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Rechargeable batteries are batteries with a reversible reaction such that their stored chemical energy can be fully restored through the application of electrical energy. They are also called storage batteries, secondary cells, and, in British usage, accumulators (whose abbreviation accu, or akku from the German akkumulator, has a more widespread use). Their designs and chemical formulations are widely varied to serve many diverse markets and uses. Some types of rechargeable batteries are susceptible to damage due to reverse charging if they are fully discharged; other types need to be fully discharged occasionally in order to maintain the capacity for deep discharge. There are fully integrated battery chargers, often called smart chargers, which regulate a safe charging voltage and current for each chemistry. Attempting to recharge non-rechargeable batteries (or storage batteries in an unsafe manner) may lead to a battery explosion.
A comparison of rechargable batteries[edit]
| Battery name | Cell Potential (V) | Description | Composition | Energy density (Wh/kg) | Development Status |
|---|---|---|---|---|---|
| Lead-acid battery | 2.1V | The major advantages of a lead-acid battery are its low cost and ability to produce high surge currents. Although this battery chemistry has much lower energy density than many of the other chemistries available today, it is still the most common battery used in conventional automobiles. There are predominantly three varieties: with entirely wet cells (as it was originally constructed), with a gelled electrolyte, and with the electrolyte absorbed into a glass mat. The latter two are sealed with valve regulation to prevent spills and the resultant corrosion, while still allowing for the release of hydrogen and oxygen gasses if it is improperly used. | cathode: Lead (IV) oxide (PbO2) anode: Lead (Pb) |
30-40 | Invented 1859 |
| Nickel-iron battery | 1.2V | Nickel-iron batteries are very robust and tolerant of abuse, withstanding overcharging, overdischarging, short-circuiting and thermal shocks while maintaining an exceptionally long life. Often used in backup situations, they can be continuously charged and last for 20 years. They are limited by a low specific energy, poor charge retention, poor low-temperature performance and a low energy-to-weight ratio. These limitations, combined with its high cost of manufacture compared with the lead-acid battery, contribute to its sparse usage today. | cathode: Nickel(III) oxide-hydroxide (NiOOH) anode: Iron (Pb) |
~50 | Produced from 1903 |
| Battery type | Description | Composition | Energy density (MJ/kg) |
Applications | Development status |
|---|---|---|---|---|---|
| Nickel cadmium battery | This chemistry gives the longest cycle life (over 1500 cycles), but has low energy density compared to some of the other chemistries. Batteries using older technology suffer from memory effect, but this has been reduced drastically in modern batteries. Cadmium is toxic to most life forms, so poses environmental concerns. | anode: cadmium cathode: nickel |
Used in many domestic applications, but being superseded by Li-ion and Ni-MH types | Mass produced from 1946 | |
| Nickel metal hydride battery | similar to a nickel-cadmium (NiCd) battery but has a hydride absorbing alloy for the anode instead of cadmium; therefore, it is less detrimental to the environment. A NiMH battery can have two to three times the capacity of an equivalent size NiCd and the memory effect is not as significant. However, compared to the lithium ion chemistry, the volumetric energy density is lower and self-discharge is higher. | anode: hydride absorbing alloy cathode: nickel |
0.22 | hybrid vehicles such as the Toyota Prius and consumer electronics | Made available 1983 |
| Lithium ion battery | a relatively modern battery chemistry that offers a very high charge density (i.e. a light battery will store a lot of energy) and which does not suffer from any memory effect whatsoever. | 0.54 to 0.72 | Laptops, modern camera phones, some rechargeable MP3 players and most other portable rechargeable digital equipment | Released c1990 | |
| Lithium ion polymer battery | similar characteristics to lithium-ion, but with slightly less charge density and a greater life cycle degradation rate. | ultra-thin (1 mm thick) cells for the latest PDAs | Released 1996 | ||
| Aluminium battery | potentially twenty times the energy density of the best currently available rechargable batteries. | In research stage | |||
| NaS battery | exhibits a high energy density, high efficiency of charge/discharge (89—92%), long cycle life, and is made from inexpensive, non-toxic materials. However, the operating temperature of 300 to 350 °C and the highly corrosive nature of sodium make it suitable only for large-scale non-mobile applications. | A suggested application is grid energy storage in the electric grid | |||
| Nickel-zinc battery | are a type of rechargeable battery commonly used in the light electric vehicle sector. The battery is still not commonly found in the mass market, but they are considered as the next generation batteries used for high drain applications, and is expected to replace lead-acid batteries because of their higher energy to mass ratio and higher power to mass ratio (up to 75% lighter for the same power), and are cheap compared to nickel-cadmium batteries (expected to be priced somewhere in between NiCd and lead-acids, but have twice the energy storing capacity). | ||||
| Molten salt battery | high temperature electric battery that offers both a higher energy density through the proper selection of reactant pairs as well as a higher power density by means of a high conductivity molten salt electrolyte. They are used in services where high energy density and high power density are required. These features make rechargeable molten salt batteries the most promising batteries for powering electric vehicles. Operating temperatures of 400 to 700°C however brings problems of thermal management and safety and places more stringent requirements on the rest of the battery components. | molten salt electrolyte | |||
| Super iron battery | a new class of rechargeable electric battery. "Super-iron" is a moniker for a special kind of ferrate salt (iron(VI)): potassium ferrate or barium ferrate, as used in this new class of batteries.[1] As of 2004, chemist Stuart Licht of the University of Massachusetts in Boston was leading research into a Super-iron battery. | In research stage | |||
| Zinc bromide battery | a type of hybrid flow battery. A solution of zinc bromide is stored in two tanks. When the battery is charged or discharged the solutions (electrolytes) are pumped through a reactor and back into the tanks. One tank is used to store the electrolyte for the positive electrode reactions and the other for the negative. | zinc bromide electrolyte |
Recharging[edit]
The energy used to recharge rechargeable batteries mostly comes from mains electricity using an adapter unit. Recharging from solar panels is also attractive. Recharging from the 12V battery of a car is also possible. Use of a hand generator is also possible, but it is not clear if such devices are commercially made.
For uses like radios and torches, rechargeable batteries may be replaced by clockwork mechanisms or dynamos.
Reverse charging[edit]
Reverse charging is when a rechargeable battery is recharged with its polarity reversed. Reverse charging can occur under a number of circumstances. The two most important being:
- When a battery is incorrectly inserted into a charger
- When multiple batteries are used in series in a device. When one battery completely discharges ahead of the rest, the other batteries in series may force the discharged battery to discharge to below zero voltage.
Reverse charging may lead to explosion, leakage, damage to the battery and/or to the device or charger. Old and new batteries and batteries of varying types or brands should not be mixed in the same circuit.
See also[edit]
- Battery pack
- Battery Resources
- Fuel cell
- Mercury-containing and Rechargeable Battery Management Act
- Trickle charging
External links[edit]
- Rechargeable Batteries Guide
- Battery University
- Batteries in a Portable World
- HowStuffWorks.com's Battery Article
- Scientific American's Battery Article