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Changes for page 3.4 Battery parameters

Last modified by Admin on 2025/04/09 12:04
From version 6.2
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on 2024/11/21 16:44
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To version 4.2
edited by Admin
on 2024/11/21 16:25
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61 61  
62 62  The SOC calculation algorithm “Current and voltage (enhanced)” differs from the simplified algorithm by online correction of effective capacitance. When using this algorithm, it is necessary to fine tune the tabular dependence Uocv = Uocv (SOC, t °C).
63 63  
64 -== 3.4.3 Cell resistance estimation ==
64 +== 3.4.3 SOC correction ==
65 65  
66 -Calculation of the resistance of cells is carried out in two ways. The first method is used when the battery passes from a relaxation state to a charge or discharge state, wherein the cell resistance value
67 -
68 -R = (U-Uocv) / Istable,
69 -
70 -where U is the cell voltage measured in the charge or discharge state, V; Uocv is the cell voltage measured in the state of relaxation (before switching to the state of charge or discharge); Istable – stabilized current through the cell in the state of charge or discharge.
71 -
72 -The second method is used for a stepwise change in the current through the cell, while the value of the cell resistance:
73 -
74 -R = (U,,2,,-U,,1,,) / (I,,stable2,,-I,,stable1,,) provided that | I,,stable2,,-I,,stable1,, | > 0.2 × Q,,max,,
75 -
76 -(Q,,max,, is the maximum cell capacity),
77 -
78 -where U,,2,, is the voltage on the cell at the moment when the stabilized current I,,stable2,, is flowing through it; U,,1,, – the voltage on the cell at the moment when the stabilized current I,,stable1,, flowing through it.
79 -
80 -The stabilized current I,,stable,, = I, if during the stabilization time the instantaneous current I is in the range from 0.95 × I to 1.05 × I.
81 -
82 -To change parameters of the algorithm for calculating the cell resistance, select the menu "Cells → Cell resistance estimation":
83 -
84 -[[Cell resistance estimation settings>>image:1732207338609-903.png||data-xwiki-image-style-alignment="center" height="187" width="337"]]
85 -
86 -In this section:
87 -
88 -* Current stabilization time, second;
89 -* Maximum estimation period – maximum time between resistance measurements. If more time has elapsed since the last determination of the stabilized current Istable than is determined in this field, the resistance calculation is not performed, second;
90 -* Maximum resistance factor – the coefficient of calculation of the maximum acceptable resistance of the cell;
91 -* Minimum SOC – minimum cell SOC value for resistance calculation;
92 -* Maximum SOC – maximum cell SOC value for resistance calculation.
93 -
94 -The calculated resistance is accepted by the system as valid (and therefore updated) if its value is in the range from Resistance/2 to “Maximum resistance factor” × Resistance, where "Resistance" is the nominal resistance of the cell (see section Cell defaults). If the calculated resistance value is greater than the value (Maximum resistance factor × Resistance), the updated resistance value will be equal to the value (Maximum resistance factor × Resistance).
95 -
96 -== 3.4.4 Cell balancing ==
97 -
98 -The BMS Main 2.x supports two cell balancing algorithms:
99 -
100 -* balancing stacks individually;
101 -* balancing the entire battery (used by default).
102 -
103 -Balancing stacks individually balances the voltage within a group of cells that are connected to the same BMS Logic board. **It is not recommended to use this algorithm in typical battery designs**.
104 -
105 -Balancing the entire battery makes the voltage of all cells be equal to the minimum cell voltage.
106 -
107 -The following balancing rules are supported:
108 -
109 -* only when the battery is charging (current I > 0);
110 -* when the battery is charging (current I > 0) or when the battery is in a state of relaxation;
111 -* always (regardless of battery state).
112 -
113 -A balancing resistor is connected to the cell if:
114 -
115 -* the voltage on the cell is higher than the starting voltage of the balancing;
116 -* the difference between the cell voltage and the minimum voltage among the cells of the battery is greater than the balancing threshold.
117 -
118 -If the BMS Logic board overheats, then the balancing of the cells connected to this board will not be performed (see Logic high temperature protection).
119 -
120 -[[image:1732207485773-804.png]]
121 -
122 -
123 -To change the cell balancing parameters, select the menu "Cell → Cell balancing":
124 -
125 -== SOC correction ==
126 -
127 127  The BMS Main 2.x board can recalculate the battery SOC after long-term storage or after long-term working in the case when the battery was not charged fully or discharged totally. Recalculation is done based on the tabular dependency Uocv = Uocv (SOC, t) (see section Calculating the state of charge (SOC)).
128 128  
129 129  To configure parameters for periodically correcting the battery state of charge, select the menu "Cells → SOC correction":
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130 130  
131 131  [[SOC correction settings>>image:1732206262509-786.png||data-xwiki-image-style-alignment="center" height="291" width="298"]]
132 132  
133 - In this section:
134 -
135 -* Enable – a flag to enable SOC correction;
136 -* Shutdown period – a time the battery is off, day. If the BMS detects on its startup that it was off during the “Shutdown period” time, the BMS recalculates the battery state of charge base on the tabular dependency Uocv = Uocv (SOC, t);
137 -* Correction period – a period of correcting the battery SOC, day. If the BMS detects that the last correction was more than the “Correction period” ago, the BMS recalculates the battery state of charge base on the tabular dependency Uocv = Uocv (SOC, t) and tunes it gradually during the “SOC change time”;
138 -* SOC change time – a duration of the linear changing the battery SOC to the value calculated by the correction algorithm, minute.
139 -
140 140  
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