Some Ways For Rapid Testing Automotive and Starter Batteries ...

Posted on | August 5, 2012 | Comments Off

Some Ways For Rapid Testing Automotive and Starter Batteries

Portable batteries for cell phones,laptops and cameras may be rapid-tested by applying a number of load pulses while observing the relationship between voltage and current.Ohm?s Law is used to calculate the internal resistance.Comparing the readings against a table of values estimates the battery?s state-of-health.This load pulse method does not work well for larger batteries and AC conductance is commonly used.An AC voltage is applied to the battery terminals that floats as a ripple on top of the battery?s DC voltage and charges and discharges the battery alternatively.

AC conductance has been incorporated into a number of hand-held testers to check batteries for vehicular and stationary batteries.To offer simple and low-cost units,these testers load the battery with pulses rather than injecting sinusoidal signals.The thermal voltage threshold of a lead-acid battery is 25mV per cell.AC conductance provides accurate readings,provided the primary battery is fully charged,has rested or has been briefly discharged prior to taking the reading.AC conductance tends to become unreliable on low charge and sometimes fails a good battery.At other times,a faulty battery may pass as good.The correlation to the battery?s state-of-charge is a common complaint by users.AC conductance works best in identifying batteries with definite deficiencies.

AC conductance is non-invasive,quick and the test instruments are relatively inexpensive.There are,however,some fundamental problems.

Most commercial testers use only one frequency,which is commonly below 100 Hertz.Multi-frequency systems would be more accurate but require complex data interpretation software and expensive hardware.In this paper we focus on Electrochemical Impedance Spectroscopy (EIS), a method that overcomes some of the shortcomings of AC conductance.

Electrochemical Impedance Spectroscopy (EIS)

EIS evaluates the electrochemical characteristics of a battery by applying an AC potential at varying frequencies and measuring the current response of the electrochemical cell.The frequency may vary from about 100 micro Hertz (Hz) to 100 kilo Hertz (kHz).100Hz is a very low frequency that takes more than two hours to complete one full cycle.In comparison,100kHz completes 100,000 cycles in one second.Applying various frequencies can be envisioned as going through different layers of the lithium battery and examining its characteristics at all levels.Battery resistance consists of three types,which are: pure resistance, inductance and capacitance.Figure 1 illustrates the classic Randles model,which represents a typical battery.

Capacitance is responsible for the capacitor effect; and the inductance is accountable for the so-called magnetic field,or coil effect.The voltage on a capacitor lags behind the current.On a magnetic coil,on the other hand,the current lags behind the voltage.When applying a sine wave to a battery,the reactive resistance produces a phase shift between voltage and current.This information is used to evaluate the battery.

EIS has been used for a number of years to perform in-flight analysis of satellite batteries,as well as estimating grid corrosion and water loss on aviation and stationary batteries.EIS gives the ability to observe the kinetic reaction of the electrodes and allows analyzing changes of analyze changes that occur in everyday battery usage.Increases in impedance readings hint at minute intrusion of corrosion and other deficiencies. Impedance studies using the EIS methods have been carried out on lead-acid,nickel-cadmium,nickel-metal-hydride and lithium-ion 18650 battery.Best results are obtained on a single cell.

Modern technology can help by storing characteristic settings of a given battery type in the test instrument.Advanced digital signal processors are able to carry out millions of instructions per second.Software translates the data into a single reading.EIS has the potential of becoming a viable alternative to AC conductance in checking automotive,traction and stationary batteries.Noteworthy advancements are being made in his field.

Article From: http://www.batteryfaq.net/battery-technology/some-ways-for-rapid-testing-automotive-and-starter-batteries-759.html

?

Dongguan Large Electronic Co., Ltd is always committed to serving industrial users, offering the most optimal battery solutions and supplying battery products.Welcome to visit:http://www.large-battery.com to buy the quality lithium battery and get the best 18650 battery.

Comments

Source: http://www.knightsforobama.org/298/some-ways-for-rapid-testing-automotive-and-starter-batteries

king jong il dead south korea baron davis duggar family gilbert arenas dexter dexter