Based on Table 1 analysis, it is not difficult to see that there are certain differences in performance between cadmium nickel alkaline batteries and valve regulated lead-acid batteries. Both have their own advantages and shortcomings. In the process of selecting batteries, the actual needs of electric locomotives should be taken into account, and the reasonable selection should be based on the use of two types of batteries in electric locomotives.

Comparison of the use of 2 cadmium nickel alkaline batteries and valve regulated lead-acid batteries in electric locomotives

2.1 Environmental temperature requirements for application

Electric locomotives have high requirements for batteries, not only requiring the battery to provide pantograph starting power for the locomotive at an ambient temperature of minus 40 degrees Celsius, but also requiring the battery to be able to charge normally at 40 degrees Celsius. For lead-acid batteries, the first requirement is to be able to discharge normally at minus 40 degrees Celsius. However, in order to charge normally under high temperature conditions, it is necessary to ensure good ventilation and heat dissipation conditions. Otherwise, problems such as bulging and damage may occur during the charging process. Ordinary cadmium nickel alkaline batteries can meet the relevant environmental temperature requirements, that is, they can discharge normally at minus 40 degrees Celsius, charge normally at an ambient temperature of above 55 degrees Celsius, and operate normally at an ambient temperature of minus 40 degrees Celsius to above 55 degrees Celsius. Moreover, they have high reliability and low failure rates in terms of bulging and damage.

2.2 Ability to withstand overcharging and overdischarging

Constant voltage current limiting charging is the primary charging method for electric locomotives to charge batteries, with a starting current of 50-80 amperes or more during the charging process. For lead-acid batteries, the requirements for charging and discharging current are relatively strict, and the allowed charging and discharging current is relatively small. In the case of long-term use of high current charging, it is easy for the battery to form bad luck, which can cause chronic damage. Compared to lead-acid batteries, cadmium nickel alkaline batteries have more advantages in resistance to overcharging and overdischarging, and have stronger resistance to high current charging and high current discharging. In addition, during the operation or maintenance of electric locomotives, there may be a simple situation of battery depletion. In this situation, lead-acid batteries are more easily damaged, while cadmium nickel alkaline batteries do not exhibit similar problems. Cadmium nickel alkaline batteries can recover and function normally even at zero voltage after several cycles. From this, it can be seen that cadmium nickel alkaline batteries have better resistance to overcharging and overdischarging than lead-acid batteries.

2.3 Anti short circuit and misconnection capabilities

Compared to lead-acid batteries, cadmium nickel alkaline batteries have more advantages in terms of resistance to short circuits and misconnections. The former may simply show damage in the event of a short circuit or misconnection, and may even cause a fire, resulting in huge losses and posing significant safety risks. For example, if a short circuit or misconnection causes a fire in a lead-acid battery, not only will the lead-acid battery itself be damaged, but adjacent electrical appliances will also be easily damaged. Even if the fire is not caused, the lead-acid battery itself will usually be damaged. Compared to lead-acid batteries, cadmium nickel alkaline batteries have higher safety and reliability. Even if there is a misconnection, they can be reused after capacity recovery and will not be directly scrapped or cause fires like lead-acid batteries. From this, it can be seen that cadmium nickel alkaline batteries have more advantages in terms of short-circuit resistance and misconnection ability.

2.4 Operation with defects is necessary

For lead-acid batteries, the dissolution precipitation mechanism is involved in the electrochemical reaction process, and the corrosion of the grid and pole is easily caused by the influence of the electrolyte. In addition, during the charging process of lead-acid batteries, the electrolyte may swell. If there is excessive thermal expansion, it will cause a certain battery to open circuit, and the entire battery group will be affected, thus losing its function and the battery cannot continue to operate. If the float voltage of one of the batteries exceeds 2.4 watts, it will cause all batteries to be damaged. Therefore, the faulty operation of lead-acid batteries is not strong, and compared to lead-acid batteries, cadmium nickel alkaline batteries have more advantages in this regard, without the related defects encountered by lead-acid batteries. Cadmium nickel alkaline batteries are used in electric locomotives. Even if a certain battery experiences a short circuit, the faulty battery can serve as a connecting line between the front and rear batteries. In addition, the floating voltage scale of cadmium nickel alkaline batteries is wide. Therefore, in the event of a short circuit in a certain battery, only one battery is missing from the entire battery pack, which can fully maintain the faulty operation. From this, it can be seen that in terms of faulty operation, cadmium nickel alkaline batteries are superior to lead-acid batteries.

2.5 Protection Requirements: The selection of electric locomotive batteries should fully consider protection requirements, because battery protection not only affects the operation of electric locomotives, but also involves certain protection costs. Reasonable selection of batteries can reduce the cost investment while reducing the impact of battery protection. For lead-acid batteries, they are free of fluid change for life. Cadmium nickel alkaline batteries require electrolyte replacement every 5-8 years and pure water addition every 2-3 years. The frequency of condition checks and capacity balancing for the two types of batteries is fundamentally the same. But compared to lead-acid batteries, cadmium nickel alkaline batteries have higher protection power.

At that time, the country attached great importance to environmental protection, so when selecting electric locomotive batteries, their environmental friendliness should also be fully considered. For lead-acid batteries, the diluted sulfuric acid in the electrolyte has a certain degree of corrosiveness, and the electrode lead is also classified as a toxic metal. Regarding cadmium nickel alkaline batteries, the dust generated during the production process of the negative electrode cadmium can cause certain damage to the human body, and the negative electrode cadmium can also threaten human nerves. From this, it can be seen that cadmium electrodes pose a threat to human health both in production and in use. Other cadmium nickel alkaline batteries use potassium hydroxide as the electrolyte, which is a strong base with strong corrosiveness. Therefore, both lead-acid batteries and cadmium nickel alkaline batteries have certain corrosiveness and pose a huge threat to human health. To avoid damage to the environment and human health caused by electric locomotive batteries, they should be disposed of in a standardized manner after their service life is over, such as recycling the electrodes of electric locomotive batteries, neutralizing the electrolyte of electric locomotive batteries, etc., to minimize the damage of electric locomotive batteries to the environment and human health. During the use of electric locomotive batteries, it is necessary to analyze whether the battery performance can meet the requirements of electric locomotives based on factors such as humidity, weight, and temperature. Compared to lead-acid batteries, cadmium nickel alkaline batteries have stronger temperature adaptability, better resistance to overcharging and overdischarging, resistance to short circuit misconnection, and ability to operate with faults. Moreover, they have lower investment costs. This fully indicates that cadmium nickel alkaline batteries have more advantages, with more ideal reliability, application, and safety.