Rechargeable batteries vs disposable batteries: which are best?

Americans buy about 4 billion disposable batteries every year. That averages out to 47 batteries per household. Rechargeable batteries last about four years. So 12 rechargeable batteries that last that long can replace 188 disposable ones. 

Rechargeable batteries cost more to buy but much less in the long run. They are also the more eco-friendly choice. For one thing, it’s easier and more economical to recycle them once you can’t recharge them anymore. 

There are a few situations where disposable batteries work better than rechargeable batteries, but only a few. 

Rechargeable batteries have gotten better over the years. They didn’t use to work well in all kinds of equipment or hold a charge as long as alkaline batteries. Now, they do. What’s more, they’re sealed. They don’t leak the electrolyte and ruin your equipment as alkaline batteries can. 

How batteries work

All batteries comprise two electrodes separated by an electrolyte in some kind of case with two terminals: positive and negative. When operating anything from a flashlight to a car, electrons travel as an electric current from the negative terminal through the electrolyte to the positive terminal and from there to the device.

In the standard alkaline dry cell battery, current can flow in only one direction. When it becomes completely discharged, the battery must be discarded. 

A rechargeable battery allows an outside current to reverse the flow. It makes current flow from the positive terminal back to the negative terminal until the negative side has a fresh supply of electrons. 

Flashlights, remotes, radios, clocks, and many other devices run on AAA, AA, C, D, or 9-volt batteries. More often than not, devices require more than one cell to operate.

Rechargeable batteries in these sizes use nickel-metal hydride technology. Overcharging them can decrease their capacity. So a good charger ought to shut off when it has fully charged the batteries. 

Some small appliances use non-rechargeable button batteries, which are now mostly made with lithium. These include watches, hearing aids, calculators, and remotes for cars. 

The environmental impact of batteries

All batteries use contrasting metals for electrodes and harsh acids or bases for the electrolyte. The metals can include highly toxic cadmium, cobalt, nickel, and silver. Mining them has a harmful effect on the environment. The chemicals used for the electrolyte are hazards to the people who must work with them and hazards if released into the environment.  

Improper disposal of batteries after the end of their useful life presents health and safety risks, too. Quite beyond the toxic nature of some components, used batteries may still have enough energy to injure people or cause fires.

Formerly, standard single-use alkaline batteries contained mercury, which made them a hazardous waste. But in the US, anyway, mercury in dry cells was outlawed in 1996. Recycling them is possible but not considered economically feasible. Except in California, it is legal simply to throw them in the trash. But their metals and electrolytes still contribute to leachate in landfills. Legal or not, throwing them in the trash is a bad idea. 

When incinerated, batteries can release their metals into the atmosphere. The metals certainly accumulate in the ash

Lithium batteries require special handling, and not all of them are rechargeable. Some single-use lithium batteries look very much like common alkaline batteries, but the word “lithium” will be printed on them. Rechargeable or not, they can cause fires if their terminal ends touch. Therefore, place some kind of non-conductive tape over the terminals before disposal.  And that includes taking them or sending them to be recycled. 

Battery recycling

It’s possible but not economically feasible to recycle alkaline batteries. If you use a lot of them, you can recycle them with a mail-in program. Many stores that sell batteries offer free battery collection. Just check first to make sure they accept alkaline batteries. I have written elsewhere about how to find places to recycle dead batteries. 

Otherwise, it’s best to take them to your local hazardous household waste recycling center. Many places sponsor occasional events for collecting them. Some have year-round drop-off centers. 

It is easier and more economical to recycle rechargeable batteries than alkaline batteries. Just take them to free drop-off boxes  at retailers that sell a lot of batteries. Or deal with them as any other household hazardous waste. 

Here’s another reason to recycle rechargeable batteries: 

Some common battery components (including cadmium, lithium, and graphite) are considered critical minerals in the US. They are economically and strategically important but not easily obtainable from American sources. There are no easy substitutes for them.

Battery recycling facilities crush alkaline, zinc carbon, zinc air, and lithium-ion batteries with a hammer mill and place the fragments in a vat. Paper and plastic components rise to the top, where they are skimmed off. Heavy metals sink to the bottom. After further separation, each material goes through its own recycling stream. 

Materials recovered include zinc and manganese concentrate, cobalt and lithium salts, steel, copper, aluminum, paper, and plastic. 

Lithium batteries other than lithium-ion go through a shredder or high-speed hammer. The components are then submerged in a caustic solution that neutralizes the electrolyte. The entire process recovers lithium, ferrous metals, and carbon.  

Nickel metal hydride and nickel-cadmium batteries require high-temperature metal reclamation after separating plastics from metals. The various metals melt at different temperatures, enabling separation. 

Rechargeable batteries are better for your budget

Rechargeable batteries cost more initially than disposable batteries. Plus, you need to buy a charger. But after that, when a battery runs down, you don’t have to throw it out and put in another new battery. 

Suppose you need to replace 72 every year. And suppose you buy a charger and eight rechargeable batteries for $40. A year’s supply of disposable batteries may cost only $30, but at the end of five years, their total cost is $150. Your eight rechargeable batteries have lasted that long. You haven’t needed to buy any more, so your total cost for batteries is $40 plus a little extra on your electric bill. 

And so rechargeable batteries will almost always save you money over time. How much depends on how quickly you go through batteries. The more batteries you use, the more money rechargeable batteries will save for you. 

The few advantages of disposable batteries

Disposable alkaline batteries may be better for a few applications. Most manufacturers of smoke alarms recommend against using rechargeable batteries, for example. 

And disposables have an important advantage for emergency equipment you don’t expect to use very often: They retain their charge a lot longer. Just be aware of the expiration date. 

Backpackers and others who spend a lot of time away from electricity can always carry solar battery chargers. But they might find alkaline batteries handy for backup when there isn’t enough sunlight to operate them.  Plus, alkaline batteries have a more rugged chemistry than rechargeable ones. They can take rougher handling. 

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Sources:

Are rechargeable batteries better than alkaline? most of the time / Sarah Witman, New York Times. June 6, 2019
Battery recycling: facts, questions, and how-to tips / GA Anderson, TurboFuture. 2018
Battery recycling processes / Urbana, Illinois
How batteries work / Marshall Brain, Charles W. Bryant, and Clint Pumphrey, How Stuff Works. February 11, 2021
Rechargeable batteries: are they worth it? / Dallas Cox, Clark.com. August 24, 2020 
Used household batteries / US Environmental Protection Agency