Nickel metal hydride battery design method
Nickel-metal hydride battery designers can design with clear design tasks and adequate preparation. According to the needs of nimH battery users, there are two ways to design the battery: one is to supply rated capacity power for electrical equipment and instruments; The other just gives the external dimensions of the power supply, and develops a new specification battery or abnormal battery with good performance.
Nimh battery design steps:
(1) Determine the number of single batteries and working current density in nimH battery inclusion.
A. According to user requirements, determine the total operating voltage, operating current and other indicators of nimH battery, select the battery series and refer to the voltammetry curve of the series.
(experimental data or obtained experimentally) to determine the operating voltage and operating current density of a single cell.
B. Determine the number of batteries in a battery pack. Number of batteries = Total operating voltage of a battery/Voltage of a battery
(2) Calculate the capacity of nimH battery
A. Calculate the rated capacity according to the required operating current and working time.
Rated capacity = operating current × Working time
Determine design capability.
Design capacity = rated capacity × Design factor
The design coefficient is set to ensure the reliability and service life of the battery, generally 1.1~1.2.
(3) Calculate the active substance content of nimH battery
A. Control the amount of active substance in the electrode.
Control electrode single cell active substance consumption = design capacity × Electrochemical equivalent/utilization ratio
B. Uncontrolled electrode active substance content.
Non-control electrode effective material consumption in a single cell = design capacity × Electrochemical equivalent & Times; Excess coefficient/utilization ratio
The excess coefficient is generally between 1 and 2, such as 1.3 to 1.7 for MI-Ni batteries.
(4) Electrode plate design (determine the total area of the electrode, the number of electrodes, single electrode mass, single electrode thickness).
A. According to the working current and the selected working current density, calculate the total area of the electrode (according to the control electrode).
Total electrode area = operating current/operating current density
B. Select the appropriate electrode size according to the maximum size of the battery and calculate the number of electrodes.
Number of electrodes = total area of electrodes/plate area
C. Calculate the active substance content of a single electrode according to the active substance content of the positive and negative electrodes of a single battery and the number of electrodes.
Amount of single positive (negative) electrode material = amount of positive and negative electrode material in a single battery/number of positive (negative) electrode pieces
D. Determine the thickness of individual electrodes
The network thickness of positive and negative service substance concentration in each dose
Average thickness of positive (negative) electrode = amount of positive (negative) electrode material /(material density × Polar area × (1- porosity))+ collector net thickness
In the formula, collector net thickness = net weight /(mass density × Mesh size)
(5) Selection of battery diaphragm material and determination of thickness and number of layers
According to the battery series and design requirements, choose the appropriate battery diaphragm material and thickness, determine the required diaphragm layer number according to the specific design.
(6) Determine the concentration and dosage of electrolyte
According to the characteristics of the selected battery series, the concentration and amount of electrolyte can be determined according to specific battery design requirements and operating conditions (such as operating current, operating temperature, cycle performance, etc.) or relevant empirical data.
The less electrolyte you use to keep the battery from leaking, the better.
(7) Determine the tightness of the battery and the size of the single battery
The tightness can be calculated by the following formula
Total thickness of elastic rod + total thickness of diaphragm × 100%
The battery inside diameter
For cylindrical cells, cross-sectional areas are also used
Total length of air tight electrode sheet Thickness of electrode sheet + total length of diaphragm Diaphragm thickness is 100%
The cross-sectional area of the battery
The battery's cross-sectional area is equal to T times d2
D is the inner diameter of the battery. The tightness of the battery is determined according to the characteristics of the selected series of batteries and the electrode thickness of the designed battery.