What is the difference in rated voltage between rechargeable NiMH batteries and disposable alkaline batteries?

2025-09-10 10:35:43

Rechargeable NiMH batteries typically have a rated voltage of 1.2V, which is determined by their nickel-metal hydride chemistry. The positive electrode of a NiMH battery uses nickel hydroxide, and the negative electrode uses a hydrogen storage alloy. During the charge and discharge process, hydrogen ions migrate between the positive and negative electrodes, generating a stable voltage plateau of 1.2V. This voltage is slightly lower than that of disposable alkaline batteries, but NiMH batteries can be used for a long time through cyclic charge and discharge.

Disposable alkaline batteries have a rated voltage of 1.5V due to their zinc-manganese redox reaction. The positive electrode of an Alkaline Battery is manganese dioxide, the negative electrode is zinc, and the electrolyte is potassium hydroxide solution. During the reaction, zinc is oxidized, releasing electrons, and manganese dioxide is reduced, accepting electrons, resulting in a stable 1.5V output voltage. This voltage characteristic allows the battery to deliver higher initial energy in a single charge.

This voltage difference directly affects device compatibility. The 1.2V voltage of nickel-metal hydride batteries is more stable during continuous discharge, making them suitable for devices requiring long-term power (such as remote controls and toys). Alkaline batteries, on the other hand, have a higher initial voltage of 1.5V, making them suitable for high-power, transient scenarios (such as camera flashes). However, it's important to note that if a device is designed solely for alkaline battery voltage, using nickel-metal hydride batteries may result in startup difficulties or performance degradation.

The voltage characteristics of the two battery types also reflect their technical positioning. Ni-metal hydride batteries achieve reversible charge and discharge capabilities by reducing voltage, extending their lifespan. Alkaline batteries achieve high single-shot energy output at a higher voltage, but they must be disposed of after use. Users should carefully consider the device's needs, frequency of use, and environmental requirements when making their choice.