Introduce electromotive force and voltage of the battery

Source: 2020 - 04 - 12 then hits: battery electromotive force and voltage ( 1) The electromotive force of battery electromotive force ( E) Equal to constitute a battery of equilibrium potential difference between two electrodes, the E = + - E E - In benign isothermal conditions, such as when the system is changed, the system of gibbs free energy is equal to the reduction of the maximum expansion work. If the expansion work just electrical work, & Delta; GT, P = - NFE type, n for the REDOX reaction of electrode electronic measuring coefficient. When the chemical energy of the battery irreversible into electricity, the potential difference between the poles of E & # 39; Must be smaller than the reversible electromotive force E. Δ GT。 P = (nFE 'type 1 - 21) Gives the maximum limit of chemical energy into electrical energy, and provide the theoretical basis to improve the battery performance. Electromotive force ( 电动势,emf) Is the theoretical value under ideal state of equilibrium, the battery of the positive and negative active material electrochemical activity. The electromotive force of the MH/Ni secondary battery is about. 50 v, actual battery voltage is lower than this value. ( 2) Open circuit voltage and working voltage open circuit voltage is refers to the battery in the open state, Almost no current) When the potential difference between the poles, usually expressed in V: V on = + battery open circuit voltage is equal to the difference between the positive and negative mixed potential of the battery. It highly depends on the positive and negative battery materials, properties of electrolyte and temperature conditions, but has nothing to do with the battery of geometric structure and external dimension. Open circuit voltage of battery is less than the electromotive force in general. Working voltage is refers to the battery during discharge after good load, shows the voltage by the poles, also called load ( Load) Voltage or discharge voltage, the battery discharge initial voltage is called the initial voltage. Due to the ohmic resistance and the existence of the overpotential, the working voltage is lower than the open circuit voltage of the battery, of course also lower than that of electromotive force: V = E - IR = E - 我( RΩ+ Rf) Or V = E - η + - η - IRΩΩ= + - phi phi - IReta + and eta The type of anode polarization and cathodic overpotential, respectively; I is the job of the battery current; R Ω respectively and rf ohmic resistance and polarization resistance; When the current through the + and - Respectively for the positive electrode potential and negative electrode potential and polarization potential. The working voltage of the battery and discharge system, that is to say, all kinds of conditions stipulated by the battery discharge, the discharge model mainly includes the continuous or intermittent, external resistance and the size of the discharge current, discharge time length, determine the final voltage and discharge temperature. ( 3) Rated voltage of rated voltage, rated voltage or rated voltage, is refers to the lowest cell (open circuit voltage Guarantee value) , or it is a standard battery voltage under prescribed conditions, that is to say, the whole process of the average voltage when the battery is 0. 2 c multiplier discharge. Rated voltage can be easy to distinguish the battery system: alkaline manganese battery 1. 5 v, nickel cadmium battery 1. 2 v, lead-acid batteries. 0 v, lithium ion battery 3. 6 v, etc. ( 4) For all secondary battery discharge termination voltage, discharging termination voltage is an important indicator of must be strictly controlled. Discharging termination voltage is also called the discharge by the voltage, is refers to the battery discharge, the voltage drop to the lowest operating voltage is not appropriate to continue to discharge. According to different types of batteries and different discharge conditions, battery capacity and life requirement is different, so the regulation of discharging termination voltage also different. In general, when low or high discharge current, terminal voltage is relatively low; When small current discharge for a long time or intermittent discharge, should be set higher end voltage value. ( 5) The charging pressure charging voltage is refers to the battery when charging, the external power supply to adjust the voltage at the ends of the battery. The basic ways of charging has permanently charging flow and constant voltage charging.