Prediction-based battery swap charge control at pre-charged battery level

Abstract

A method and system for controlling the charging of a plurality of batteries at a battery exchange station is provided. The method includes predicting a need for fully charged batteries and adding a safety margin to determine an initial number of fully charged batteries at a given time, and setting a lower threshold for the number of fully charged batteries at a given time. The method includes charging the plurality of batteries to a full charge level to provide the initial number of fully charged batteries, and a further step of charging the plurality of batteries to at least a first pre-charge level, where the first pre-charge level is a lower state of charge than the full charge level. The method further includes comparing the threshold with the actual number of fully charged batteries, and replenishing the number of fully charged batteries by charging at least some of the batteries from the first pre-charge level to the full charge level.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to prediction-based battery exchange charging control at a battery exchange station.The present invention provides a method, system, computer program, and recording medium for charging control of multiple batteries at a battery exchange station. [Background technology]

[0002] One of the causes of environmental pollution is vehicle exhaust fumes. Electric vehicles are a promising solution to curb vehicle exhaust fumes. The recent development of electric vehicles (EVs) has increased the need to regularly charge the batteries for electric vehicles. Direct charging of electric vehicles is very common to replenish the batteries, but it is time-consuming. As an alternative, battery swapping is a quick solution to replenish the energy of electric vehicles.

[0003] Battery swap stations allow electric vehicles to exchange their partially or fully discharged batteries for fully charged ones. The returned batteries can be charged at the station and later given to other EVs. This reduces the problem of long charging times, as the EV can be used while the battery is charging. Public battery swap stations typically contain multiple batteries and serve multiple customers. Because the batteries are typically owned by the swap station operator, not the EV driver, maintenance costs resulting from battery degradation can account for a large portion of the swap station's operating costs.

[0004] Generally, charging and discharging batteries leads to battery degradation, which means that their capacity decreases over time. Even in idle states, batteries degrade over time, a process usually called calendar aging. This degradation increases with the battery's state of charge (SOC). Therefore, when batteries are charged at a battery exchange station, ideally, they should be charged as late as possible. This means that they will never have an SOC higher than that required to satisfy all user demands. However, the problem is that the exact future demand is unknown, i.e., it is usually unknown when users will need a full battery. A typical way to address this problem is to charge batteries based on a prediction of future replacement demand. To account for the uncertainty of the prediction, we typically calculate not only the mean or forecast value of the demand at time step t, but also the corresponding standard deviation σ t The time step may be, for example, one hour. The predicted mean and standard deviation are then μ t +X*σ t batteries are considered by ensuring they are fully charged at the beginning of time step t using a predefined parameter X. It can be assumed that switching station operators are typically interested in high quality service levels and therefore prefer a conservative setting (i.e., a high value) for X. A high value for X means that significantly more batteries will be fully charged than needed most of the time, leading to unnecessarily high battery degradation.

[0005] Traditional approaches to controlling the charging process at battery exchange stations consider uncertainty. A robust, or stochastic, optimization approach is to compute a charging plan that is optimal with respect to an average or worst-case objective over multiple future scenarios. Another approach is to model charging under uncertainty as a Markov decision process (MDP) and solve the MDP with approaches such as dynamic programming, heuristics, or reinforcement learning. These approaches typically consider uncertainty in future exchange demand as well as uncertainty in other operating conditions, such as future energy prices. Furthermore, they typically plan battery charging multiple time steps ahead. Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an object of the present invention to provide a method for controlling the charging of multiple batteries at a battery exchange station in such a way that fewer batteries are fully charged while still providing a high quality of service. It is also an object of the present invention to provide a system for controlling the charging of multiple batteries at a battery exchange station. A further object is to provide a computer program and a computer-readable storage medium for controlling the charging of multiple batteries at a battery exchange station. [Means for solving the problem]

[0007] To solve the above problems, a method according to the first independent claim, a system according to the second independent claim, a computer program according to the third independent claim, and a computer-readable recording medium for the same purpose according to the fourth independent claim are provided.

[0008] According to a first aspect of the present invention, there is provided a method for controlling charging of a plurality of batteries at a battery exchange station. The method includes predicting a need for fully charged batteries and adding a safety margin to determine an initial number of fully charged batteries at a given time, and setting a lower threshold for the number of fully charged batteries. The method includes charging the plurality of batteries to a full charge level to provide the initial number of fully charged batteries, and a further step of charging the plurality of batteries to at least a first pre-charge level, the first pre-charge level being a lower state of charge than the full charge level. The method further includes comparing the threshold with the actual number of fully charged batteries, and replenishing the number of fully charged batteries by charging at least some of the batteries from the first pre-charge level to the full charge level.

[0009] The method of the present invention employs pre-charge levels to reduce the average SOC of batteries at the exchange station while still being able to meet user demand with a high probability, thereby requiring fewer fully charged batteries. At least one pre-charge level ensures that additional fully charged batteries are available within a short period of time when the number of fully charged batteries falls below a threshold. A safety margin of fully charged batteries is advantageously added to the required (average) amount of fully charged batteries so that when demand exceeds the predicted number of fully charged batteries needed at a given time, the exchange station still has additional fully charged batteries available to meet demand. However, the safety margin may be significantly smaller than in conventional systems. When a battery exchange station runs out of fully charged batteries and a replacement demand occurs (as indicated by the threshold), batteries can be charged to a fully charged state from a first pre-charge level to meet the demand. Additional fully charged batteries are available during the time required to fully charge a battery from the first pre-charge level. Having batteries at the first pre-charge level allows the exchange station to replenish its inventory of fully charged batteries without significantly impacting battery life. Furthermore, when the number of fully charged batteries at a given time falls below a threshold, the exchange station responds by charging batteries from a first pre-charge level to full charge to meet or exceed the threshold. For example, the SOC of the first pre-charge level may preferably be 95% SOC, 90% SOC, or 85% SOC. The SOC of the first pre-charge level may vary from these exemplary values. Other values ​​may be suitable.

[0010] Preferably, the method further includes charging a plurality of batteries to a second pre-charge level that is a state of charge lower than the state of charge of the first pre-charge level, and replenishing the number of batteries charged to the first pre-charge level as the batteries are charged from the first pre-charge level to a fully charged level. By having several batteries charged to different pre-charge levels, unexpected demand for fully charged batteries can be met quickly. Battery degradation can be avoided or at least reduced because fewer batteries are maintained in a fully charged state at the battery exchange station. Furthermore, the number of batteries at the first pre-charge level can also be reduced, resulting in a further reduction in the aging of the number of batteries. When demand is higher than expected, batteries from the second pre-charge level are used to compensate for the number of batteries fully charged from the first pre-charge level.

[0011] Preferably, the method further includes charging the plurality of batteries from the second pre-charge level to a third pre-charge level, the third pre-charge level being at a charge level below the second pre-charge level and being used to replenish the second pre-charge level when the plurality of batteries are used to replenish the first pre-charge level. More preferably, a fourth pre-charge level and / or additional pre-charge levels are maintained at the battery exchange station. The SOC of each pre-charge level is lower than that of the previous pre-charge level and higher than that of the subsequent pre-charge level. The batteries at each pre-charge level are used to replenish the inventory of the previous (higher) pre-charge level. Maintaining batteries at multiple pre-charge levels allows for rapid replenishment of fully charged batteries when the number of available fully charged batteries falls below a threshold, thereby providing a high-quality service level to customers without degrading batteries at the battery exchange station. Using such a hierarchy of charge levels reduces the overall aging of the batteries while simultaneously ensuring the availability of fully charged batteries within a short period of time. Thus, it is possible to take advantage of the time to exchange additional fully charged batteries to replenish the reserve, simultaneously a battery at a first pre-charge level, a battery at a second pre-charge level, etc. Note that this effect is already present for a single, first pre-charge level, and is further improved by increasing the number of different charge levels.

[0012] Preferably, the method periodically determines the required amount of fully charged batteries and / or the safety margin. Advantageously, the inventory of fully charged batteries is periodically updated.

[0013] Preferably, the method allows the threshold to be preset by a user and / or calculated based on historical data. Advantageously, the data may be based on week, holiday season, weekend, charging station location, or a combination thereof. Thus, the method according to the present invention allows for meeting customer needs by monitoring customer movements over time.

[0014] According to a second aspect of the present invention, a system for controlling the charging of a plurality of batteries at a battery exchange station is provided. The system includes a prediction module configured to predict a need for fully charged batteries and add a safety margin to determine an initial number of fully charged batteries at a given time. The system further includes a charge manager module configured to receive, for example, a threshold value for the number of fully charged batteries at a given time from an operator. The system further includes a charge manager configured to receive the predicted need for fully charged batteries from the prediction module and compare the threshold value with the actual number of fully charged batteries. The charge manager is further configured to replenish the number of fully charged batteries, at least in part, by charging batteries from a first pre-charge level to a fully charged level. This is achieved by the charge manager instructing the control and monitoring module to charge the plurality of batteries to a fully charged level to provide an initial number of fully charged batteries, and to charge the plurality of batteries to at least the first pre-charge level, the first pre-charge level being a charge state lower than the fully charged level. Thus, all decisions regarding charging strategy, timing, and determining the required number of batteries to which charge level are made by the charge manager. The charge manager only needs to be in communication with the control and monitoring module, which is instructed by the charge manager to actually perform the charging of the batteries according to decisions made by the charge manager. The system is capable of implementing the method of the first aspect at a battery exchange station. Advantageously, the system is simple and easy to implement, while significantly reducing degradation of multiple batteries.

[0015] Preferably, the control and monitoring module of the system is configured to obtain the actual number of fully charged batteries, the state of charge of the plurality of batteries at the exchange station, and / or the serial numbers of the plurality of batteries at the exchange station. Furthermore, the control and monitoring module may also record battery temperature, charge rate, and / or discharge rate. For example, new batteries may have a higher replacement priority than older batteries because they have fewer charge cycles. Thus, the overall life expectancy of all batteries at the exchange station may be optimized. This in turn allows for the prediction of the battery life expectancy. Therefore, batteries at the exchange station may be distributed to an appropriate pre-charge level or replaced based on their life expectancy.

[0016] Preferably, the system includes a logging module configured to periodically receive from the control and monitoring module the actual number of fully charged batteries, a threshold value, the state of charge of the plurality of batteries at the exchange station, and / or the serial numbers of the plurality of batteries at the exchange station. The logging module may receive and record battery temperature, charge rate, and / or discharge rate from the control and monitoring module. The logging module is further configured to store the received information over a period of time in a database. Advantageously, this allows tracking of battery life, performance, and charge / discharge rate of each battery.

[0017] Preferably, the charge manager is configured to receive the state of charge of the plurality of batteries from the control and monitoring module or the logging module.

[0018] Preferably, the charge manager is configured to charge the plurality of batteries to a second pre-charge level that is a state of charge lower than the state of charge of the first pre-charge level. Optionally, the charge manager is configured to replenish the number of batteries charged to the first pre-charge level when the batteries are charged from the first pre-charge level to the fully charged level. Similarly, a third pre-charge level, a fourth pre-charge level, and possibly further battery levels may also be employed in the system to establish a system with a hierarchy of charge levels. The SOC of each additional pre-charge level is lower than the previous (existing) pre-charge level, i.e., the third pre-charge level has a lower SOC than the second pre-charge level, the fourth lower than the third, etc. Advantageously, the batteries are charged to different pre-charge levels, allowing only the required number of batteries to be fully charged at a given time. This helps improve battery life expectancy. The batteries are charged stepwise to the next higher charge level.

[0019] Preferably, the logging module, the prediction module, and / or the charging manager module are internal or external to the exchange station. Furthermore, the logging module, the prediction module, and / or the charging manager module may be in the form of a cloud service.

[0020] According to a third aspect of the present invention, there is provided a computer program for carrying out the method of the first aspect of the present invention, wherein the computer program is configured to control charging of a plurality of batteries at a battery exchange station according to an inventive method comprising: predicting a required number of fully charged batteries and adding a safety margin to determine an initial number of fully charged batteries at a given time; setting a lower threshold for the number of fully charged batteries; charging the plurality of batteries to a full charge level to provide the initial number of fully charged batteries; charging the plurality of batteries to at least a first pre-charge level, the first pre-charge level being a lower state of charge than the full charge level; comparing the threshold with the actual number of fully charged batteries; and replenishing the number of fully charged batteries, at least in part, by charging the batteries from the first pre-charge level to the full charge level.

[0021] According to a fourth aspect of the present invention, there is provided a computer-readable recording medium having recorded thereon the computer program according to the third aspect.

[0022] Exemplary embodiments of the present invention will now be further described, by way of example only and not by way of limitation, with reference to the drawings in which: [Brief explanation of the drawings]

[0023] [Figure 1] 3 shows an exemplary flow chart of a method for controlling charging of multiple batteries at a battery exchange station according to the present invention. [Figure 2] 1 illustrates an exemplary embodiment of a schematic diagram of a battery with pre-charge levels at a battery exchange station in accordance with the present invention. [Figure 3] 1 illustrates an exemplary embodiment of a system for controlling the charging of multiple batteries at a battery exchange station according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. However, the following embodiments of the present invention may be modified, and the scope of the present invention is not limited by the following embodiments. Reference numerals for similar entities in different embodiments are partially omitted, but still refer to the same elements or features.

[0025] 1 shows an exemplary embodiment of a method according to a first aspect of the present invention as a flowchart. The method illustrates the main steps of controlling charging of a plurality of batteries at a battery exchange station according to the present invention. The method includes the steps of: (S1) predicting the required number of fully charged batteries to determine an initial number of fully charged batteries at a given time and adding a safety margin; (S2) setting a lower threshold for the number of fully charged batteries; (c) charging the plurality of batteries to a full charge level to provide an initial number of fully charged batteries, and (S3) charging the plurality of batteries to at least a first pre-charge level, where the first pre-charge level is a lower state of charge than the full charge level; (S4) comparing the threshold with the actual number of fully charged batteries; and (S5) replenishing the number of fully charged batteries, at least in part, by charging batteries from the first pre-charge level to the full charge level, when the actual number of fully charged batteries is below the threshold.

[0026] Optionally, if the actual number of fully charged batteries is greater than or equal to the threshold in step S4, the system repeats step S4, and if the number of fully charged batteries is less than the threshold, the system repeats step S5 for a preset time, after which the system returns to step S1.

[0027] To avoid battery degradation, only the necessary (estimated) number of batteries, plus a safety margin, are fully charged. Therefore, an unnecessary number of fully charged batteries are prevented from being stored for a longer period of time. If demand causes the number of fully charged batteries to fall below a threshold, the battery exchange station must be able to replenish the number of fully charged batteries as quickly as possible. A threshold for fully charged batteries at a given time is set. Batteries at least at a first pre-charge level are maintained in the battery exchange station to at least partially replenish the actual number of fully charged batteries when the need arises. For example, the first pre-charge level may be set to a 95%, 90%, or 85% state of charge. Generally speaking, the first pre-charge level may be set to any state of charge less than 100% state of charge. Batteries at a second pre-charge level, a third pre-charge level, and / or further pre-charge levels may be maintained in the battery exchange station. Each pre-charge level has a lower SOC than the previous (higher) pre-charge level. The intervals between charge levels may be selected to be the same or different, for example, to be larger for each additional (lower) pre-charge level.

[0028] The charging of the battery at the station may be controlled at least in an on / off state, which means that the battery is charged to a certain maximum power p max This means that the battery may be charged at 0 kW or at zero kW power (the battery is idle). This does not exclude that a battery exchange station may allow control with more than these two power levels.

[0029] Furthermore, without loss of generality, it is assumed that only batteries with a 100% SOC can be delivered to customers. The described approach can be easily adapted if batteries can be delivered once their SOC exceeds some value less than 100%.

[0030] Time is discretized into time steps of equal length Δt (e.g., 1 hour), and it is possible to charge the battery from 0% SOC to 100% SOC within the range of Δt time units. Each time step is further discretized into sub-steps of length Δτ (e.g., 1 minute). According to the invention, managing the charging of the battery at time step t is based on the respective average values μ t and μ t+1 as well as the standard deviations σ t and σ t+1 of the number of exchanges in the current time step and the next time step.

[0031] It is proposed to adopt a pre-charge level in order to reduce the average SOC of the batteries at the exchange station while still being able to satisfy user demand with a high probability. Thereby, fewer batteries are charged from start to full SOC, but backup batteries (for at least one pre-charge level) are maintained at an SOC close to 100% and can be quickly fully charged if necessary.

[0032] The total number of batteries is assigned to M pre-charge levels B1, B2,..., B M , and the batteries at pre-charge level B1 have an SOC of S1 = 100%, the batteries at pre-charge level B2 have an SOC of at least S2 < 100%, the batteries at pre-charge level B3 have an SOC of at least S3 < S2, and so on. It is clear that all the batteries at pre-charge level B i are also at pre-charge level B i+1 .

[0033] In each sub-step τ of time step t, the following control logic is executed. S τ indicates the number of exchanges performed in time step t up to the maximum sub-step τ. The number N 1,τ [[ID=I30]]of batteries at level B1 is N‘ 1,τ = max{μ t - S τ + X1 · (σ t + σ t+1),T}+μ t+1 (1) If less than N', the highest SOC is not level B1 1,τ -N 1,τ batteries start charging (or remain charging, respectively), where X1 and T are predefined parameters. This means that at time steps t and t+1, the total μ t +μ t+1 +X1(σ t +σ t+1 ) battery replacement, and have at least T batteries for replacement at the current time step t and μ for replacement at the next time step t+1. t+1 This means that we want to have N batteries. 2,τ but, N' 2,τ =N' 1,τ +X2(σ t +σ t+1 ) (2) If it is less than N', the precharge level B2 is not the highest SOC. 2,τ -N 2,τ batteries start charging (or remain charging, respectively). Again, X2 is a predefined parameter. In this way, it should be ensured that there are always a sufficient number of batteries that can be quickly charged to level B1, if necessary. The number of batteries at precharge level B2, N 2,τ N' 2,τ If the amount is more than necessary, an unnecessarily high SOC is undesirable, so N with the lowest SOC of B2 2,τ -N' 2,τ The batteries stop charging (or remain idle, respectively) and proceed to the remaining lower levels B3... as well as pre-charge level B2.

[0034] The invention is illustrated by an example: At time step t, μ t +μ t+1 +3·(σ t +σ t+1 ) batteries directly to 100%.t +μ t+1 +σ t +σ t+1 Only batteries are fully charged, and σ t +σ t+1 Additional batteries are charged to 90% SOC, and σ t +σ t+1 additional batteries are charged to 70%. If the number of fully charged batteries becomes low (according to equation (1)), the battery exchange station can respond by charging some of the 90% SOC batteries to 100% SOC and replenish the lower battery levels accordingly.

[0035] Number of precharge levels M, S2, ..., S of SOC M , number X1, ...X M By appropriate setting of parameters such as , and the threshold T, user demand can be met with high probability and the average SOC can be kept lower than with the standard approach. It is proposed to optimize the parameters based on simulations against historical data.

[0036] FIG. 2 shows an exemplary embodiment of a schematic of a battery 200 having different charge states at a battery exchange station for servicing clients. The batteries are classified into charge levels 202, 203, 204, 205, and 206. As an example, a battery exchange station may hold five fully charged batteries 201, three batteries 202 at a first pre-charge level, two batteries 203 at a second pre-charge level, two batteries 204 at a fourth pre-charge level, two batteries 205 at a first pre-charge level, and one battery 206 at a fifth pre-charge level. The different pre-charge levels may correspond to, for example, 90%, 80%, 70%, 60%, and 50%. Note that a charge level does not necessarily mean that all batteries at that charge level actually have the same charge state. A charge level corresponds to a certain minimum SOC. For example, a 90% charge level may correspond to an actual state of charge between 90% and 100%, a 80% charge level may correspond to an actual state of charge between 80% and 100%, etc. It is clear that other intervals may be defined by the respective charge levels.

[0037] When a customer exchanges an empty battery for a fully charged battery at a battery exchange station, and the number of fully charged batteries available at the battery exchange station falls below a threshold, batteries from a first pre-charge level are allowed to be charged to a fully charged state to meet the need for fully charged batteries, thereby replenishing the need for fully charged batteries. The number of batteries at the first pre-charge level is then preferably replenished by charging batteries from a second charge level. Similarly, batteries from a later (next lower) pre-charge level are charged to meet the need for the previous (next higher) pre-charge level. If the threshold number of fully charged batteries is still available after the customer exchanges the empty battery, the battery exchange station repeats steps S4 and S5, as described above, for a preset time or until the next customer transaction. The actual state of each battery at the battery exchange station is periodically monitored. To replenish the next higher charge level, it is preferable to start with the battery with the highest actual charge state among the batteries belonging to the respective charge level from which the higher charge level is being replenished.

[0038] An exemplary embodiment of a system for controlling the charging of multiple batteries at a battery exchange station is shown in FIG. 3. System 300 includes multiple battery slots 301 for receiving batteries. System 300 further includes a control and monitoring module 302, a logging module 303, a prediction module 304, and a charge manager 305. Control and monitoring module 302 is configured to perform charging of the batteries at the battery exchange station based on information received from charge manager 305 and to extract current status information of the stored batteries, such as the battery's state of charge and serial number. Logging module 303 is configured to store the status information over a period of time in a database. Prediction module 304 is configured to generate a prediction of the number of future exchange requests (and therefore the number of fully charged batteries required) based on historical data provided by logging module 303 and send the prediction to programmable charge manager module 305. The prediction may be based on the mean and standard deviation. Charge manager 305 is configured to determine a charging strategy based on the prediction and the current battery status and send a corresponding control signal to control and monitoring module 302, which implements the control.

[0039] Additionally, the control and monitoring module 302 may extract the actual number of fully charged batteries and the state of charge of the plurality of batteries at the exchange station. The logging module 303 may periodically receive the actual number of fully charged batteries, the state of charge of the plurality of batteries at the exchange station, and / or the serial numbers of the plurality of batteries at the exchange station from the control and monitoring module 302. The logging module 303 may store the received information over a period of time in a database. The charging manager module 305 is configured to receive the state of charge of the plurality of batteries from the control and monitoring module 302 or the logging module 303.

[0040] Additionally, the charge manager module 305 is further configured to determine charging the plurality of batteries to a second pre-charge level that is a state of charge less than the state of charge of the first pre-charge level, and to instruct the control and monitoring module 302 to replenish the number of battery charges of the first pre-charge level as the batteries from the first pre-charge level are charged to a full charge level. Additional batteries at additional pre-charge levels may be maintained at the battery exchange station. The number of pre-charge levels varies and may be predetermined or assigned at the exchange station.

[0041] The logging module 303, the prediction module 304, and / or the charging manager module 305 may be internal or external to the exchange station 300. The logging module 303, the prediction module 304, and / or the charging manager module 305 may be in the form of a network-based cloud computing technology, such as a cloud service. The cloud service may be a cloud host for providing cloud management and cloud storage services.

[0042] A further embodiment is remote monitoring of a battery exchange station. The remote monitoring system may include a radio tower, a GPS navigation or other satellite, a cellular communication tower, a wireless router, a remote enabled device, or a remote computer system or server using a wireless data connection or any other remote communication that can be communicated wirelessly via a remote system interface.

[0043] A computer program configured to implement the method according to the present invention in whole or in part may be recorded on a computer-readable recording medium using a computer system. The computer system in this specification includes hardware such as an OS or peripheral devices. The computer-readable recording medium may refer to a portable medium such as a flexible disk, an optical magnetic disk, or a CD-ROM, or a storage device such as a hard disk installed in a computer system. The computer-readable recording medium may also include a medium that retains a program for a certain period of time, such as volatile memory (RAM) in a computer system that is a server or a client when the program is transmitted over a network such as the Internet or a communication line such as a telephone line. In addition, the program may be transmitted from a computer system in which the program is stored to another computer system via a transmission medium or by transmission waves in a transmission medium.

[0044] A discussion of any of the aspects also pertains to other aspects of the invention. While the invention has been shown and described with respect to one or more embodiments, equivalent variations and modifications will occur to others skilled in the art upon reading and understanding this specification and the accompanying drawings. In addition, while certain features of the invention may be disclosed with respect to only one of the embodiments, such features of other embodiments may be desirable and advantageous for any given application or particular use.

Claims

1. 1. A method of controlling charging of a plurality of batteries at a battery exchange station, comprising: Predicting the required number of fully charged batteries and adding a safety margin to determine the initial number of fully charged batteries at a given time (S1); Setting a threshold for the number of fully charged batteries at said given time (S2); charging (S3) a plurality of batteries to a full charge level to provide the initial number of fully charged batteries, and charging the plurality of batteries to at least a first pre-charge level, the first pre-charge level being a state of charge lower than the full charge level; Comparing the threshold value with the actual number of fully charged batteries (S4); replenishing (S5) the number of fully charged batteries, at least in part, by charging the batteries from the first pre-charge level to the fully charged level; A method comprising:

2. charging a plurality of batteries to a second pre-charge level that is a state of charge less than the state of charge of the first pre-charge level; replenishing the number of charges of the battery at the first pre-charge level as the battery is charged from the first pre-charge level to the full charge level; The method of claim 1 further comprising:

3. charging the plurality of batteries to a third pre-charge level that is a charge level less than the second pre-charge level; replenish the second pre-charge level and the third lower pre-charge level when the plurality of batteries from the second pre-charge level and the third pre-charge level are used to replenish a higher pre-charge level. The method of claim 2 further comprising:

4. The method of any one of claims 1 to 3, further comprising periodically determining the fully charged battery requirement and / or the safety margin.

5. The method of any one of claims 1 to 4, wherein the threshold is pre-set by an operator and / or calculated based on historical data.

6. 1. A system for controlling charging of a plurality of batteries at a battery exchange station, comprising: a prediction module configured to predict the required number of fully charged batteries and add a safety margin to determine an initial number of fully charged batteries at a given time; a charge manager module configured to receive from an operator the threshold number of fully charged batteries at the given time; the charging manager module is further configured to receive the predicted required number of fully charged batteries from the prediction module and compare the threshold to the actual number of fully charged batteries; the charge manager module is further configured to replenish the number of fully charged batteries, at least in part, by charging the batteries from the first pre-charge level to the fully charged level; the charging manager module is further configured to instruct the control and monitoring module to charge the plurality of batteries to a full charge level to provide the initial number of fully charged batteries, and to charge the plurality of batteries to at least a first pre-charge level, the first pre-charge level being a lower state of charge than the full charge level.

7. 7. The system of claim 6, wherein the control and monitoring module is configured to extract the actual number of fully charged batteries, the state of charge of the plurality of batteries at the exchange station, and / or the serial numbers of the plurality of batteries at the exchange station.

8. a logging module configured to periodically receive from the control and monitoring module the actual number of fully charged batteries, the state of charge of the plurality of batteries at the exchange station, and / or serial numbers of the plurality of batteries at the exchange station; The system of claim 7 , wherein the logging module is configured to store the received information in a database over a period of time.

9. The system of any one of claims 6 to 8, wherein the charge manager module is configured to receive the charge status of the plurality of batteries from the control and monitoring module or the logging module.

10. 10. The system of claim 6, wherein the charge manager module is configured to charge a plurality of batteries to a second pre-charge level that is a state of charge less than the state of charge of the first pre-charge level, and is further configured to replenish the number of battery charges at the first pre-charge level as batteries are charged from the first pre-charge level to the fully charged level.

11. The system of any one of claims 8 to 10, wherein the logging module, the prediction module, and / or the charging manager module are internal or external to the exchange station.

12. The system of any one of claims 8 to 11, wherein the logging module, the prediction module, and / or the charging manager module are in the form of a cloud service.

13. 1. A computer program configured to control charging of a plurality of batteries at a battery exchange station, the computer program comprising: predicting the required number of fully charged batteries and adding a safety margin to determine the initial number of fully charged batteries at a given time; setting a threshold number of fully charged batteries at said given time; charging a plurality of batteries to a full charge level to provide the initial number of fully charged batteries, and charging the plurality of batteries to at least a first pre-charge level, the first pre-charge level being a state of charge lower than the full charge level; comparing the threshold value with the actual number of fully charged batteries; replenishing, at least in part, the number of fully charged batteries by charging the batteries from the first pre-charge level to the fully charged level; a computer program comprising:

14. A computer-readable recording medium having the computer program according to claim 13 recorded thereon.

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