Rechargeable battery
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Rechargeable batteries are batteries that can be restored to full charge by the application of electrical energy. They come in many different designs using different chemistry. They are also called storage battery, secondary cell or accu/akku (short for accumulator). Attempting to recharge non-rechargeable batteries may lead to a battery explosion. 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 exist fully integrated battery chargers that optimize the charging current.
List of batteries (in order of Wh/kg)
In the order of improving energy per weight ratios there are:
- Nickel-iron battery
- Gel battery - a type of lead-acid battery
- Lead-acid battery - commonly used in vehicles, alarm systems and uninterruptible power supplies. Used to be used as an "A" or "wet" battery in valve/vacuum tube radio sets. The major advantage of this chemistry is its low cost - a large battery (e.g. 70 Ah) is relatively cheap when compared to other chemistries. However, this battery chemistry has lower energy density than other battery chemistries available today.
- Nickel-cadmium battery - used in many domestic applications but being superseded by Li-Ion and Ni-MH types. This chemistry gives the longest cycle life (over 1500 cycles), but has low energy density compared to some of the other chemistries. Ni-Cd cells using older technology suffer from memory effect, but this has been reduced drastically in modern batteries.
- Nickel metal hydride battery
- 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. Used in laptops (notebook PCs), modern camera phones, some rechargeable MP3 players and most other portable rechargeable digital equipment.
- Lithium ion polymer battery - similar characteristics to lithium-ion, but with slightly less charge density and a greater life cycle degradation rate. This battery chemistry can be used for any battery to suit the manufacturer's needs, such as ultra-thin (1 mm thick) cells for the latest PDAs.
- Absorbed glass mat - another type of lead-acid battery
- NaS battery
- Sodium-metal chloride battery
- Nickel-zinc battery
- Molten salt battery
Recharging
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
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.
See also
- Fuel cell
- Trickle charging
- Zinc bromide battery
- Battery pack
- Mercury-containing and Rechargeable Battery Management Act
External links
- [Battery University]
- [Batteries in a Portable World]
- [HowStuffWorks.com's Battery Article]
- [Scientific American's Battery Article]
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