Main performance parameters of the battery–four
The Charge and discharge rate
There are two expressions :the rate and the ratio. Rate is the time that charge and discharge time shows, that the charge-discharge rate is numerically equal to the battery's rated capacity (ampere-hour) divided by the provisions of the charge and discharge current (security) obtained the number of hours. Rate charge and discharge rate is another notation, the reciprocal is its value too. The original battery discharge rate is discharged through a fixed resistor to the termination voltage is the time to express. Discharge rate has the greater impact on battery performance.
Impedance
The battery has the great Electrode - electrolyte interface area, it can be equivalent to a large capacitor battery and the small resistor, inductor series circuit. But the reality is much more complicated, in particular, the impedance of the battery and the DC level over time change, the measured impedance is only valid for specific measurement of the state.
Main performance parameters of the battery–three
Open circuit voltage
Battery terminal voltage under open circuit condition is known as the open circuit voltage. The battery open circuit voltage is equal to the difference of the battery positive electrode potential and the anode electrode potential when the battery is in the circuit (ie when there is no current through the poles).the Open circuit voltage is marked by V, ie V open = Ф +-Ф-, which Ф +, Ф-are positive cells and negative electrode potential. Battery open circuit voltage generally is less than its emf. This is because the two poles of the battery electrolyte solution in the electrode potential is usually not balanced, but the stable electrode potential. Generally ,battery's open circuit voltage is similar to the battery EMF.
Internal resistance
Battery internal resistance is the resistance when the current through the battery internal gets. It includes the ohmic resistance and polarization resistance, polarization resistance also includes internal resistance of electrochemical polarization and concentration polarization resistance. Since the existence of internal resistance, battery voltage is always less than the battery emf <IMG src="http://t12.baidu.com/it/u=2325898283,3451946212&fm=0&gp=10.jpg" name=pn19> or the open circuit voltage. Battery internal resistance is not constant, in the charging and discharging process ,it changes over time (getting larger), because the composition of active material, electrolyte concentration and temperature are constantly changing. Ohm's law Ohm's resistance to comply with the polarization resistance increases with current density, but not linear. It Often increases with the current density .
Resistance is an important indicator to decide the battery performance, which directly affects the battery voltage, operating current, the output of energy and power, for the battery, its internal resistance is smaller, it is better.
Main performance parameters of the battery–two
Rated Capacity
In the conditions of the design requirements(such as temperature, discharge rate, termination voltage, etc.), the battery should be able to release the minimum capacity, the unit is in ampere-hours and signed as C. Capacity is greatly influenced by the discharge rate, so often in the lower right corner of the letter C ,the discharge rate is marked with Arabic numerals, such as C20 = 50 shows that when the rates is 20 ,the capacity is 50 ampere-hour . Theoretical capacity of the battery under the battery electrode active material reactive in the amount and calculated according to Faraday's law of electrochemical active substances equivalent spectra. As the battery side effects may occur, and the special needs of design, the actual capacity of the battery is often lower than the theoretical capacity.
Rated Voltage
The typical operating voltage of Battery at room temperature, also known as the nominal voltage. It is used in reference to different types of batteries. Actual battery voltage varies with different conditions. Battery open circuit voltage is equal to the difference of the positive and negative electrode potential electrode balance. Only with the type of electrode active material, whereas the number of independent and active substances. The battery voltage is essentially a DC voltage, but in some special conditions, the electrode reaction caused by the metal crystals or films of certain phase transition into phase voltage will cause small fluctuations, a phenomenon known as noise. Volatility is small but very wide frequency range, so the circuit can be distinguished from self-excited noise.
Main performance parameters of the battery–one
The main features of the battery include battery electromotive force, rated capacity, rated voltage, open circuit voltage, internal resistance, charge and discharge rate, resistance, longevity and self-discharge rate.
Emf
Electromotive force is the electrode potential difference balance between the two electrodes , take lead-acid batteries as an example, E = Ф +0- Ф-0 + RT / F * In (αH2SO4/αH2O).
E-emf
Ф +0- positive standard electrode potential, its value is 1.690
Ф-0-negative standard electrode potential, its value is -0.356
R-universal gas constant, its value is 8.314
T-temperature, it refers to the battery temperature
F-Faraday constant, its value is 96500
αH2SO4-activity of sulfuric acid, and sulfuric acid concentration
αH2O-water activity, and the concentration of sulfuric acid
As can be seen from the above formula, the standard lead-acid battery emf is 1.690-(-0.0.356) = 2.046V, so the battery's nominal voltage is 2V. Lead-acid battery emf relates to the temperature and sulfuric acid concentration.
Something about the Chemical batteries–two
Disposable batteries and rechargeable batteries
Disposable batteries are commonly known as "disposable" batteries, because after their power runs out, you can not recharge for using but only discard. Common Disposable batteries, including one-time battery alkaline batteries, zinc manganese batteries, lithium batteries, zinc batteries, zinc air batteries, zinc and mercury batteries, mercury batteries, hydrogen cells and magnesium-manganese batteries.
Rechargeable battery by making the difference in materials and workmanship, the common batteries are lead-acid batteries, nickel-cadmium batteries, nickel-iron batteries, nickel hydrogen batteries and lithium ion batteries. The advantage is a long cycle life, which can be full charged and discharged for 200 times, and some rechargeable battery power is higher than most of the load off the battery . Ordinary nickel-cadmium, nickel metal hydride battery, the unique memory effect, causing inconvenience to use and often lead to early failure.
Theory of battery charge time
Theory of battery charge time: the battery charger power divides by the output current.
Example: take a battery 800MAH battery for the example, the charger output current is 500MA then charging time is equivalent to 800MAH/500MA = 1.6 hours, when the charger shows charging is completed, the battery still need about half an hour for the complement of electric time.