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Changes for page 3.4 Battery parameters

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1 -drafts.bms-main-2-1.configuration.WebHome
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117 117  
118 118  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).
119 119  
120 -[[image:1732207485773-804.png]]
120 +To change the cell balancing parameters, select the menu "Cell → Cell balancing":
121 121  
122 +[[Cell balancing settings>>image:1732207485773-804.png||data-xwiki-image-style-alignment="center" height="264" width="387"]]
122 122  
123 -To change the cell balancing parameters, select the menu "Cell → Cell balancing":
124 +In this section:
124 124  
125 -== SOC correction ==
126 +* Enable – a flag to enable cell balancing;
127 +* Algorithm – a balancing algorithm:
128 +** Balancing stacks individually;
129 +** Balancing the entire battery;
130 +* Constrain (rule):
131 +** Charging;
132 +** Charging or relaxed;
133 +** Always (regardless of battery state);
134 +* Minimum cell voltage to start balancing, V;
135 +* Balancing threshold, V;
136 +* Start cell discharging – a command to start forced balancing of all battery cells (used for service purposes);
137 +* Stop cell discharging – a command to stop forced balancing of all battery cells (used for service purposes).
126 126  
139 +== 3.4.5 Series balancing ==
140 +
141 +The BMS Main 2.x board supports work with two independent (galvanically unrelated) cell series. To monitor the status of two series, two current sensors are used: primary and secondary (AUX). A series of cells must be equivalent: they must have the same number of cells and the same capacity.
142 +
143 +Since the series of cells can operate at different loads, they must be balanced. For this, the BMS Main 2.x provides two relays: “Balancing series 1” and “Balancing series 2” (see section Configuration of output discrete signals and relays), as well as a combined algorithm that considers both the voltage of each series and the charge that these series gave load. “Balancing series 1” and “Balancing series 2” relays are used to connect high-power balancing resistors in parallel with cells series 1 and 2.
144 +
145 +When charging the battery, balancing is performed based on the voltage of the series. A balancing resistor is connected to the cell series if:
146 +
147 +* the series voltage is higher than the starting voltage of the balancing;
148 +* the difference between the voltage of a series of cells and the minimum voltage among the battery series is greater than the balancing threshold.
149 +
150 +When the battery is discharging (work on load), balancing is turned on if one of the series gives the load a charge (Ah), which is more by the amount Qthr of the charge given off by another series.
151 +
152 +To change the series balancing parameters, select the menu "Cell → Series balancing":
153 +
154 +[[Series balancing settings>>image:1732207584941-447.png||data-xwiki-image-style-alignment="center" height="258" width="438"]]
155 +
156 +In this section:
157 +
158 +* Enable – a flag to enable series balancing;
159 +* Number of BMS Logic boards in a series;
160 +* Minimum series voltage to start balancing, V;
161 +* Balancing threshold, V;
162 +* Coulomb threshold – the difference of the charges Qthr, given by a series of cells, above which balancing to be started, Ah;
163 +* Period – period to reset of charge counters for each series (to avoid accumulation of error), second.
164 +
165 +== 3.4.6 Cell analysis ==
166 +
167 +Discharge characteristics of the battery – the dependence Uocv = Uocv (DOD) – is used to determine the tabular dependence Uocv = Uocv (SOC, t °C) (see section Calculating the state of charge (SOC)), which is necessary for calculating the state of charge of the battery.
168 +
169 +The BMS Main 2.x board can automatically determine the battery discharge characteristic.
170 +
171 +Before starting the process of determining the discharge characteristic, it is necessary to prepare a BMS:
172 +
173 +1. Charge the battery.
174 +1. Connect a contactor to the discharging relay which switches the resistive load to the battery.
175 +1. Connect a resistive load to the contactor, which will provide a discharge current of 0.5C (where C is the cell capacitance).
176 +
177 +To configure parameters for determining the discharge characteristic of the battery, select the menu "Cells → Cell analysis":
178 +
179 +[[Cell analysis section>>image:1732207696322-587.png||data-xwiki-image-style-alignment="center" height="213" width="258"]]
180 +
181 +In this section:
182 +
183 +* Enable – a flag to enable cell analysis;
184 +* Discharge step, Ah;
185 +* Delta voltage – a maximum allowable voltage drop for the cell, V;
186 +* Logic index – an address of the BMS Logic board to which the analyzed cell is connected;
187 +* Cell index – a position of the analyzed cell connected to the BMS Logic board;
188 +* Analyse cell with minimum voltage – a flag to analyse of the least charged cell (in this case, the values of Logic index and Cell index are ignored).
189 +
190 +Discharge step should be set equal to
191 +
192 +Discharge step = С/21,
193 +
194 +where C is the cell capacity.
195 +
196 +The discharge characteristic will be constructed for the given cell (its position is determined by the fields Logic index and Cell index).
197 +
198 +The algorithm for determining the discharge characteristic of the battery will be started if the Enable flag is set. From this moment, the control of the discharge relay is performed by this algorithm.
199 +
200 +Algorithm steps:
201 +
202 +1. DOD = 0.
203 +1. Disconnecting the discharge relay.
204 +1. Waiting for the relaxation of the battery.
205 +1. Measuring Uocv = U.
206 +1. Saving the point of the discharge characteristic (Q, U,,OCV,,).
207 +1. Activation of the discharge relay. DOD,,1,, = DOD + Discharge step, U,,1,, = U
208 +1. If DOD = DOD,,1,, or U < (U,,1,, – Delta voltage), then go to step 2.
209 +1. If the "Undervoltage" error is detected, then the end of the algorithm.
210 +
211 +During the operation of the algorithm, a file with the name "CELLANALYSIS.TXT" in the CSV format will be created on the SD card.
212 +
213 +File structure:
214 +
215 +|**Time**|**DOD**|**Logic**|**Cell**|**OCV**|**Resistance**
216 +|**10.11.2017 12:28:34**|0.0|1|1|4.180|0.080000
217 +|**...**|...|…|…|...|...
218 +
219 +Parameter names:
220 +
221 +* Time – date and time;
222 +* DOD – depth of discharge, Ah;
223 +* Logic – the address of the BMS Logic board to which the analyzed cell is connected;
224 +* Cell – position of the analyzed cell for which OCV and Resistance values are provided;
225 +* OCV – cell voltage Uocv, V;
226 +* Resistance – cell resistance, Ohm.
227 +
228 +== 3.4.7 Charge current map ==
229 +
230 +The BMS Main 2.x board calculates maximum allowable charge current values in respect to SOC and battery temperature, contactor temperature and maximum cell voltage.
231 +
232 +Calculated currents values are sending to chargers or intellectual loads over the CAN bus.
233 +
234 +To configure parameters for determining the charge current limit, select the menu "Cells → Charge current map":
235 +
236 +[[Charge current map settings>>image:1732208033738-498.png||data-xwiki-image-style-alignment="center" height="655" width="453"]]
237 +
238 +In this section:
239 +
240 +* Enable – a flag to start calculation of the charge current limit;
241 +* Maximum charging current – a maximum allowable value of the charge current (under normal conditions):
242 +* Limit charging current by the battery SOC and temperature – a flag to enable correction of maximum allowable charging current Kcs depending on SOC and temperature;
243 +* Limit charging current by the contactor temperature – a flag to enable correction of maximum allowable charging current Kcc depending on the contactor temperature;
244 +* Limit charging current by the maximum cell voltage – a flag to enable correction of maximum allowable charging current Kcv depending on maximum cell voltage;
245 +* Limit charging current by the maximum cell temperature – a flag to enable correction of maximum allowable charging current Kct depending on maximum cell temperature.
246 +
247 +Value of the charge current limit at given SOC, temperature, contactors temperature and maximum cell voltage is calculated as follows:
248 +
249 +Charging current limit = Maximum charging current × Kcs × Kcc × Kcv × Kct.
250 +
251 +== 3.4.8 Discharge current map ==
252 +
253 +The BMS Main 2.x board calculates maximum allowable discharge current values in respect to SOC and battery temperature, contactor temperature and maximum cell voltage.
254 +
255 +Calculated currents values are sending to chargers or intellectual loads over the CAN bus.
256 +
257 +To configure parameters for determining the charge current limit, select the menu "Cells → Charge current map":
258 +
259 +[[Discharge current map settings>>image:1732208218667-968.png||data-xwiki-image-style-alignment="center" height="631" width="434"]]
260 +
261 +In this section:
262 +
263 +* Enable – a flag to start calculation of the discharge current limit;
264 +* Maximum discharging current – a maximum allowable value of the discharge current (under normal conditions):
265 +* Current factor – the dependence of the correction factor on SOC and the battery temperature – Kdischarge=Kdischarge (SOC, t°C).
266 +* Limit discharging current by the battery SOC and temperature – a flag to enable correction of maximum allowable discharging current Kds depending on SOC and temperature;
267 +* Limit discharging current by the contactor temperature – a flag to enable correction of maximum allowable discharging current Kdc depending on the contactor temperature;
268 +* Limit discharging current by the maximum cell voltage - a flag to enable correction of maximum allowable discharging current Kdv depending on maximum cell voltage;
269 +* Limit discharging current by the maximum cell temperature - a flag to enable correction of maximum allowable discharging current Kdt depending on maximum cell temperature .
270 +
271 +Value of the discharge current limit at given SOC, temperature, contactors temperature and maximum cell voltage is calculated as follows:
272 +
273 +Discharging current limit = Maximum discharging current × Kds × Kdc × Kdv × Kdt.
274 +
275 +== 3.4.9 SOC correction ==
276 +
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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