Rechargeable batteries (also known as secondary batteries) have a wide range of applications. Since they are rechargeable and the devices they power are lighter, they have now replaced a large proportion of simple primary batteries in electrical appliances, fuel-powered motors, and corded electrical appliances. Rechargeable tools have become widely used in DIY and commercial applications. Hedge trimmers, tree saws, and lawn mowers can be found in home gardens. Rechargeable batteries have become indispensable in cell phones, laptops, and electric cars. In the future, the demand for battery storage for renewable energies, e.g., from private photovoltaic systems, will also increase.

In an accumulator, electrical energy is converted into chemical energy during charging. When a consumer is connected, the chemical energy is converted back into electrical energy. Accumulator types are named after the materials used. Well-known battery types include:

Lithium-ion batteries (mobile phones, notebooks, and cameras), nickel-metal hydride batteries (model making, electric cars), and lead-acid batteries (starter batteries for vehicles with combustion engines and stand-alone photovoltaic systems).

The advantages are obvious: lightweight devices enable quiet, emission-free operation without cable clutter. Unlike batteries, rechargeable batteries have higher acquisition costs, as you have to buy a suitable charger in addition to the power storage devices. But it's worth it, because rechargeable batteries can be recharged several times. Depending on the battery type, 500 to 10,000 charging cycles can be achieved. However, if the rechargeable batteries are not used, they lose a large part of their energy after just a few months. To prevent self-discharge, rechargeable batteries should be recharged after six months at the latest. It is best to always keep the battery level between 30–80% charge.

Unlike rechargeable batteries, batteries often retain their charge for years, provided that the power consumption of the devices is relatively low. Batteries are therefore preferably used for devices that need to function reliably for a long time, such as alarm clocks, watches, smoke detectors, remote controls, etc. These devices use very little power and the batteries used rarely need to be replaced. The use of rechargeable batteries would be unfavorable in this case, as they need to be recharged frequently.

The production of batteries and rechargeable batteries consumes between 40 and 500 times more energy than they subsequently provide during use. Electricity from batteries is around 300 times more expensive than electricity from the grid! With rechargeable batteries, the environmental and energy balance can be significantly improved through repeated recharging.

The production of rechargeable batteries requires finite raw materials (metal ores), which are often extracted through environmentally destructive mining practices. The most commonly produced lithium-ion batteries contain cobalt and lithium. The processing of cobalt produces toxic, heavy metal-containing slag as a residue, which poisons entire regions and people (mining in Congo, Zambia, or China). Lithium is extracted in a similar way to sea salt by drying the brine in artificial ponds. The lithium is found in underground watercourses and is exposed by blasting. In Chile, this use of groundwater promotes the drying out of the landscape. In other lithium-bearing ore deposits in Australia, Canada, and China, environmental pollution is caused by fine dust and massive water extraction during the drainage of lakes. You can find more information on raw material extraction in the list of links below.

With regard to environmental friendliness, it is all the more important that the recycling of rechargeable and non-rechargeable batteries ensures that the recovered metals are reused in battery production. The Battery Act (BattG) was amended on January 1, 2021, and is aimed at manufacturers, distributors, end users, and public waste disposal authorities, among others. It regulates the separate collection of used batteries and rechargeable batteries, free return, return systems, and recycling (for more information, see the list of links below).

Although electric cars, commercial vehicles, and e-bikes are on the rise, limited ranges, high prices, a cumbersome charging infrastructure, and raw material-intensive battery production are delaying a rapid shift to e-mobility. For widespread use, batteries must become even more powerful, durable, sustainable, and cost-effective. Solutions that use sodium-ion batteries, for example, to replace rare lithium salts with simple table salt are still in development.

Due to the serious environmental damage caused by the manufacture of batteries, consider what the best solution is when purchasing a new one.

Do not wait until your battery is completely discharged. It is better to recharge the battery early to extend its service life.

Typical actions that can damage the battery in the long term include storing the battery in a hot car or leaving the battery in the laptop when always working on mains power.

Many chargers consume power as long as they are plugged into the outlet, even when they are not charging. Therefore, disconnect chargers from the power supply after charging or use chargers that automatically disconnect from the power supply. The same applies to power supplies.

Some manufacturers offer solar-powered chargers. These allow you to charge your batteries in an environmentally friendly way using solar energy, without having to rely on mains power sockets.

Lithium-containing batteries and rechargeable batteries pose a fire hazard! Caution is advised if your cell phone battery swells. Incorrect disposal in particular can lead to internal and external short circuits due to thermal effects or mechanical damage. A short circuit can lead to fire or explosion. To prevent a short circuit, cover the poles of discarded lithium-ion batteries with adhesive tape. Wash your hands thoroughly after direct contact with leaking batteries.

Never mix up the battery terminals. This can permanently destroy the batteries. Only charge batteries that are suitable for the charger.

Used batteries and rechargeable batteries are hazardous waste. You are therefore obliged to collect them separately. This is also indicated on each battery by the symbol of a crossed-out trash can. They must not be disposed of in household waste—or carelessly discarded in the environment. Dispose of your used batteries and rechargeable batteries at specialist retailers, recycling centers, hazardous waste collection points, or the Mainz environmental store.