Are There Advantages to Primary Batteries?
Primary batteries, which are batteries designed to be used once and then thrown away, don’t tend to get as much attention as secondary (i.e. rechargeable) batteries.
That might simply be because they are older and less likely to generate headlines. Primary batteries have been around in some form for over a hundred years, while rechargeable battery cells represent a much newer and more constantly-evolving technology.
When you do hear about primary batteries—also referred to as single-use, non-rechargeable or disposable batteries—it’s usually in the context of how they are inferior to secondary batteries. Today, primary batteries are more often discussed for their disadvantages than their advantages.
But there are advantages to primary batteries, and there are plenty of situations in which they are a better option than rechargeables.
Types of Primary Batteries
Similar to rechargeable batteries, primary batteries are often discussed as a broad category, but they are not a monolith. There are actually several types of primary batteries, and chances are you’ve encountered at least these three at some point:
Alkaline Batteries
Currently the most common primary batteries, alkaline batteries have been around since 1959, and have been the most widely used type of household battery since the early 80s. They create direct current through an electrochemical reaction between zinc and manganese dioxide in the presence of potassium hydroxide, which is an alkaline electrolyte (hence the name “alkaline battery”).
Zinc-Carbon Batteries
A very traditional type of primary battery, zinc-carbon batteries have been around in one form or another since the 19th century. Direct current is produced inside the battery from an electrochemical reaction between zinc and manganese dioxide. The battery also includes a carbon rod surrounded by the cathode, which gives the battery half of its name. Though they are still available, zinc-carbon batteries have largely been supplanted by the more efficient alkaline battery.
Lithium-Metal Batteries
There are actually several types of lithium-based primary battery cells, but they are often collectively referred to as lithium-metal batteries, or simply lithium batteries. Not to be confused with lithium-ion batteries, which are rechargeable, lithium-metal batteries contain a carbon cathode and a metallic lithium anode. These are among the most modern and efficient primary batteries.
Advantages of Primary Batteries
Primary batteries have a leg up on secondary batteries in many respects. Some of the most noteworthy advantages of primary batteries include:
Convenience
Primary batteries are the most widely and readily available batteries on earth. You can get them just about anywhere in a wide variety of commonly-used sizes, and you can purchase them with the knowledge that they will be immediately ready to use right out of the packaging, with no charging or other preparation required. And when they run out, you can simply dispose of your old batteries and get new ones. It doesn’t get much easier!
Cost Effectiveness
Although rechargeable batteries can be more economical in the long run due to the fact that they can be recharged and reused hundreds of times, primary batteries have a lower upfront cost per battery. Alkaline and carbon-zinc batteries are especially affordable. Ultimately, which type of battery you should get depends on what you need it for, but the low cost of primary batteries in the short term makes them an economical option.
Higher Specific Energy
Specific energy is one way to think of a battery’s capacity; it essentially refers to the amount of energy a battery contains in comparison to its mass. Without exception, primary batteries have higher specific energy than secondary batteries, with lithium-metal leading the pack at around 400 Wh/kg, followed by alkaline batteries at around 200 Wh/kg.
Low Self Discharge
The self-discharge rate of a battery refers to the rate at which a battery loses power when not in use. All batteries self-discharge to a degree, regardless of whether they are in a device or still in their packaging, but the rate varies quite a bit. While secondary batteries have the advantage of being rechargeable, primary batteries have a lower self-discharge rate.
Lithium-metal batteries self-discharge the slowest, and have a shelf life of 10 years or more, compared to about 5 to 7 years for alkaline batteries and around 2 years for zinc-carbon batteries. Rechargeable lithium-ion batteries, for comparison, self-discharge at a rate of about 2% to 3% per month.
Best Uses for Primary Batteries
Primary batteries are best used in low-drain devices, and in devices that are only occasionally used. They are also well-suited to long term storage.
While primary alkaline and lithium-metal batteries have a higher capacity in terms of specific energy than secondary batteries, they become drained more quickly than rechargeable batteries in high-drain devices like digital cameras and portable flashes. They may also be less than ideal for devices that require prolonged or continuous use, such as GPS receivers.
But primary batteries will outlast secondary batteries in low-drain devices like remotes, smoke detectors, LED headlamps and flashlights. Their low discharge rate also makes them the perfect choice for devices that are stowed away for later use, such as a flashlight that you keep in the glove compartment of your car.
It’s also a good idea to get primary batteries (especially lithium-metal) for disaster supplies and emergency-preparedness kits because their low rate of self-discharge gives them the best shelf life of any battery. That being the case, you can rest assured that they’ll be ready to use when you need them.
Are There Disadvantages of Primary Batteries?
No single type of battery is ideal for every situation, so it’s safe to say that there are both pros and cons to any type of battery you might choose to buy. With primary batteries, there are some disadvantages to consider.
Though a single primary battery costs less than a rechargeable secondary battery, rechargeable batteries are more economical over the long haul, especially if you use them in high-drain devices that eat up batteries quickly.
In a “big picture” sense, primary batteries are also less efficient because they contain far less energy than it takes to manufacture them. They also end up in landfills in vast quantities every year, making them a less environmentally conscious choice than rechargeable batteries.
Ultimately, it’s best to have several different types of battery on hand at any given time. That way, you can always choose the right battery for the right application.