State of charge

State of charge

State of charge (SOC) is the equivalent of a fuel gauge for the battery pack in a battery electric vehicle (BEV), hybrid vehicle (HEV), or plug-in hybrid electric vehicle (PHEV). The units of SOC are percent points (0% = empty; 100% = full).

Determining SOC

SOC cannot usually be determined directly.In general there are four methods to determine SOC indirectly:
* Chemical
* Voltage
* Current Integration
* Pressure

Chemical method

This method works only with batteries that offer access to their liquid electrolyte, such as non-sealed Lead Acid batteries. The Specific Gravity or pH of the electrolyte can be used to indicate the SOC of the battery.

Voltage method

This method converts a reading of the battery voltage to SOC, using the known discharge curve (voltage vs. SOC) of the battery. However, the voltage is more significantly affected by the battery current (due to the battery's internal resistance) and temperature. Therefore, this method can be made more accurate by compensating the voltage reading by a correction term proportional to the battery current, and by using a look-up table of battery's Open Circuit Voltage vs. Temperature.

Current Integration method

This method (a.k.a.: "Coulomb counting") calculates the SOC as the integral of the battery current. Like all real life integrals, this method suffers from long term drift, and lack of a reference point. Therefore, the SOC must be calibrated on a regular basis, such as by resetting the SOC to 100 % when a charger determines that the battery is fully charged (using one of the other 3 methods described here.

Pressure method

This method can be used with certain NiMH batteries, whose internal pressure increases rapidly when the battery is charged. More commonly, a pressure switch indicates if the battery is fully charged. This method may be improved by taking into account Peukert's law which is a function of charge/discharge rate or ampere.

See also

* Battery balancer
* Battery monitoring
* Battery charger
* Depth Of Discharge (DOD)


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • state of charge — See battery charge …   Dictionary of automotive terms

  • State of charge — (SOC)   The available capacity remaining in the battery, expressed as a percentage of the rated capacity.   Solar Electric Glossary …   Energy terms

  • Charge ordering — (CO) is a (first or second order) phase transition occurring mostly in strongly correlated materials such as transition metal oxides or organic conductors. Due to the strong interaction, the charge is localized on different sites leading to a… …   Wikipedia

  • Charge-sustaining — is the mode of operation utilized to manage Battery packs in conventional hybrid vehicles. State of charge (SOC) will fluctuate with driving conditions, but a target SOC is usually around 50 to 60 percent. Discharge patterns consist of many… …   Wikipedia

  • Charge-depleting — or EV mode refers to a mode of vehicle operation that is dependent on energy from the battery pack. Battery electric vehicles operate solely in this mode. Most plug in hybrids operate in charge depleting mode at startup, and switch to charge… …   Wikipedia

  • charge — [1] The action of passing an electric current through a battery to restore it to the active (charged) state. Normally the vehicle s generator or alternator takes care of this. If the vehicle is not used much, an external charger is needed to… …   Dictionary of automotive terms

  • charge controller —   An electronic device which regulates the voltage applied to the battery system from the PV array. Essential for ensuring that batteries obtain maximum state of charge and longest life.   Solar Electric Glossary …   Energy terms

  • State of New York —     State of New York     † Catholic Encyclopedia ► State of New York     One of the thirteen colonies of Great Britain, which on 4 July, 1776, adopted the Declaration of Independence and became the United States of America.     BOUNDARIES AND… …   Catholic encyclopedia

  • State of Washington —     State of Washington     † Catholic Encyclopedia ► State of Washington     One of the Pacific cost states, popularly known as the Evergreen State , the sixteenth in size among the state of the Union and the twenty ninth in the order of… …   Catholic encyclopedia

  • State and Church — • The Church and the State are both perfect societies, that is to say, each essentially aiming at a common good commensurate with the need of mankind at large and ultimate in a generic kind of life, and each juridically competent to provide all… …   Catholic encyclopedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”