{"id":218,"date":"2020-04-14T13:12:46","date_gmt":"2020-04-14T10:12:46","guid":{"rendered":"https:\/\/nt-stels.com\/\/?page_id=218"},"modified":"2023-10-03T16:47:51","modified_gmt":"2023-10-03T13:47:51","slug":"%d1%81%d0%bf%d0%be%d1%81%d0%be%d0%b1%d1%8b-%d0%ba%d0%be%d0%bd%d1%82%d1%80%d0%be%d0%bb%d1%8f-%d0%b7%d0%b0%d1%80%d1%8f%d0%b4%d0%b0-%d0%b0%d0%ba%d0%ba%d1%83%d0%bc%d1%83%d0%bb%d1%8f%d1%82%d0%be%d1%80","status":"publish","type":"page","link":"https:\/\/nt-stels.com\/en\/%d1%81%d1%82%d0%b0%d1%82%d1%8c%d0%b8\/%d1%81%d0%bf%d0%be%d1%81%d0%be%d0%b1%d1%8b-%d0%ba%d0%be%d0%bd%d1%82%d1%80%d0%be%d0%bb%d1%8f-%d0%b7%d0%b0%d1%80%d1%8f%d0%b4%d0%b0-%d0%b0%d0%ba%d0%ba%d1%83%d0%bc%d1%83%d0%bb%d1%8f%d1%82%d0%be%d1%80\/","title":{"rendered":"Battery SoC monitoring methods"},"content":{"rendered":"

Battery SoC monitoring methods<\/h2>\n\t
\n\t\t
\n\t\t\t
<\/div>
<\/div><\/div><\/div>\n\t
\n\t\t
\n\t\t\t\n\t\t<\/div>\n\t<\/div>\n

<\/p>\n

The main problem when charging batteries is to find a parameter that allows determining their state of charge (SoC) with sufficient accuracy.
When charging sealed alkaline batteries, several parameters change, such as voltage, temperature, and internal pressure.\u00a0Figure 1 shows the characteristics changes during the charge of a sealed nickel-cadmium battery.\u00a0These parameters provide different sensitivity and have different limitations when used.\u00a0The changes of characteristics when charging nickel-metal hydride batteries are similar, but batteries of this type are more sensitive to overheating during overcharging.<\/p>\n

 <\/p>\n


<\/p>\n

\n
\"\"<\/a>Fig. 1. Characteristics changes of a sealed nickel-cadmium battery during charging<\/figcaption><\/figure>\n<\/div>\n

<\/p>\n

The standard mode of charge is regulated by certain time.\u00a0Voltage monitoring method here is ineffective because voltage at the end of charging at low charge current (Ucon) changes a little. Monitoring voltage, selected in accordance with the manufacturer's recommendations as typical for this type of current source, can lead to undercharging of some batteries and overcharging of others (depending on their individual charging characteristics). \u00a0The passport voltage of the whole battery pack is a statistical parameter. The voltage spread among the cells of one particular batch can be significant. In addition, this value depends on temperature and battery service life.
With a fast charge, using voltage as control parameter proved to be more effective.\u00a0The shape of charging curve shows it.\u00a0In this case, there is no need to focus on a specific value of maximum charging voltage; you just need to set the moment when it reaches its maximum.\u00a0This requires monitoring devices to determine periodically dU\/dt or dU2\/dt2.\u00a0You can observe the maximum charging voltage when overcharging the battery up to 110-120% of rated capacity.
If you stop charging the battery at this moment, the subsequent discharge in standard mode can remove about 95% of the rated capacity.\u00a0To ensure a greater overcharge (up to 140-160%), you must either keep the charge at the same current for the required time, or switch on to a safer charging mode with a lower current.
Nowadays, another criterion is used to control the fast charge: the charge is stopped after the battery voltage decreases by \u0394U after reaching its maximum, thus providing a correct level of battery recharge.
Such monitoring is recommended for fast charge (within 1 hour) of cylindrical alkaline batteries, if the manufacturer allows such charging for a specific type of battery.\u00a0In literature, it is called \u0394U detection.\u00a0The \u0394U of batteries made by different manufacturers can range from 5-10 to 10-20mV. For battery\u2019s SoC monitoring it is more often suggested to use 10mV, when charging the battery at temperature from 0 to 30\u00b0C.\u00a0At the same time, at the beginning of charge (within 5-10 minutes), it is recommended not to measure the voltage of the current source in order to avoid triggering the monitoring system due to a possible voltage surge (and its subsequent slight drop) after long-term storage.
Another parameter of modern sealed alkaline batteries SoC monitoring is temperature.\u00a0Temperature control is most needed for charging nickel-metal hydride batteries.\u00a0The temperature sensor is not installed on each cell, but on one of them in the battery pack.\u00a0Of course, the influence of battery constructive features and the implemented heat exchange conditions make SoC monitoring with absolute temperature T very difficult, because it is not easy to determine this parameter definitely enough.\u00a0GP specialists, for example, studied in detail the charging process of a battery with capacity 2.5Ah with current 0.5C at ambient temperature (Tat) 15-45\u00b0C.\u00a0The battery shut down when the temperature (Tbat) increased to 55 and 60\u00b0C.\u00a0This showed that if the ambient temperature is above 35\u00b0C, then at Tbat = 55\u00b0C a significant battery undercharge takes place. At Tbat=60\u00b0C the undercharge is slightly reduced.\u00a0It is impossible to increase the controlled parameter (Tbat > 60 \u00b0C) higher without increasing the risk of battery failure.
As a rule, all manufacturers recommend the maximum temperature for fast charging not more than 55\u00b0C.\u00a0It should be understood that using temperature SoC monitoring method at elevated ambient temperatures, it is impossible to avoid low battery.\u00a0It is more rational to control another parameter: the speed of temperature change (\u0394T\/\u0394t), which makes possible to diagnose the intensification of side processes during battery overcharging at any ambient temperature.\u00a0The \u0394T\/\u0394t value, at which various manufacturers recommend to disconnect sealed alkaline batteries from power sources, is in the range from 1 to 2\u00b0C\/min with charge current 1C and 0.8\u00b0C\/min if the current is less.
The majority of manufacturers believe that the best results might be achieved by controlling the charge according to two criteria (\u0394U and \u0394T\/\u0394t) simultaneously.\u00a0This method of monitoring is universal both for different types of batteries and for different levels of charge.\u00a0It should be noted that the second parameter provides better conditions for long-term battery life.
Another electrical parameter changes more significantly and is more visible than voltage. This is the response of the current source to the AC test signal.
To control the degree of charge of lead-acid batteries, you can use the open-circuit voltage, which varies from 2.05-2.15V\/ac when charged (depending on the acid concentration) to 1.95-2.03V\/ac after full discharge.\u00a0Figure 2 shows this relationship.<\/p>\n

 <\/p>\n


<\/p>\n

\n
\"\"<\/a>Fig. 2. Dependence of the open circuit voltage of a lead-acid battery on the level of charge<\/figcaption><\/figure>\n<\/div>\n

<\/p>\n

When SoC monitoring of a lead-acid battery the charge is considered complete if the charge current (with the standard charge voltage unchanged) remains unchanged for 3 hours.
When charging lithium-ion batteries, battery SoC is monitored by voltage.\u00a0In the beginning when lithium-ion batteries with graphite system were first introduced, the charge voltage limit 4.1V per cell was required.\u00a0Currently, lithium-ion cells can be charged to voltage of 4.20V.\u00a0The voltage tolerance is only about \u00b10.05V per cell.\u00a0Figure 3 shows the standard charging process for a lithium-ion battery.<\/p>\n

 <\/p>\n


<\/p>\n

\n
\"\"<\/a> Fig. 3. Voltage and current dependence on time when charging a lithium-ion battery<\/figcaption><\/figure>\n<\/div>\n

<\/p>\n

STEP 1 - The maximum permissible charge current flows through the battery until the voltage reaches the threshold value.
STEP 2 - The maximum voltage on the battery is reached, the charge current gradually decreases until it is fully charged.\u00a0The moment when the charge is complete is when the charge current decreases to 3% of the initial value.
STAGE 3 - Periodic compensating charge conducted during storage of the battery, approximately every 500 hours of storage.<\/p>\n

<\/p>\n

 <\/p>\n\n\t\t<\/div>\n\t<\/div>\n<\/div><\/div><\/div><\/div>","protected":false},"excerpt":{"rendered":"\u0421\u043f\u043e\u0441\u043e\u0431\u044b \u043a\u043e\u043d\u0442\u0440\u043e\u043b\u044f \u0437\u0430\u0440\u044f\u0434\u0430 \u0430\u043a\u043a\u0443\u043c\u0443\u043b\u044f\u0442\u043e\u0440\u043e\u0432 \u041e\u0441\u043d\u043e\u0432\u043d\u0430\u044f \u043f\u0440\u043e\u0431\u043b\u0435\u043c\u0430, \u043a\u043e\u0442\u043e\u0440\u0430\u044f \u0432\u043e\u0437\u043d\u0438\u043a\u0430\u0435\u0442 \u043f\u0440\u0438 \u0437\u0430\u0440\u044f\u0434\u0435 \u0430\u043a\u043a\u0443\u043c\u0443\u043b\u044f\u0442\u043e\u0440\u043e\u0432, \u0441\u043e\u0441\u0442\u043e\u0438\u0442 \u0432 \u043f\u043e\u0438\u0441\u043a\u0435 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u0430, \u0438\u0437\u043c\u0435\u0440\u0435\u043d\u0438\u044f \u043a\u043e\u0442\u043e\u0440\u043e\u0433\u043e \u043f\u043e\u0437\u0432\u043e\u043b\u0438\u043b\u0438 \u0431\u044b \u0441 \u0434\u043e\u0441\u0442\u0430\u0442\u043e\u0447\u043d\u043e\u0439 \u0442\u043e\u0447\u043d\u043e\u0441\u0442\u044c\u044e \u043e\u043f\u0440\u0435\u0434\u0435\u043b\u0438\u0442\u044c \u0441\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u0435 \u043f\u043e\u043b\u043d\u043e\u0433\u043e \u0437\u0430\u0440\u044f\u0434\u0430.\u0412 \u0445\u043e\u0434\u0435 \u0437\u0430\u0440\u044f\u0434\u0430 \u0433\u0435\u0440\u043c\u0435\u0442\u0438\u0447\u043d\u044b\u0445 \u0449\u0435\u043b\u043e\u0447\u043d\u044b\u0445 \u0430\u043a\u043a\u0443\u043c\u0443\u043b\u044f\u0442\u043e\u0440\u043e\u0432 \u043c\u0435\u043d\u044f\u0435\u0442\u0441\u044f \u043d\u0435\u0441\u043a\u043e\u043b\u044c\u043a\u043e \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u043e\u0432: \u043d\u0430\u043f\u0440\u044f\u0436\u0435\u043d\u0438\u0435, \u0442\u0435\u043c\u043f\u0435\u0440\u0430\u0442\u0443\u0440\u0430, \u0432\u043d\u0443\u0442\u0440\u0435\u043d\u043d\u0435\u0435 \u0434\u0430\u0432\u043b\u0435\u043d\u0438\u0435. \u0425\u0430\u0440\u0430\u043a\u0442\u0435\u0440 \u0438\u0445 \u0438\u0437\u043c\u0435\u043d\u0435\u043d\u0438\u0439 \u0432 \u043f\u0440\u043e\u0446\u0435\u0441\u0441\u0435 \u0437\u0430\u0440\u044f\u0434\u0430 \u0433\u0435\u0440\u043c\u0435\u0442\u0438\u0447\u043d\u043e\u0433\u043e \u043d\u0438\u043a\u0435\u043b\u044c-\u043a\u0430\u0434\u043c\u0438\u0435\u0432\u043e\u0433\u043e \u0430\u043a\u043a\u0443\u043c\u0443\u043b\u044f\u0442\u043e\u0440\u0430 \u0438\u0437\u043e\u0431\u0440\u0430\u0436\u0435\u043d \u043d\u0430 \u0440\u0438\u0441\u0443\u043d\u043a\u0435 1. \u042d\u0442\u0438 \u043f\u0430\u0440\u0430\u043c\u0435\u0442\u0440\u044b \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0438\u0432\u0430\u044e\u0442 \u0440\u0430\u0437\u043b\u0438\u0447\u043d\u0443\u044e [...]","protected":false},"author":1,"featured_media":1523,"parent":57,"menu_order":32,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/pages\/218"}],"collection":[{"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/comments?post=218"}],"version-history":[{"count":10,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/pages\/218\/revisions"}],"predecessor-version":[{"id":2134,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/pages\/218\/revisions\/2134"}],"up":[{"embeddable":true,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/pages\/57"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/media\/1523"}],"wp:attachment":[{"href":"https:\/\/nt-stels.com\/en\/wp-json\/wp\/v2\/media?parent=218"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}