An expeditious and simple scheme for measuring self‐discharge rate of lithium batteries

Abstract

Summary The inconsistency of the self‐discharge rate of each cell in series has an impact on the capacity of the battery pack, which is one of the best interpretations of the Cannikin Law. The cells with high self‐discharge rate in series determine the pack capacity. In addition, the cells with high self‐discharge rate usually means lower reliability and higher safety risk. Compared to traditional measurement methods, we previously proposed a method to calculate the self‐discharge rate by “pre‐parallel” equalization and then observing the current change of parallel branch. However, this method still has the problems of time‐consuming and difficult in batch sorting. This paper replaces the previous “pre‐parallel” operation with the initial voltage measurement of the cells. Combined with the established equivalent circuit model, the self‐discharge rate of each cell is calculated. The method further shortens the measurement time, which is suitable for sorting the cells in batches. The results show that the method can identify the absolute self‐discharge rate of each cell in a shorter time with relatively high accuracy.

Self‐Feedback Sensing Properties of Self‐Powered Multi‐Parameter Meteorological Sensor with Omnidirectional Array Structure

“…Among them, φ is the local latitude, δ is the declination angle, and ω is the hour angle, they are expressed as follows: $$\[ \begin{array}{*{20}{c}}{\delta = {{23.45}^ \circ }\sin \left\{ {\frac{{\left( {284 + n} \right)}}{{365}} \times 2\pi } \right\}}\end{array} \]$$ $$\[ \begin{array}{*{20}{c}}{\omega = 15^\circ \left( {{t_s} - 12} \right)}\end{array} \]$$where n is the sequence number of the date within the year, t s is the local apparent solar time and it is in the range [0,24). According to the geographical locations of different weather stations, we can get the latitude of Taiyuan, the city where we are located, to be 37.78 ° N. [ 31 ]…”

“…According to the model and correlation used to analyze the solar irradiance, the solar irradiance in different geographical locations can be estimated for experimental analysis reference. [ 31,32 ] The full wavelength solar radiation on the horizontal surface can be calculated by the following equations [ 33 ] : $$\[ \begin{array}{*{20}{c}}{{S_{bn}} = r{S_0}p_2^m}\end{array} \]$$ $$\[ \begin{array}{*{20}{c}}{r = 1 + 0.034\cos \left( {\frac{{2\pi n}}{{365}}} \right)}\end{array} \]$$where S bn is the local instantaneous direct solar radiation intensity, r is the eccentricity correction factor, S 0 is the solar constant (1367 W m −2 ), m is the optical quality of the atmosphere and p 2 is the atmospheric transparency when m = 2. Additionally, m is a function related to the solar altitude angle α s , as shown in Equation 7.…”

“…where n is the sequence number of the date within the year, t s is the local apparent solar time and it is in the range [0, 24). According to the geographical locations of different weather stations, we can get the latitude of Taiyuan, the city where we are located, to be 37.78 ° N. [31] According to the Equations 1-4, the variation in the solar altitude angle and azimuth angle of the four solar terms of March equinox, June solstice, September equinox, and December solstice in one day can be obtained, as shown in Figure 2b,c and Table S1 (Supporting Information). The azimuth angle of the June solstice has the widest variation range, and the altitude angle is the largest, and vice versa on the December solstice.…”

“…According to the model and correlation used to analyze the solar irradiance, the solar irradiance in different geographical locations can be estimated for experimental analysis reference. [31,32] The full wavelength solar radiation on the horizontal surface can be calculated by the following equations [33] :…”

Active Equalization of Lithium-Ion Battery Based on Reconfigurable Topology

“…The former can be caused by variances in the raw materials and manufacturing equipment and procedures, which will lead to variances in physical volume, internal impedance, and self-discharge rate [6]. The self-discharge of lithium-ion batteries means that the charge will gradually decrease even if no load is connected, which will accumulate a lot over a long time and cause significant imbalances in SOCs [7,8]. The latter mainly originate from environmental differences during battery usage and storage.…”