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Many modern gadgets use lithium ion batteries now but there are many other devices that aren’t suited for this type of power. Some still have compartments that you must pop open and slide in batteries you bought yourself.
Let’s say you need an AAA battery. Do you grab a disposable one or do you get one that you can recharge? For that matter, why can’t you recharge all of them? What’s the difference? That, turns out, is a matter of science and cost.
How Batteries Work
Batteries each have a positive terminal and a negative terminal. The positive terminal connects to a cathode and the negative connects to an anode. The cathode and anode are both known as electrodes. They occupy most of the battery, and it’s here where chemical reactions occur.
These electrochemical reactions are what produce the electricity that power your device. A separator prevents the cathode and the anode from touching — because bad things would happen if they did — but this separator doesn’t stop the flow of electricity once the terminal circuit is complete.
Batteries work via a combination of oxidation and reduction. The anode oxidizes, meaning it loses electrons. At the same time, the cathode absorbs electrons in a process called reduction. This only happens when a load completes a circuit between the two terminals. This load is your device.
Why Aren’t All Batteries Rechargeable?
Disposable batteries are all alkaline batteries, which means the cathode is made of manganese oxide and the anode is a zinc powder. The electrolyte is potassium hydroxide (i.e. the alkaline part). Eventually the energy-producing reaction corrodes the anode, preventing further reactions. At this point, the battery is dead.
Rechargeable batteries come in a variety of forms. The ones we see in laptops and smartphones are lithium ion. These use lithium cobalt oxide as the cathode and carbon as the anode. Unlike disposables, you can get electrons back from the cathode to the anode by introducing electricity (i.e. plugging the battery into an external power source).
But these aren’t the kind of rechargeable batteries that you can use in place of disposables.
Instead, you might use nickel-cadmium batteries (NiCd). Nickel is the cathode and cadmium is the anode. The recharge process isn’t perfect though, so these batteries lose total charge capacity after hundreds of recharge cycles. Fortunately, some newer options can sustain a strong charge through thousands of recharges.
These days, you’re more likely to see nickel-metal hydride batteries (NiMH), which have a significantly slower discharge rate than nickel-cadmium batteries. After a year on the shelf, they still have most of their charge. They also have 2x–3x the total charge capacity.
Why aren’t all batteries rechargeable? It comes down to a matter of cost. The materials used in disposable batteries are cheaper, and because they work so well in devices that only require tiny amounts of power (e.g. flashlights and LED candles), it remains cost effective to produce them. Lithium ion batteries are more expensive to produce, but they produce a lot of power. Nickel-cadmium and nickel-metal hydride batteries are somewhere in the middle.
Which Type Should You Use?
It depends on your needs, your budget, and your values.
Disposable batteries have a significantly cheaper upfront cost than rechargeable. Let’s say you need batteries for several flashlights, a digital camera, game controllers, radios, smoke alarms, and thermostats. Buying that many rechargeable batteries at once can run you over $100. Alternatively, you can spend less than $10 getting a bunch of cheap disposables from the dollar store.
On the flip side, those cheaper disposables won’t last all that long, even compared to other disposables. And no matter which brand you buy, the time will always come when you need to buy more. All of these devices draw different amounts of power, so some will last a year while others will burn out before the week is up — but they all die sooner or later.
For those devices that draw power a bit faster, such as digital cameras or game controllers, you should prefer rechargeable. This way you can continue using the same $30 pack of batteries for many years rather than buying a large $10 pack of disposables several times per year.
If you want to consume less of the world’s resources, then you should go the rechargeable route. This way you can use ten batteries over the course of a few years rather than hundreds of disposables. Making that change reduces how many minerals have to be mined to produce more batteries, and it lowers the number that eventually end up in a landfill.
Do Brand Names Make a Difference?
For rechargeable batteries, yes.
Most battery manufacturers use similar technologies, but their batteries have varying capacities. That means some need to be recharged more often than others. Some will also last for more cycles, which means you don’t have to replace them as often.
Duracell, Energizer, Panasonic, and Sony all make rechargeable batteries. You can even find store-branded options such as the Ikea LADDA. Panasonic Eneloop (previously Sanyo Eneloop) is on the expensive end, but some reviews show it at the top of the pack. Naturally, there are varying opinions out there. The Wirecutter recommends Energizer.
What Kind of Batteries Do You Use?
Rechargeable batteries have come a long way. Over the past few decades, batteries cost less and last longer. That means even if you’ve decided to stick with disposables in the past, now might be a good time to revisit the question. And if you’re checking out rechargeables for the first time, you will be spared some of the drawbacks that early adopters faced.
How would you describe your battery usage? Have you been a long-time fan of rechargeables? Do you find disposables more convenient? Are you thinking of switching? Let us know!