What are the types of nickel-metal hydride battery activation

Nickel-metal hydride battery activation is divided into two types: one is the new battery capacity activation, and the other is the old battery internal resistance activation.

There are many discussions on the activation of new power cells. First of all, it must be clear that the purpose of new battery activation is to activate battery activity by activating active factors in the battery. The reason is that the self-discharge of nickel-metal hydride batteries is relatively large, and the amount of electricity in the long-term transit process will gradually lose, so that the battery activity will be reduced and it will enter a dormant state if it is not fully charged and discharged several times, because of the memory effect of nickel-metal hydride batteries. The output capacity is not up to the nominal capacity.

In terms of specific practices, it is usually performed 3 times fully charged and discharged, in which the charging mode is preferred to 0.1 C. This is because when the battery is not active and the charge is low, a large current charging will cause damage to the electrode. Theoretically, if the battery charge is greater than 40 % for the first charge(the manufacturer is generally described according to the factory date), it can be used first and then charged. Conversely, if it is less than 40 %, it can be used first and then used later. In practical applications, the newly produced batteries have instructions for use, which can be operated according to the manufacturer's guidance. Full capacity compliance may require at least 3 full charges, and some are required to be up to 5 times, because the amount of electricity that can be used after the first charge may be only 1/3 of the nominal capacity.

After the old nickel-metal hydride battery is used for a long period of time, the capacity will decrease. At the same time, the internal electrode that affects the effective output of the capacity will increase the resistance of the battery by producing an oxide layer. The decrease in capacity is irreversible. Therefore, reducing the internal resistance of the battery is the key to activating the old nickel-metal hydride battery. Otherwise, the old nickel-metal hydride battery will be increasingly unable to adapt to electric appliances that start large currents.

This kind of nickel-metal hydride battery with elevated internal resistance can be activated by high current discharge, and short-circuit tests are usually performed in practice. In the short circuit, the current will increase from small to large, and the nickel-metal hydride battery will slowly heat up. When the battery body reaches 40 °C, it will stop discharging, and the temperature will return to normal, short-circuit discharge again, and through this cycle, the short-circuit discharge process is completed until the battery voltage drops to 1.0 V. Some nickel-metal hydride batteries with low internal resistance may be used normally after a single discharge, so there is no need for a circular short circuit.

It should be pointed out that the purpose of activating new and old nickel-metal hydride batteries is not the same, so that short-circuit experiments must not be used for new battery activation.

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