WO2022218784A1

WO2022218784A1 - Heating of battery in entrance system

Info

Publication number: WO2022218784A1
Application number: PCT/EP2022/059170
Authority: WO
Inventors: Thomas LÖVSKOG; Jonas STORM
Original assignee: Assa Abloy Entrance Systems Ab
Priority date: 2021-04-13
Filing date: 2022-04-07
Publication date: 2022-10-20

Abstract

A method (200) of heating a battery is disclosed. The battery is arranged in an entrance system for providing power to one or more electric motors of the entrance system. The method (200) comprises monitoring (210) of a current temperature of the battery and a current state of charge of the battery. If the current temperature of the battery is below a first temperature threshold and the current state of charge of the battery is below a first charge threshold, the battery is discharged (220) by means of a load impedance until the current temperature of the battery is above a second temperature threshold. An entrance system is also disclosed.

Description

Heating of battery in entrance system

TECHNICAL FIELD

The present invention relates to a control method of an entrance system and more precisely to a control method of heating a battery comprised in an entrance system.

BACKGROUND

Entrance systems having automatic door operators are frequently used for providing automatic opening and closing of one or more movable door members. These entrance systems may comprise sectional door operator systems for providing automatic opening and closing of doors to facilitate entrance and exit to buildings, cargo bays, rooms and other areas. The door operator systems typically comprise a number of drive units responsible for driving the sectional door between closed and open positions. The sectional door operator systems are typically used in both private and public areas during long time periods and under various conditions in terms of time of day, time of week, time of year, passage frequencies, etc. Therefore, the systems need to remain long-term operational without malfunctions even during heavy traffic by persons or objects passing through the doors. At the same time, safety is crucial in order to ensure that the entrance system is operational also in case of emergencies like fire etc.

Many entrance systems utilize electric motors in order to transition the doors from a closed state to an open state and/or vice versa. Many of the doors, e.g. sectional doors for cargo bays, are very heavy and the electric motors driving the doors have to be heavy duty equipment in order to exert the required torque to open and/or close the door. The electric motors require significant amounts of current when putting the door into motion, currents of 30 to 40 A are not unusual. In order not to have to source this current directly from a mains supply, the entrance system may be provided with a rechargeable battery that is used to drive the high currents for the electric motors. The battery may be used as the sole source of power in case of e.g. a power outage and in many cases it is crucial that the entrance system is operational also in cases of power outage. The temperature of the rechargeable battery is very important since, for instance a lithium based battery can be severely damaged if charged at too low temperature. In addition to this, as the temperature drops, the internal resistance of the battery increases and the ability of the battery to provide high currents decreases. Also, the usable energy stored in the battery decreases with temperature. In other words, there is a risk that a door will not open at all, or will only open to a certain degree if the temperature of the battery driving the electric motor of the entrance system is too low.

Prior art entrance systems are in some cases provided with heating elements arranged to ensure that the batteries are maintained at a desired temperature. These heating elements are typically powered by the same power source that is used to charge the batteries. Apart from not working in cases of a power shortage, these heating elements are very costly and could significantly add to the cost of the bill of material of an entrance system.

From the above it is understood that there is room for improvements.

SUMMARY

An object of the present invention is to provide a new type of method of heating batteries of entrance systems which is improved over prior art and which eliminates or at least mitigates the drawbacks discussed above. More specifically, an object of the invention is to provide a method of heating batteries and an entrance system with heated batteries wherein the heating functionality has little or no impact on the cost of the bill of material of an entrance system. These objects are achieved by the technique set forth in the appended independent claims with preferred embodiments defined in the dependent claims related thereto.

In a first aspect of the invention, a method of heating a battery is presented.

The battery is arranged in an entrance system for providing power to one or more electric motors of the entrance system. The method comprises monitoring a current temperature of the battery and a current state of charge of the battery. If the current temperature of the battery is below a first temperature threshold and the current state of charge of the battery is below a first charge threshold, the battery is discharged by means of a load impedance until the current temperature of the battery is above a second temperature threshold.

In one embodiment of the method, the load impedance is further configurable to be arranged to dissipate power generated by said one or more electric motors. This means that the load impedance can have two functions which reduces the need for additional components of the entrance system when performing the method of the invention. In other words, the cost of the entrance system can be reduced.

In one embodiment of the method, the step of discharging comprises controlling one or more switches to electrically connect the load impedance to the battery and electrically disconnect said one or more electric motors from the battery. Having switches such as relays, transistors or other switching means is beneficial since it allows for automatic control of the state of the switches, further to this, by selectively isolating the electrical motor from the battery reduces the risk that the motor is unintentionally operated during discharging of the battery, thereby reducing the risk of violating any standard requirement, e.g. EN, FCC requirements etc.

In one embodiment of the method, the load impedance is one or more of said one or more electric motors of the entrance system and the step of discharging further comprises controlling a discharge current flowing through said one or more electric motors such that said one or more electric motors are not operated. Having the electric motors also configurable to act as the load impedance reduces the need for additional components and the cost of the entrance system can be reduced. Controlling the current such that the electrical motor is not activated reduces the risk that the motor is unintentionally operated during discharging of the battery, thereby reducing the risk of violating any standard requirement, e.g. EN, FCC requirements etc.

In one embodiment of the method, the step of discharging further comprises controlling the discharge current flowing through the load impedance, preferably by means of PWM control of one or more switches arranged to connect and disconnect the load impedance from the battery. Controlling the discharge current is beneficial as it enables more advanced control of the heating of the battery. The rate of the temperature rise of the battery can be decreased as the current temperature of the battery closes in on the second temperature threshold. The control of the current temperature of the battery be implemented with an integral part and/or a derivative part as a PI-, PD or PID controller.

In one embodiment of the method, the step of monitoring further comprises monitoring a current temperature time derivative of the current temperature of the battery and if the current temperature time derivative is below a temperature derivative threshold, performing the step of discharging the battery. This enables a predictive algorithm for controlling the current temperature of the battery.

In one embodiment of the method, the step of monitoring further comprises monitoring an exterior temperature. The exterior temperature is external to the battery, and if the exterior temperature is below an exterior temperature threshold, performing the step of discharging the battery. The exterior temperature may be an outside temperature and by monitoring also exterior temperature, sudden drops can be detected and a smarter, more energy efficient heating of the battery can be implemented.

In one embodiment of the method, it further comprises, if the current temperature is above the second temperature threshold, and the current state of charge is below a second charge threshold, charging the battery until the current state of charge of the battery is above a third charge threshold. Recharging the battery only when its temperature is above a threshold reduces the risk of damaging the battery during charging and only charging the battery when its current state of charge is below a threshold reduces the number of charging cycles of the battery. Combined, the life of the battery is extended with all savings on cost and the environment as this entails.

In one embodiment of the method, the third charge threshold is lower than a maximum state of charge of the battery, preferably lower than 95 % of the maximum state of charge of the battery. Having the threshold where the charging is stopped at a level below the maximum state of charge of the battery is beneficial as this will increase the number of charging cycles the battery can withstand without deteriorating, thereby the life of the battery is extended with all savings on cost and the environment as this entails.

In a second aspect of the invention, an entrance system is presented. The entrance system comprises one or more electric motors, a load impedance, a controller module and a battery connectable to provide power to said one or more electric motors. The control module is configured to monitor a current temperature of the battery and a current state of charge of the battery. If the current temperature of the battery is below a first temperature threshold and the current state of charge of the battery is below a first charge threshold, then the control module is configured to discharge the battery by means of the load impedance until the current temperature of the battery is above a second temperature threshold.

In one embodiment of the entrance system, it further comprises one or more switches to electrically connect the load impedance to the battery and electrically disconnect said one or more electric motors from the battery. Having switches such as relays, transistors or other switching means is beneficial since it allows for automatic control of the state of the switches, further to this, by selectively isolating the electrical motor from the battery reduces the risk that the motor is unintentionally operated during discharging of the battery, thereby reducing the risk of violating any standard requirement, e.g. EN, FCC requirements etc.

In one embodiment of the entrance system, the load impedance is further connectable to dissipate power generated by said one or more electric motors. This means that the load impedance can have two functions which reduces the need for additional components of the entrance system. In other words, the cost of the entrance system can be reduced.

In one embodiment of the entrance system, the load impedance is one or more of said one or more electric motors, and the control module is further configured to control, when discharging the battery by means said one or more electric motors, a discharge current flowing through said one or more electric motors such that said one or more electric motors are not operated. Having the electric motors also configurable to act as the load impedance reduces the need for additional components and the cost of the entrance system can be reduced. Controlling the current such that the electrical motor is not activated, reduces the risk that the motor is unintentionally operated during discharging of the battery, thereby reducing the risk of violating any standard requirement, e.g. EN, FCC requirements etc. In one embodiment of the entrance system, it further comprises a charging module. The control module is further configured to, if the current temperature is above the second temperature threshold, and the current state of charge is below a second charge threshold, charge the battery until the current state of charge of the battery is above a third charge threshold. The charging module is very beneficial since it enables the recharging of the battery, and in the entrance system according to the invention, recharging the battery only when its temperature is above a threshold reduces the risk of damaging the battery during charging and only charging the battery when its current state of charge is below a threshold reduces the number of charging cycles of the battery. Combined, the life of the battery is extended with all savings on cost and the environment as this entails.

In one embodiment of the entrance system, the third charge threshold is lower than a maximum state of charge of the battery, preferably lower than 95 % of the maximum state of charge of the battery. Having the threshold where the charging is stopped at a level below the maximum state of charge of the battery is beneficial as this will increase the number of charging cycles the battery can withstand without deteriorating, thereby the life of the battery is extended with all savings on cost and the environment as this entails.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will be described in the following; references being made to the appended diagrammatical drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice.

Figures la-d are schematic sectional views of entrance systems workable with embodiments of the invention.

Figure 2 is a block diagram of an automatic door operator according to embodiments of the invention.

Figure 3 is a time series plot of temperature and state of charge of an entrance system according to embodiments of the invention. Figure 4 is a time series plot of temperature and state of charge of an entrance system according to embodiments of the invention.

Figures 5a-c are simplified electric schematics of part of an entrance system according to embodiments of the invention.

Figure 6 is a schematic view of a method of heating a battery according to embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, certain embodiments will be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention, such as it is defined in the appended claims, to those skilled in the art.

The terms "substantially," "approximately," and "about" are defined as largely, but not necessarily wholly what is specified, as understood by a person of ordinary skill in the art. The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including") and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. As a result, a method that "comprises," "has," "includes" or "contains" one or more steps possesses those one or more steps, but is not limited to possessing only those one or more steps.

With reference to Figures la to Id, different types of entrance systems 100 in which the present invention can be implemented will be described. Starting with Figure la, a first embodiment of an entrance system 10 in the form of a sliding door system 10 is shown in a schematic top view. The sliding door system 10 comprises first and second sliding doors or wings D1 and D2, being supported for sliding movements Ml and M2 in parallel with first and second wall portions 20 and 25. The first and second wall portions 20 and 25 are spaced apart; in between them there is formed an opening which the sliding doors D1 and D2 either blocks (when the sliding doors are in closed positions), or makes accessible for passage (when the sliding doors are in open positions). An automatic door operator 100, not seen in Figure la but will be explained below, causes the movements Ml and M2 of the sliding doors D1 and D2.

In Figure lb, another embodiment of an entrance system 10 in the form of a revolving door system 10 is shown in a schematic top view. The revolving door system 10 comprises a plurality of revolving doors or wings D1-D4 being located in a cross configuration in an essentially cylindrical space between first and second curved wall portions 27 and 28 which, in turn, are spaced apart and located between first and second wall portions 20 and 25. The revolving doors D1-D4 are supported for rotational movement Ml in the cylindrical space between the first and second curved wall portions 27 and 28. During the rotation of the revolving doors D1-D4, they will altematingly prevent and allow passage through the cylindrical space. An automatic door operator 100, not seen in Figure lb but will be explained below, causes the rotational movement Ml of the revolving doors D1-D4.

A further embodiment of an entrance system 10 in the form of a swing door system 10 is shown in a schematic top view in Figure lc. The swing door system 10 comprises a single swing door D1 being located between a lateral edge of a first wall 20 and an inner surface of a second wall 25 which in this embodiment is perpendicular to the first wall 20. The swing door D1 is supported for pivotal movement Ml about pivot points on or near the inner surface of the second wall 25. The first and second walls 20 and 25 are spaced apart; in between them an opening is formed which the swing door D1 either blocks (when the swing door is in closed position), or makes accessible for passage (when the swing door is in open position). An automatic door operator 100, not seen in Figure lc but will be explained below, causes the movement Ml of the swing door Dl.

Turning to Figure Id, an embodiment of an entrance system 10 in the form of a sectional door system 10 is shown in a schematic front view. The sectional door system 10 comprises a sectional door Dl which in turn comprises a plurality of horizontal and interconnected sections Dla-e forming the sectional door Dl. The sectional door Dl is located between a first wall 20 and a second wall 25. The first and second walls 20 and 25 are spaced apart; in between them an opening is formed in which the sectional door D1 is sandwiched between tracks 23 attached to the first and second walls 20 and 25. The sectional door D1 is supported for vertical movement Ml along the tracks 23. The tracks 23 may be arranged to change directions to a substantially horizontal direction at an upper section of the sectional door Dl. The sectional door D1 is arranged to either block the opening, when the sectional door Dl is in a lower closed position, or make the opening accessible for passage, when the sectional door Dl is in an upper open position. An automatic door operator 100, causes the movement Ml of the sectional door Dl.

With continued reference to Figure Id, the automatic door operator 100 typically comprises one or more electric motors 110 operatively connected to move the door or swing according to its intended movement Ml, M2. In the embodiment of Figure Id, the electrical door operator 100 is connected to the rails 23 by means of a transmission 105 and the automatic door operator 100 is arranged on one of the sections Die of the sectional door Dl. As the sectional door Dl is opened, i.e. raised, the section Die carrying the automatic door operator 100 is raised, and the automatic door operator 100 is moved along the rails 23. Since the electric motors 110 consume large currents when operated, having a flexible cabling being able to source high currents would be very expensive and cumbersome. Therefore, the automatic door operator is typically provided with a battery 120 arranged to source the high currents directly to the one or more electric motors 110, reducing the need of heavy duty cables between a power source, e.g. mains power, and the electric motor 110. Albeit only the embodiment of Figure Id, sectional door system 10, is illustrated with the automatic door operator 100, other entrance systems 10 are also usable with an automatic door operator 100 comprising a battery 120 and the present invention is relevant for any entrance system 10 comprising a battery 120 for driving one or more electric motors 110 of the entrance system 10. The battery 120 may be any suitable battery but is preferably a battery using lithium based chemistry such as a Lithium-Ion, Li-Ion, or Lithium Polymer, LiPo, type batteries 120.

In Figure 2, a schematic view of the electrical door operator 100 according to one embodiment is shown. The electrical door operator 100 comprises a control module 130 operatively connected to at least one electric motor 110. The electric motor 110 may be comprised in the electrical door operator 100, or operatively connected to the electrical door operator 100. The control module 130 is operatively connected to one or more batteries 120 and preferably to an external power source 150. The control module 130 is configured to drive the electric motor 110. The electrical door operator 100 is typically provided with a suitable wired or wireless external interface, not shown, for sending and/or receiving operational data and/or control data associated with e.g. operation of the entrance system 10.

As explained above, the temperature of the battery 120 is very important, and in order to measure a current temperature T_c of the battery 120, the battery 120 may be provided with one or more temperature sensors 125. The battery 120 is typically formed as a battery pack 120 comprising a plurality of battery cells connected in series and/or parallel in order to provide the required voltage and capacity for the electrical door operator 100. The temperature sensor 125 is typically embedded in the battery pack 120 and may be any suitable temperature sensor 125 such as a simple resistive element having a positive temperature curve, PTC, or a resistive element having a negative temperature curve, NTC. The temperature sensors 125 of the battery 120 are arranged to measure a current temperature T_c equal to, or related to a cell temperature of the battery 120.

The current temperature T_c of the battery is provided to the control module 130 for monitoring. The control module 130 is further configured to monitor a current state of charge SOCc of the battery 120. The state of charge is the ratio of a currently available capacity Q_c and the maximum possible charge that can be stored in a battery 120, i.e., the nominal capacity Qn of the battery 120. The current state of charge SOCc of the battery and/or the currently available capacity Qc may be determined in any suitable means known from the art such as, but not limited to, voltage based methods, current integration method, coulomb counting or combinations thereof.

The control module 130 may further be provided with a charging module 135 for charging the battery 120. There may be entrance systems 10 that are configured to be portable or for other reasons are provided without a charging module 130. The present invention is applicable also for these types of entrance systems 10.

An internal resistance Ri is inherent to all batteries 120, and albeit lithium based batteries 120 have a comparably low internal resistance Ri, typically in the range of 50 mO to 500 ihW, it is still high enough to generate heat when dissipating power in the internal resistance Ri. In addition, as mentioned earlier, the internal resistance Riis high enough to limit a maximum current possible to be sourced from the battery 120 as the voltage drop across the internal resistance Ri is based on the sourced current according to Ohms law. As mentioned, the internal resistance Ri increases as the current temperature T_c decreases. One key aspect of the control module 130 is that it, based on the current state of charge SOCc and the current temperature T_c, selectively heats the battery 120 by utilizing the internal resistance Ri of the battery 120. This is accomplished by loading, i.e. discharging, the battery by means of a load impedance ZL. The load impedance ZLmay, as is explained in other sections of this disclosure, be comprised in the control module 130 and/or in the electric motor 110. Using the internal resistance Ri to heat the battery 120 is very beneficial as the battery cells will be heated from the inside, thus providing a much more efficient heating of the battery 120. The battery 120 can be heated to a desired temperature without having a surface temperature of the battery 120 increase more than necessary, as would have been the case if an external heating element was used. Consequently, using the internal resistance Ri to heat the battery 120 is also more energy efficient and thereby environmentally friendly compared to using external heating elements.

A discharge current Id, the current that will flow though the load impedance ZL during discharge, will depend an impedance of the load impedance ZL. The increase of the current temperature Tc of the battery 120 will depend on the discharge current Id, the internal resistance Ri of the battery 120 and a specific heat capacity C_P of the battery 120. The specific heat capacity of the battery 120 is inherent to the design and chemistry of the battery 120, and measure the amount of energy required to heat 1 kg of a compound 1 Kelvin, a typical heat capacity of a Lithium based battery is in the region of 1,0 to 2,5 J/ y_nor u. The specific heat capacity of a battery having a mass m and can be calculated according to Equation la below, where EDT is the energy required to raise the temperature of the battery DT degrees. The energy E dissipated in the battery 120 when discharging is calculated according to Equation lb below, where t is the discharge time. _r _ E_&T Lp — Eqn. la

AT-m E = /J R_I t Eqn. lb

The equations above can be combined and the end result can be used to optimize the heating based on discharge time or a discharge current Id in order to arrive at a desired current temperature Tc of the battery 120 within a desired time.

With reference to Figure 3, showing a time series plot of the current temperature T_c and the current state of charge SOC_c,the conceptual idea of the present invention will be explained. In the plot of Figure 3, the current state of charge SOCc and the current temperature T_c drops over time t. The drop in current state of charge SOCc may be e.g. due to the drop in current temperature T_c and/or self-discharge of the battery 120. As the current temperature T_c of the battery 120 drops below a predefined or configurable first temperature threshold TTI, the battery 120 is discharged via the load impedance ZL. AS the battery 120 is discharged, the current temperature T_c of the battery 120 increases, and the discharging preferably continues until the current temperature T_c of the battery 120 is a predefined or configurable second temperature threshold TT2. In Figure 3, this can be seen as the solid line showing the current temperature T_c, tilting upwards, i.e. increase, after having fallen below the first temperature threshold TTI and then, after crossing the second temperature threshold TT2, start to tilt downwards, i.e. decrease, again as the discharging has seized. The first temperature threshold TTI is at a lower temperature than the second temperature threshold TT2.

In Figure 3, a dotted line illustrates the current state of charge SOCc, and as the current temperature T_c start to increase, the drop in current state of charge SOCc seize and the current state of charge SOCc effectively increases until the discharging is stopped, after which the current state of charge SOCc drops once more.

Note that the plot in Figure 3 is for illustrative purposes only and the slope of the current state of charge SOCc will depend greatly on the amount of energy consumed when discharging the battery 120 in order to increase the temperature of the battery 120, and the temperature dependency of the currently available capacity Q_c of the battery 120. Low temperatures of the battery 120 effect the currently available capacity Q_c of the battery 120 and the possibility to charge the battery 120 without damaging it, it is beneficial to only heat the battery 120 by discharging of the battery 120 by means of the load impedance ZL only when the current state of charge SOCc is below a first charge threshold Tsoci. This is done in order not to cycle the battery 120 more than necessary, as batteries have a limited amount of charge/discharge cycles. The actions and monitoring described above with reference to Figure 3, are preferably performed by the control module 130 of the electrical door operator 100.

The second temperature threshold TT2 is greater than or equal to the first temperature threshold TTI. The second temperature threshold TT2 is preferably set at a level at which the battery 120 have a current temperature T_c at which the battery 120 can be charged without being damaged. The second temperature threshold TT2 is preferably in the range of 5 to 40 °C, more preferably in the range of 5 to 20 °C and most preferably in the range of 10 to 15 °C.

In Figure 4, charging capabilities are available, e.g. embodiments wherein the control module 130 comprises the charging module 135. As the current temperature T_c of the battery 120 drops below the first temperature threshold TTI and the current state of charge SOCc drops below the first charge threshold Tsoci, the discharging by means of the load impedance ZL is started. The current temperature Tc of the battery 120 increases, and as the current temperature Tc of the battery 120 is above the second temperature threshold TT2, discharging by means of the load impedance ZL is stopped and charging of the battery 120 is started. The current state of charge SOCc of the battery 120 is below a second charge threshold Tsoc2 and the battery 120 is charged, effectively increasing the current state of charge SOCc of the battery 120. The current state of charge SOCc is monitored such that the charging can be stopped when the current state of charge SOCc reaches a third charge threshold Tsoc3. As the battery 120 is charged, the current temperature T_c of the battery 120 typically increase. The actions and monitoring described above with reference to Figure 4, are preferably performed by the control module 130 of the electrical door operator 100.

Although not illustrated in the Figures 3 or 4, other temperature and/or charge thresholds may be implemented. If, due to unforeseen actions or extreme utilization of the entrance system 10, the state of charge SOCc of the battery 120 should be at a level where it is too low to increase the current temperature T_c of the battery 120 and/or operate the entrance system 10, an error message could be generated by the control module 130. Alternatively or additionally, scheduling features may be added such that the controlled discharging of the battery 120 by means of the load impedance ZL is scheduled at times where utilization of the entrance system 10 is low.

Batteries in general, and Lithium based batteries in particular have a limited number of charge/discharge cycles before their nominal capacity Qn start to drop and the battery deteriorates. At least in the case of Lithium based batteries, the number of charge/discharge cycles of a battery 120 is reduced if the battery 120 is fully charged or fully discharged. In order to increase the life time of the battery, the third charging threshold Tsoc3, the threshold at which charging is stopped, is preferably lower than a maximum state of charge SOCMAX, i.e. when the currently available capacity Q_c of the battery 120 is substantially equal to the nominal capacity Qn of the battery 120. Even more preferably, lower than 95 % of the maximum state of charge SOCMAX of the battery 120, and most preferably, lower than 90 % of the maximum state of charge SOCMAX. Similarly, the second charging threshold Tsoc2, the threshold at which charging is started of the current temperature of the battery Tc is above the second temperature threshold TT2, is typically above a minimum state of charge SOCMIN, i.e. when the currently available capacity Q_c of the battery 120 is substantially zero. Even more preferably, more than 5 % of the minimum state of charge SOCMIN of the battery 120, and most preferably, more than 10 % of the minimum state of charge SOCMIN. It should be understood that the first charging threshold Tsoci is larger than, or equal to the second charging threshold Tsoc2, and the third charging threshold Tsoc3 is equal to or larger than the first charging threshold Tsoci but the third charging threshold Tsoc3 is always greater than the second charging threshold Tsoc2.

The drop in the current temperature Tc of the battery 120 as described above and illustrated in Figures 3 and 4, is due to the ambient temperature of the electrical door operator 100. Often, the electrical door operator 100 is used to control doors that separate a heated indoor environment from an outside and the electrical door operator 100 is mounted at a location with comparably good heat conduction to the outside. This is the case with for instance warehouse sectional door systems 10, where the doors D1 are located at docking bays. In order to increase the predictability of the current temperature Tc of the battery 120, some embodiments of the invention monitor also an exterior temperature that is external to the battery 120. If the exterior temperature is below an exterior temperature threshold, the control module 130 is configured to discharge the battery 120 to increase the current temperature Tc of the battery 120. The exterior temperature may be provided by any suitable temperature sensing means operative connector to, e.g. the control module 130 of the electrical door operator 100. The connection to the control module 130 may be any wired or wireless connection and it may be that the exterior temperature is provided to the control module 130 based on weather data available through a cloud service.

As mentioned, the monitoring of the current temperature Tc of the battery 120 and, where applicable, the exterior temperature, is preferably done by the control module 130. The control module 130 may further be configured to determine trends of the current temperature Tc of the battery 120 and/or the exterior temperature. The control module 130 can be configured to monitor a current time derivative of the current temperature Tc, a current temperature time derivative. Discharging of the battery 120 in order to increase the current temperature Tc of the battery 120 may be performed if the current temperature time derivative is below a predetermined or configurable temperature derivative threshold. Additionally, or alternatively, the control module 130 may be configured to monitor a current time derivative of the exterior temperature, an exterior temperature time derivative. Discharging of the battery 120 in order to increase the current temperature Tc of the battery 120 may be performed if the exterior temperature time derivative is below a predetermined or configurable exterior temperature derivative threshold.

All electric motors 110 are inductive and if they are forced to rotate by external forces, they will induce an electric potential across windings of the electric motor 110.

In an entrance system 10, this will happen when a door is returned to an idle position, such as when the sectional door system 10 of Figure Id is returned to its lower closed position. If nothing is done to handle the induced potential, it can build up to several thousands of volts causing voltage transients that can severely damage the electrical motor 110 and/or the automatic door operator 100. In order to avoid this, the energy generated when the entrance system 10 is returned to its idle position is returned to the battery 120 and/or dissipated in a load, preferably the load impedance ZL. With reference to Figures 5a-c, simplified electric schematics of part of the entrance system 10 according to embodiments of the invention, optional configurations of the load impedance ZL will be explained. In all Figures 5a-c, the load impedance ZL is arranged to be connected in parallel with the battery 120 or the electric motor 110. In Figure 5a, the connection of the load impedance ZL is determined by a first switch Si arranged to either disconnect the load impedance from both the battery 120 and the electrical motor 110, connect the load impedance ZL to only the electrical motor 110 or connect the load impedance ZL only to the battery 120. This type of switch Si is commonly referred to a single pole three throw, SP3T. In embodiments where SP3T switches are undesirable, the embodiment of Figure 5b offers an alternative by utilizing two switches Si, S2. The first switch SI is connected to control the general activation of the load impedance ZL, and a second switch S2, a single pole dual throw switch, SPDT, is used to connect either the battery 120 or the electric motor 110 to the load impedance ZL. Alternatively, as illustrated in Figure 5c, several switches S1-S3 can be utilized to control the connection of the load impedance ZL. In the embodiment of Figure 5c, simple on-off switches such as simple relays or single transistors can be used. The first switch Si is connected to control the general activation of the load impedance ZL, the second switch S2 connects the electric motor 110 to the first switch Si and a third switch S3 connects the battery 120 to the first switch Si.

The embodiments exemplified with reference to Figures 5a-c are exemplary only and the skilled person understands, after reading this disclosure, that many further configurations are possible, e.g. incorporating motor control switches etc. The control of switches S1-₃ is preferably provided by the control module 130, and none, some or all of the switches S1-₃ may be comprised in the control module 130 and the remaining switches S1-₃ may be external to the control module 130. The load impedance ZL may be any suitable load impedance ZL, preferably the load impedance ZL is a resistive load impedance ZL, more preferably in the form of a power resistor ZL.

The load impedance ZL may optionally be provided by the electrical motor 110 itself. By controlling the electrical motor 110 such that it is not operated, the electrical motor 110 will act as a load impedance ZL for the battery 120. The use of the electrical motor 110 as load impedance ZL may be accomplished in different ways depending on the type of electric motor 110. If the electric motor 110 is a permanent magnet synchronous motor 110, which are commonly used in entrance systems 10, a current can be applied to the different windings of the permanent magnet synchronous motor 110 such that a rotor of the permanent magnet synchronous motor 110 is not rotated, i.e. the applied currents may be configured to drive the rotor in opposite directions.

The different embodiments of the load impedance ZL, i.e. the external load impedance ZL or the use of the electric motor 110 as load impedance ZL are possible to combine and are not mutually exclusive.

The discharge current Id can be controlled, preferably by the control module 130, in order to keep the current temperature Tc of the battery 120 substantially constant or raise the current temperature Tc of the battery 120 to e.g. the second temperature threshold TT2. The discharge current Id can be controlled either by changing the load impedance ZL by having the load impedance ZL configured to be a variable impedance. Such variable impedances are known and readily available on the market. Alternatively, and preferably, the discharge current Id is controlled by pulse width modulation, PWM, of the control signal(s) controlling the connection of the load impedance ZL to the battery 120. In practice, this may be achieved by applying PWM control to the switches Si-3 of Figures 5a-c, or PWM control of switches controlling the electric motor 110 if the electric motor 110 is the load impedance ZL.

With reference to Figure 6, a method 200 of heating a battery 120 will be explained. The battery 120 is arranged in an entrance system 10 for providing power to one or more electric motors 110 of the entrance system 10. As previously explained, the battery 120 may be the sole source of power for the entrance system 10, used as a backup source of power, or provided to source high currents for the electrical motor(s) 110. The method 200 may be executed by the control module 130 of the entrance system 10. The method 200 may be configured to control, perform and/or monitor any features listed throughout this disclosure.

The method 200 is based on monitoring 210 the current temperature Tc of the battery 120 and the state of charge SOCc of the battery 120. Periodically or continuously during the monitoring 210, the current temperature T_c is compared 215 to the first temperature threshold TTI and the current state of charge SOCc is compared 215 to the first charge threshold Tsoci. If the current temperature T_c of the battery 120 is below the first temperature threshold TTI and the current state of charge SOCc is below the first charge threshold TTI, the method 200 executes the step of discharging 220 the battery 120 by means of the load impedance ZL. During the discharging 220, the current temperature T_c is compared 225 to the second temperature threshold TT2, and if the current temperature T_c is above or equal to the second temperature threshold TT2, the discharging is stopped.

The discharging 220 may be performed by controlling e.g. the switches S1-3 of Figures 5a-c in order to electrically connect the load impedance ZL to the battery 120 and electrically disconnect the electric motor 110 from the battery 120.

In one embodiment of the method 200, after the step of discharging 220, the method 200 is restarted by resuming, if it was stopped, the monitoring 210 the current temperature T_c of the battery 120 and the state of charge SOCc of the battery 120.

In one embodiment of the method 200, the load impedance ZL is the same impedance that is used to dissipate power generated by the electric motor 110 when the electrical motor returns to its idle state. That is to say, the load impedance ZL is further configurable to be arranged to dissipate power generated by said one or more electric motors 110.

The discharging may further comprise controlling 227 the discharge current I_d flowing through the load impedance ZL. This controlling 227 is preferably done, as previously explained, by means of PWN control of the signals controlling the discharging 220. If the electrical motor 110 is used as the load impedance ZL, the discharge current Id is preferably controlled 227 such that the electrical motor 110 is not operated.

In one embodiment of the method 200, the load impedance ZL is the electrical motor 110 as previously explained. This means that there will be no requirement for external load impedances and the method may be implemented in a control module 130 without having to make any hardware modifications to the entrance system 10.

The step of monitoring 210 and/or comparing 215 may further comprise monitoring the time derivative of current temperature T_c. If the time derivative of current temperature T_c. is below the temperature derivative threshold, i.e. if the current temperature T_c of the battery 120 drops at a rate that is below the temperature derivative threshold, the method 200 may be configured to perform the step of discharging 220 the battery 120. Further to this, the step of monitoring 210 may further comprises monitoring the exterior temperature as previously explained. If the exterior temperature is below the exterior temperature threshold, the method 200 may be configured to perform the step of discharging 220. The step of discharging 220 may in this case be configured such that the discharge current Id is controlled such that the current temperature T_c of the battery 120 is kept substantially constant.

In a preferred embodiment of the method 200, the method 200 further comprises the step of charging 230 of the battery 120. The step of charging 230 is executed if the current temperature T_c of the batter 120 is above the second temperature threshold TT2, and the current state of charge SOCc is below the second charge threshold Tsoc2. The charging 230 is preferably performed until the current state of charge SOCc of the battery 120 is above the third charge threshold TT3. Albeit many embodiments and features of the invention have been described such that the current state of charge SOCc of the battery 120 is to be increased by increasing the current temperature T_c of the battery 120, it should be understood that the step of charging 230 in the method 200 and the charging module 135 of the control module, are preferred embodiments.

Claims

1. A method (200) of heating a battery (120), wherein the battery (120) is arranged in an entrance system (10) for providing power to one or more electric motors (110) of the entrance system (10), the method comprising: monitoring (210) a current temperature (T_c) of the battery (120) and a current state of charge (SOCc) of the battery (120), and if the current temperature (T_c) of the battery (120) is below a first temperature threshold (TTI) and the current state of charge (SOCc) of the battery (120) is below a first charge threshold (Tsoci), discharging (220) the battery (120) by means of a load impedance (ZL) until the current temperature (T_c) of the battery (120) is above a second temperature threshold (TT2).

2. The method (200) of claim 1, wherein the load impedance (ZL) is further configurable to be arranged to dissipate power generated by said one or more electric motors (110).

3. The method (200) of any of the preceding claims, wherein the step of discharging (220) comprises controlling (227) one or more switches (Si, S2, S3) to electrically connect the load impedance (ZL) to the battery (120) and electrically disconnect said one or more electric motors (110) from the battery (120).

4. The method (200) of claim 1, wherein the load impedance (ZL) is one or more of said one or more electric motors (110) of the entrance system (10) and the step of discharging (220) further comprises controlling (227) a discharge current (I_d) flowing through said one or more electric motors (110) such that said one or more electric motors (110) are not operated.

5. The method (200) of any of the preceding claims, wherein the step of discharging (220) further comprises controlling (227) the discharge current (I_d) flowing through the load impedance (ZL), preferably by means of PWM control of one or more switches (Si, S2, S3) arranged to connect and disconnect the load impedance (ZL) from the battery (120).

6. The method (200) of any of the preceding claims, wherein the step of monitoring (210) further comprises monitoring (217) a current temperature time derivative of the current temperature (T_c) of the battery (120) and if the current temperature time derivative is below a temperature derivative threshold, performing the step of discharging (220) the battery (120).

7. The method (200) of any of the preceding claims, wherein the step of monitoring (210) further comprises monitoring an exterior temperature, wherein the exterior temperature is external to the battery (120), and if the exterior temperature is below an exterior temperature threshold, performing the step of discharging (220) the battery (120).

8. The method (200) of any of the preceding claims, further comprising, if the current temperature (T_c) is above the second temperature threshold (TΉ), and the current state of charge (SOCc) is below a second charge threshold (Tsoc2): charging (230) the battery (120) until the current state of charge (SOCc) of the battery (120) is above a third charge threshold (Tsoc3).

9. The method (200) of claim 8, wherein the third charge threshold (Tsoc₃) is lower than a maximum state of charge (SOCMAX) of the battery (120), preferably lower than 95 % of the maximum state of charge (SOCMAX) of the battery (120).

10. An entrance system (10) comprising one or more electric motors (110), a load impedance (ZL), a controller module (130) and a battery (120) connectable to provide power to said one or more electric motors (110), wherein the control module (130) is configured to: monitor a current temperature (T_c) of the battery (120) and a current state of charge (SOCc) of the battery (120), and if the current temperature (T_c) of the battery (120) is below a first temperature threshold (TTI) and the current state of charge (SOCc) of the battery (120) is below a first charge threshold (Tsoci), discharge the battery (120) by means of the load impedance (ZL) until the current temperature (T_c) of the battery (120) is above a second temperature threshold (TT2).

11. The entrance system (10) of claim 10, further comprising one or more switches (Si, S2, S3) to electrically connect the load impedance (ZL) to the battery (120) and electrically disconnect said one or more electric motors (110) from the battery (120).

12. The entrance system (10) of claim 10 or 11, wherein the load impedance (ZL) is further connectable to dissipate power generated by said one or more electric motors (110).

13. The entrance system (10) of claim 10, wherein the load impedance (ZL) is one or more of said one or more electric motors (110), and the control module (130) is further configured to control, when discharging the battery (120) by means said one or more electric motors (110), a discharge current (Id) flowing through said one or more electric motors (110) such that said one or more electric motors (110) are not operated.

14. The entrance system (10) of any one of claims 10 to 13, further comprising a charging module (135) and the control module (130) is further configured to, if the current temperature (T_c) is above the second temperature threshold (TT2), and the current state of charge (SOCc) is below a second charge threshold (Tsoc2): charge the battery (120) until the current state of charge (SOCc) of the battery (120) is above a third charge threshold (Tsoc3).

15. The entrance system (10) of claim 14, wherein the third charge threshold (Tsoc3) is lower than a maximum state of charge (SOCMAX) of the battery (120), preferably lower than 95 % of the maximum state of charge (SOCMAX) of the battery (120).