plates. The electrolyte is usually potassium hydroxide solution. Compared with other batteries, NiCd batteries have a moderate self discharge rate (i.e. the rate at which the battery loses its charge when not in use). During the use of NiCd battery, if the discharge is incomplete and the battery is charged again, the next time the battery is discharged, it cannot discharge all the power. For example, if the battery is fully charged after 80% of the power is discharged, the battery can only discharge 80% of the power. This is called memory effect. Of course, several complete discharge/charging cycles will enable the NiCd battery to resume normal operation. Due to the memory effect of NiCd battery, if it is not fully discharged, each battery shall be discharged to below 1V before charging