Primary batteries are batteries that cannot be recharged while secondary batteries are those which are rechargeable.

Primary batteries are highly important in situations where charging is impractical or impossible, such as in military combat and rescue missions. Primary batteries are employed in pacemakers, tire pressure gauges in vehicles, cameras, and wristwatches.

Primary batteries have high specific energy and can be used instantly. Primary batteries also possess considerable low self-discharge as compare to secondary batteries. The most popular primary battery, the alkaline battery, can be stored for up to 10 years and can also be carried on an aircraft without subject to UN and other transport regulations. When we look at rechargeable batteries, lead-acid battery has one of the lowest self-discharge rates and loses about 5% per month.

Primary batteries can only handle low discharge currents properly as they have high internal resistance. While most secondary batteries are rated at a 1C discharge current, the capacity on consumer-grade primary batteries is measured with a very low current of 25mA. Hence, secondary batteries outshine primary batteries when current requirements are high, and adequate power delivery is required.

Secondary batteries are suitable for applications like street lighting, electric cars, hybrid inverters, and mobile phones.