Differences Between Alkaline & NiMH Rechargeable Batteries

By Andrew Copley

Are batteries really different?
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A variety of batteries are available on the market. This leaves many people confused over which battery to use. Its more than just a matter of whether they're disposable or rechargeable, it's what can give the best usage. Alkaline and NiMH each have their own advantages and disadvantages.


"AA" alkaline batteries produce 1.5 volts electrical charge at a rate of 2,400 milli-amp-hours. Think of it as pouring a 1.5-oz. cup of coffee 2,400 times in one hour. Most alkalines are not rechargeable but have a slow discharge rate. NiMH batteries are rechargeable, but the discharge rate is 25 percent a month. Volts are 1.2 with a rate up to 2,900 mAh. The difference in power is subtle. Alkaline is good for low power devices, NiMH is good for high power devices.


Alkaline batteries are good for using in remote controls, flashlights, tape or CD players and clocks -- items that are not continually used or don't draw a lot of power to function. In these devices the alkaline battery will last for a long time. High power consumption devices like digital cameras, handheld GPS units, PDAs and anything that has backlighting on a screen needs NiMH batteries.

Life Expectancy

Single use alkaline batteries can last for a year or more, depending on the device they're powering. Some rechargeable alkaline batteries can last for several uses but with each recharge they lose a portion of thier capacity. Depending on the device you use it in, a NiMH battery can last for years because you can recharge them 100 times or more.

Power Consumption

Alkaline batteries lose their charge steadily. As you use the battery the voltage and amperage go down until the device starts working slower and finally dies. NiMH batteries tend to keep the voltage and amperage at the same level. The power drops only when there is almost zero charge left in the battery. This gives a more steady flow of energy to the device but little warning of when the power will die.