Battery charger
Chargers may elevate the output voltage proportionally with current to compensate for impedance in the wires.
[3] A trickle charger provides a relatively small amount of current, only enough to counteract self-discharge of a battery that is idle for a long time.
For public access, installation of such chargers and the distribution support for them is an issue in the proposed adoption of electric cars.
[8] Battery cells which have been built to allow higher C-rates than usual must make provision for increased heating.
But high C-ratings are attractive to end users because such batteries can be charged more quickly, and produce higher current output in use.
High C-rates typically require the charger to carefully monitor battery parameters such as terminal voltage and temperature to prevent overcharging and so damage to the cells.
[9] For example, an automobile SLI (starting, lighting, ignition) lead–acid battery carries several risks of explosion.
Even so, many batteries left on a simple charger for too long will be weakened or destroyed due to over-charging.
The control circuitry can be built into the battery (generally for each cell) or in the external charging unit, or split between both.
The first stage is referred to as "bulk absorption"; the charging current is held high and constant and is limited by the capacity of the charger.
After that, the voltage decreases because of increasing temperature, which indicates to an intelligent charger that the battery is fully charged.
[11] Several companies have begun making devices that charge batteries using energy from human motion, such as walking.
An example, made by Tremont Electric, consists of a magnet held between two springs that can charge a battery as the device is moved up and down.
[12] A pedal-powered charger for mobile phones fitted into desks has been created for installation in public spaces, such as airports, railway stations and universities.
These are often connected to the electrical grid via control and interface circuits, whereas portable solar chargers are used off-grid (i.e. cars, boats, or RVs).
Although portable solar chargers obtain energy only from the sun, they can charge in low light like at sunset.
Timer based chargers also had the drawback that charging batteries that were not fully discharged would result in over-charging.
For instance, most Li-ion batteries cannot be safely trickle charged and can cause a fire or explosion.
The best are universal (i.e. can charge all battery types), and include automatic capacity testing and analyzing functions.
Products based on this approach include chargers for cellular phones, portable digital audio players, and tablet computers.
Public EV charging stations often provide 6 kW (host power of 208 to 240 V AC off a 40-ampere circuit).
[21] Onboard EV chargers (change AC power to DC power to recharge the EV's pack) can be: Power-factor correction (PFC) chargers can more closely approach the maximum current the plug can deliver, shortening charging time.
Project Better Place was deploying a network of charging stations and subsidizing vehicle battery costs through leases and credits until filing for bankruptcy in May 2013.
Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed an electric transport system, called Online Electric Vehicle (OLEV), where the vehicles get their power needs from cables underneath the surface of the road via inductive charging, a power source is placed underneath the road surface and power is wirelessly picked up on the vehicle itself.
Some higher-end models feature multiple ports are equipped with a display which indicates output current.
[25] In June 2009, 10 of the world's largest mobile phone manufacturers signed a Memorandum of Understanding to develop specifications for and support a microUSB-equipped common external power supply (EPS) for all data-enabled mobile phones sold in the EU.
[26] On October 22, 2009, the International Telecommunication Union announced that microUSB would be the standard for a universal charger for mobile handsets.
Chargers for stationary battery plants may have adequate voltage regulation and filtration and sufficient current capacity to allow the battery to be disconnected for maintenance, while the charger supplies the direct current (DC) system load.
The capacity of the charger is specified to maintain the system load and recharge a completely discharged battery within, say, 8 hours or other intervals.
Most modern cell phones, laptop and tablet computers, and most electric vehicles use lithium-ion batteries.
