Information on the discharge of nickel-metal hydride batteries

Discharge is the process of output current to the external circuit. In the process of discharge, nickel-metal hydride batteries are accompanied by voltage drop and capacity decrease.

The performance of nickel-metal hydride power batteries is assessed by the ratio of output power to input power, and it can also be roughly converted into the ratio of output capacity to input capacity. The total output power of the nickel-metal hydride battery used in the correct method can normally reach more than 95 % of the input power. The difference in the discharge effect is due to the internal and external resistance and discharge characteristics of the battery at different currents and temperatures. There will be certain differences.

Experiments show that the discharge efficiency of nickel-metal hydride batteries is obviously affected by current and temperature:

1, nickel-metal hydride batteries have good low-temperature discharge characteristics, in this respect even better than lithium batteries, even at -20 °C ambient temperature, using a large current (at 1C discharge rate) discharge, the amount of electricity released can reach the nominal capacity 85 % or more. The capacity loss in high temperature environments above 40 °C may reach 5 to 10 %. Although nickel-metal hydride batteries have good low-temperature discharge characteristics, their operating temperature is still appropriate between 0 and 40 °C. After all, after this temperature range, the battery capacity will be reduced to varying degrees.

2, according to IEC standards, nickel-metal hydride battery capacity is calculated using standard charging and discharging, in this standard calculation the applicable current is 0.2 C. In fact, discharge at a small current of 0.2 C is more than 10 % more than the capacity of discharge with 1C.

If the above two standards are not properly applied, the battery discharge time will be reduced. For example, in the above low temperature environment, only 85 % of the electricity will be emitted, and the large current will also reduce the discharge efficiency, thus shortening the discharge time. Of course, if the battery discharge time is significantly too short under normal operating conditions, it is necessary to check whether the battery is not fully charged, which is traced back to the issue of nickel-metal hydride battery charging.

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