WO2015103164A1

WO2015103164A1 - Direct current to direct current battery based fast charging system for an electric vehicle charging station

Info

Publication number: WO2015103164A1
Application number: PCT/US2014/072606
Authority: WO
Inventors: Hans VAN DER MEER; Virgil BEASTON; Daniel Williams
Original assignee: Ev4, Llc
Priority date: 2013-12-31
Filing date: 2014-12-29
Publication date: 2015-07-09

Abstract

A battery based DC fast charging system is provided. The system is configured to provide DC fast charging capabilities to an electric vehicle charging station and to recharge the battery system of the charging station by utilizing a renewable energy collection system and single-phase connection to the grid. A user connects an electric vehicle to the charging station and requests a battery recharge. Power is delivered to the electric vehicle by the battery system of the charging station. The battery system is recharged by the renewable energy collection system, and power from the grid.

Description

DIRECT CURRENT TO DIRECT CURRENT BATTERY BASED FAST CHARGING SYSTEM FOR AN ELECTRIC VEHICLE CHARGING STATION

BACKGROUND

[0001] Efforts to reduce our dependence on burning fossil fuels have increased demand for alternative means of generating power, for vehicles in particular. One method includes replacing the gasoline engine of a vehicle with one powered entirely by electricity stored in a battery. However, as electric vehicles become more common, the need for offering regular opportunities to recharge their batteries in a fast mode grows. A typical Direct Current fast charging station (DCFC) routes power from the grid and supplies it as DC power to the connected vehicle, yet, the power supplied by the grid may come from power plants that are just as environmentally harmful as it would be to use a gasoline powered vehicle. Additionally, depending on the time of day, the cost of pulling the demanded power for a speedy recharge from the grid can be unnecessarily high. Also at certain locations, the DC fast charging cannot be delivered due to insufficient power of, or access to, the electrical grid.

SUMMARY

[0002] A direct current battery based fast charging system is provided. The system includes direct current (DC) to DC charging from the batteries to an electric vehicle. The system is configured to provide fast charging capabilities to the electric vehicle and to optionally recharge the battery system of the charging station by utilizing a renewable energy collection system and a single grid connection, such as a simple, 3-wire, single phase connection to the electrical grid. A user connects an electric vehicle to the charging station and requests a battery recharge. Power is routed to the battery of the electric vehicle until it is charged utilizing the battery system of the charging station, power collected by the renewable energy collection system, and power from the grid. In this way, fast charging is provided with a simple grid interface by taking advantage of the battery system in the charging system.

[0003] Additionally, the system is configured to simultaneously provide a slow charge so that the charging station may charge two separate electric vehicles simultaneously. Power for the slow charge may also utilize the battery system of the charging station, power collected by the renewable energy collection system, and power from the grid. In this way, two separate electric vehicles may receive a charge from the same charging station. [0004] This Summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is an example flow chart of power management in an electric vehicle charging station according to the present disclosure.

[0006] FIG. 2 is an example flow chart depicting a system diagram of an electric vehicle charging station.

[0007] FIG. 3 is an example state diagram depicting various system states of an electric vehicle charging station.

[0008] FIG. 4 depicts an example of an EV4 state machine according to the present disclosure.

[0009] FIG. 5 is an example circuit diagram of a battery management system (BMS) according to the present disclosure.

[0010] FIG. 6 depicts an example of a solar powered electric vehicle charging station according to the present disclosure.

DETAILED DESCRIPTION

[0011] Embodiments are disclosed herein that relate to an electric vehicle charging station including a renewable energy collection system and a grid hook-up to supply a battery system configured to charge electric vehicles on request. A fast charging system may be included, where an example of fast charging requires approximately 25 minutes of charge time for a 24 kWh Battery Electric Vehicle (BEV) to charge to 80% capacity from empty. In contrast, level 2 AC chargers may be installed that would generally take 6-7 hours to charge the same vehicle from empty.

[0012] FIG. 1 is a flow chart showing an example of how the system may be implemented. An electric vehicle charging station 100 includes a connection to the grid 102, a DC/ AC power converter 104, one or more batteries 106, and electric vehicle (EV) charging system 108. In addition to those elements, the present disclosure may include energy collection system 110, typically a solar panel array or wind turbine, and a DC/DC charge controller 112. An additional AC/DC battery charger may be provided between battery 106 and the grid 102 for additional charging of the battery system 106, described in more detail below.

[0013] A user may connect their electric vehicle 109 to EV charging system 108 to request a battery recharge, wherein battery 106 discharges to the charging system 108. The battery may be recharged by one or more of the grid 102 and the renewable energy collection system 110. The incoming current to the battery 106 is converted to an appropriate DC voltage to interface with the battery at DC/ AC power converter 104 and DC/DC charge controller 112. When not charging a vehicle, the battery storage system may be used to provide system back up, grid support and load balancing services. Such an arrangement allows an owner to account for and generate revenue through participation in the carbon footprint offset ( EC) markets. It will be noted that the connection to grid 102 uses a 3 -wire single-phase 120/240 VAC hook up. This residential power supply is commonly available and will avoid demand charges for less common power supply voltages. Therefore, charge may travel bi-directionally from battery 106 to grid 102 depending on a charge demand. If the charge demand is present (e.g., the electric vehicle 109 is connected to electric vehicle charging system 108), then charge may flow from grid 102 or energy collection system 110 to battery 106 where it is further directed to flow through the electric vehicle charging system 108 to the electric vehicle 109. Additionally or alternatively, if the charge demand is not present, then the charge may flow from battery 106 to grid 102. The electric vehicle may no longer receive charge upon disconnecting from the electric vehicle charging system 108 or an electric vehicle battery reaching a threshold electric vehicle battery charge. The threshold electric vehicle battery charge may represent electric vehicle battery charge at 90% or greater.

[0014] FIG. 2 depicts an example EV charger system 200 in more detail than that of FIG. 1, with a Level 2 (L2) AC charger and a DC/DC fast charger with the capacity to support the charging of a first EV 206 and a second EV 208, the first EV 206 being slow charged (AC) and the second EV 208 being fast charged (DC) simultaneously. The solar panel structure 210 of the example system is an energy collection system feeding DC to the battery via a load box 212. Alternatively the solar panel structure of the example system may feed back directly to a grid 250 with single phase 120V AC through a net meter 254 and a transformer 252. The grid 250 may supply power to the load box 212 through the transformer 252 and net meter 254. Power supply from grid 250 may be disabled via disconnect 256. With respect to FIG. 2, solid lines represent a power flow and dashed lines represent a transmitted signal from one component to another.

[0015] The load box 212 comprises a circuit breaker 214 that connects a 240VAC/40A output to a L2 AC charger and 100 A to a DC/AC battery charger 216. Therefore, the battery charger 216 may exist between only the circuit breaker 214 and the DC/DC fast charger 204, while the battery charger 216 may not exist between the circuit breaker 214 and L2 AC slow charger 202. In some embodiments, a battery charger may exist between L2 AC slow charger 202 and the circuit breaker 214. The battery charger 216 outputs 50A at 400- 480VDC. The battery charger output is routed either to a battery module 218 to recharge it, or through the DC/DC fast charger 204, which sends a 50 kW output capacity to the second EV 204.

[0016] In some embodiments, the EV charger system may be used to charge a first EV and a second EV. The first EV may utilize the fast charger and the second EV may utilize the slow charger. The first EV and second EV may be charged simultaneously and independently of each other. In other words, a first EV charging condition(s) may not affect a second EV charging condition(s). Likewise, the second EV charging may not affect the first EV charging. Therefore, the first EV and second EV may charge independently of each other.

[0017] In one example, the fast charger may include an internet connected charger controller including a resonant converter module 220. The resonant converter module may be arranged to convert an input voltage into a DC output voltage that will be equal to a battery voltage of the second EV. The input voltage may be a DC voltage or a pulsating DC voltage supplied from the battery bank, as shown. A battery management system (BMS) may control operation 222 of the system 200 by enabling or disabling various elements, including but not limited to the battery charger 216 and the DC/DC fast charger 204 based on feedback from the battery module 218. As an example, the BMS may enable battery charger 216 if an EV is connected to DC/DC fast charger 204 and battery module 218 has a low state of charge (SOC). A low SOC may be defined as a power currently available to a battery that is lower than a charge threshold and may not be able to sufficiently charge an EV battery. The DC/DC fast charger 204 may be powered entirely by the battery module 218 if the battery charger 216 is disabled.

[0018] The battery module may include a plurality of battery packs. The battery packs may each have an amp-hour meter (AHM) and may be arranged in parallel with one another, the batteries within the packs may be arranged in series. For example, a plurality of 6V li-ion batteries may be arranged together to form a pack.

[0019] The solar panel structure may be in the form of a canopy. The solar panels may be used as a power feed for the battery bank in case there is no grid connection, or the grid connection is interrupted. In such a case the solar-generated current may feed the battery system and the battery system will deliver the DC/DC fast charging. The solar panels may be coupled to the top of a charging station.

[0020] In one example of a charging station, steel pipes are cantilevered to support a canopy providing shelter EV drivers from the elements. The station may be equipped with 15 solar panels (4 kW capacity), one DC fast charger and one level 2 (J 1772) charger. Rainwater may be collected, filtered and distributed to the landscaping. Additionally, the charging station may be equipped with a display, such as an LED screen, for advertising purposes.

[0021] The battery management system may be configured to operate based on three distinct inputs, including "Ready", "Demand", and "Full". FIG. 3 depicts a state diagram of the embedded control programming for managing a battery management system (e.g., BMS 222) showing five available system states and the status of the three inputs that would put the system into the given state. The ready (R) input is a composite input indicating the batteries have a state of charge (SOC) greater than a charge threshold and the cells meet balancing criteria. The threshold may be set to the minimum state of charge needed to provide a full quick-charge session. The demand (D) input indicates whether the quick charger is demanding quick-charge current. The demand input, which may be identified via a flag, may be detected when the DC bus AHM senses current over a demand threshold. Note that the condition of demand from the quick charger interface unit will not be detectable when the EnableQC output (EQ) is in the disable state. This is because the opening of the DC bus contactor will render the AHM unable to measure current being drawn by the quick charge unit. This means that in the recover state, the system will not detect the demand input becoming true. This means that when the system is in the recover state, it will deny quick- charge current to the quick charge unit.

[0022] The full (F) input indicates that the SOC may be equal to or greater than a threshold capacity, such as 90%. In other words, F indicates the SOC is near a maximum capacity, while R indicates that the SOC is above the charge threshold. The charge threshold may be lower in value than the threshold capacity (e.g., 25% compared to 90%, respectively). [0023] The available system states include but are not limited to idle 302, discharge 304, recover 306, and top-off 308. The cannot-happen (e.g., unavailable) state 310 includes two combinations of the three input statuses that would not occur during normal operation. As an example, the charge threshold may be lower than 90% of the battery's capacity, thus the system state cannot be both "full" and not "ready". Each of the provided states has a defined output response that determines the behavior of the system while the state persists, where each of those behaviors is configured to meet a behavior goal. For example, system behavior goals may include: (i) responding to a demand from the quick charger to source current if the batteries are sufficiently charged, (ii) denying the demand from the quick charger if the batteries are not sufficiently charged, (iii) charging the batteries if a quick charge is not in progress and the battery state is below a charge threshold, (iv) protecting the system from damage caused by overcharging or undercharging any battery cell, and (v) maintaining balancing criteria.

[0024] As an example, idle 302 represents a dormant state, with the inputs indicating that the battery is neither discharging, nor recharging, as shown by D is equal to "0". Additionally or alternatively, the idle state may include a SOC being greater than or equal to a charge threshold and no input is received from an EV (e.g., no charge demand). Discharge 304 occurs at three separate input combinations, in each case instructing the battery to source a current to fulfill a user request. One example input combination may include R, D, and F being equal to "1", wherein the battery system is ready to discharge power, there is a demand for discharge (e.g., an EV plugged into the discharge station), and the battery SOC is full. Additionally or alternatively, enable grid (EG) may be equal to "1" when F is equal to "0", signifying the battery SOC is below the charge threshold and grid power may be used to charge the EV. Upon unplugging the EV from the charging station (e.g., D is equal to "0"), the battery SOC may fall below the charge threshold (e.g., both R and F are equal to "0"), then the BMS may signal to enter the recover state 306. Recover 306 occurs after discharge 304, allowing the battery to recharge in preparation for the next demand session. During the recover state 306, requests to begin discharging current are denied. In other words, the battery SOC is too low to provide a charge to an EV even if a value of D changes to be equal to "1". This restriction is indicated by an output, EnableQC (EQ), being given a "0" value. In all other states, EQ is equal to "1", meaning the quick charger is enabled. In one example, the battery may be charged with grid power (e.g., EG is equal to "1"). Additionally or alternatively, the battery may be recharged with a renewable energy collection system. The renewable energy collection system may comprise of one or more of solar cells and a wind turbine. Once the battery is "ready", the system state moves on to top-off 308. Top-off 308 represents a state where the battery is continuing the recharging process started in recover 306, but will interrupt the recharging process to begin discharging current if requested. The interruption may be allowed because the SOC of the battery is greater than the charge threshold, although being less than the threshold capacity. If no request is received, charging may continue until the battery is determined to be "full" (e.g., SOC greater than the threshold capacity). The top-off state may be terminated and enter the discharge state if an EV plugs into the charging station and demands charge. Additionally or alternatively, the top-off state may be terminated if the SOC reaches the threshold capacity.

[0025] In this way, the battery management system (BMS) may provide different operation under different conditions. The operations described above may be programmed via code stored in non-transitory memory of the BMS, working together with a processor so that the various actions may be carried out.

[0026] In one example, the BMS includes embedded programming without any inputs from a user or a user interface. For example, only three inputs may be used with only five potential states, as described above with regard to FIG. 3. The system can (1) respond to a demand from the vehicle quick charger interface to source up to 100 Amps of current only if the batteries are sufficiently charged, such as greater than a charge threshold. Further, the system may (2) deny the demand request otherwise after completion of a prior demand session. The system can (3) charge the batteries only if a quick charge is not in progress and the battery state of charge is below a threshold, such as 90%. The system can (4) reduce potential for damage caused by overcharging or undercharging any individual battery cell in the pack(s) of the battery system. Finally, the system can (5) maintain balancing criteria during demand sessions or the idle condition by transferring current among the battery packs.

[0027] A state diagram such as described below with respect to FIG. 4 may be used in place of, or in addition to, the diagram of FIG. 3. The state diagram may be determined by a set of inputs. Thus, the inputs and outputs are described first. In this context, the control system and BMS may have the following features:

HiThresh(H) True when a cell voltage has exceeded the High Cell Voltage Threshold

Outputs

Output Name Description

EPCC A TRUE value will close the contactor that connects the AC to DC charger

(battery charger, where the battery charger may be any suitable battery charger, such as, but not limited to, an EPC battery charger, a Powin battery charger, an ABB battery charger, etc.) to the Battery DC output rail

ABBC A TRUE value will close the contactor that connects the battery DC output rail to the Quick Charger converter

EPCI A current limit value sent to the battery charger

EPCE An enable signal sent to the battery charger

TABLE. 1

[0028] The state diagram may have the following states and features. With 3 inputs, the state diagram includes 8 possible states. Only 4 of these possible states are used to represent system behavior. From any given state, a change of an input variable may cause a transition to another state. Each state has a name consistent with its conceptual function. For example, state DEH = 000 is called the IDLE state 402 because the outputs associated with this state indicate the system may be only idling. Similarly, the DISCHARGE state 404 has outputs that allow the quick charger to fulfill a user request for a charging session, causing the battery system to discharge. The RECOVER state 406 may allow the system to recharge or recover after a quick charge session. Finally, the RELAX state 408 is a state where the system may momentarily stop re-charging the batteries to allow the cells voltages to relax after the High Cell Voltage Threshold has been exceeded. This may be to prevent the battery from overcharging. Overcharging the battery may lead to battery degradation such as battery threshold capacity decreases, dendrite formation, and/or battery fires.

[0029] It should be appreciated that in the below EV4 State Machine example, the ABB Contactor may be any suitable contactor and the ABB Contactor is used for example purposes. Further, the EPC Contactor may also be any suitable contactor and the EPC Contactor is use for example purposes. Similarly, the EPC Charger is used as an example battery charger and other suitable battery chargers may be used without departing from the scope of the disclosure. While some of the state variables are described above, various additional states may be used. [0030] FIG. 5 is a circuit diagram representing a working diagram of an example battery management system 500 that may be used in the system of FIG. 2. The positive 502 and negative 504 power ports are configured to connect to the electric vehicle to be charged by a battery string 506. The main BMS may use various detection methods to determine the condition of the system in order to determine the appropriate system state. Such methods may include detecting the current 510, voltage 512, temperature 514, and leakage 516. The current may be measured with current measuring device 511. The voltage and temperature detect may respectively determine the voltage and temperature of the battery. The leakage detect may monitor if the battery is leaking power/charge. If any of these detections are below a respective threshold, then the BMS may signal a battery degradation and activate an indicator lamp. A control area network (CAN) bus 518 may be used to send control messages to the rest of the system. In one example, the messages received may include at least one command to specify the current limit for the charger. In another example, the battery stack voltage is maintained by the BMS between 400 to 450VDC. The battery voltage may clamp the voltage of the DC rail feeding the charger to limit maximum voltage.

[0031] FIG. 6 illustrates additional details of the system. Specifically, description is provided of the battery management system (BMS) 602, which may include battery packs, control circuit boards, relay switching elements and embedded control programming.

[0032] Another representation of the system described herein is shown in the diagrams below, including a battery charger unit 604 and battery stack 606. The unit 604 may be used in the system that performs the function of an Electric Vehicle Charging Station (EVCS). As described herein, the EVCS uses batteries 606 to supplement or replace the current supplied by the charger 604 during a quick charge session. When the system is not performing a quick charge, the battery charger 604 is used to re-charge the battery stack 606. Therefore, power from the battery charger 604 may flow to either the battery stack 606 or to an EV quick charger pedestal 608. The EV quick charger pedestal 608 may be similar to the electric vehicle charging system 108, with respect to FIG. 1. The battery stack may either receive charge from battery charger 604 or output power to EV quick charger pedestal 608. EV quick charger pedestal 608 may transfer power to an EV battery 610. The EV battery 610 may stop receiving power by either a disconnection between the EV battery 610 and the EV quick charge pedestal 608 or the EV battery 610 reaching a threshold EV SOC.

[0033] It will be noted that the battery system may optionally be used as a UPS for businesses or residences. It will also be noted that a DC only system may be configured to use only DC inputs such as solar and wind, wherein no AC/DC power conversion takes place. The system may be configured to utilize CHAdeMO, Tesla, and SAE standards. For example, the output of the charge controller may be in the CHAdeMO format.

[0034] In one example, the system described herein can be operated to provide fast DC charging without a specialized hook-up to the electrical grid while still enabling a minimum 50 kW power to charge the electric vehicle. Normally, only a "residential" single phase 240 VAC can be utilized with no demand charge on the grid.

[0035] The system may further include a user interface with code stored in memory and working with a processor for adjusting the various interfaces, chargers, etc., and may be connected to the internet so that various additional features may be provided, including billing and tracking of credits and charges, etc. In one example, code may be included for enabling consumers to quantify, validate, store and use renewable energy to charge their electric vehicle. The owner may thus account for and generate revenue through participation in a carbon footprint offset market, if desired.

[0036] In one example, the battery management controller and battery packs may be configured as described in U.S. Patent No. 20130328530, which is incorporated herein by reference in its entirety. In this example, each battery pack has battery cells, a battery pack controller that monitors the cells, a battery pack cell balancer that adjusts the amount of energy stored in the cells, and a battery pack charger. The battery pack controller operates the battery pack cell balancer and the battery pack charger to control the state-of-charge of the cells.

[0037] While some of the state variables are described above, various additional states may be used.

[0038] In this way, by including a slow charging and fast charging capability in a charging station, two separate electric vehicles may receive an electric charge from the charging station independent of one another. In other words, the charging of one electric vehicle does not affect the charging of a separate electric vehicle. Further, the charging station may provide a charge via three separate power sources including but not limited to a charging system battery, a renewable energy collection system, and a grid. During instances when a charge demand is not recognized by the charging station (e.g., an electric vehicle is not plugged in), the charging station may return power to the grid.

[0039] The technical effect of providing a charging station with power from a renewable energy collection system and a grid is to allow the charging station to charge two separate electric vehicles simultaneously. Additionally or alternatively, the charging station may be able to provide power back to the grid when an electric vehicle is not connected to the charging station.

[0040] The following claims particularly point out certain combinations and subcombinations regarded as novel and non-obvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

CLAIMS:

1. A method for managing a battery system in an electric vehicle charging station, the method comprising:

receiving a request to recharge a battery in an electric vehicle connected to the electric vehicle charging station;

outputting a first DC current from the battery system through a battery charger to recharge the battery in the electric vehicle with a second DC current; and

recharging the battery system using one or more of a renewable energy collection system and a grid directly coupled to the electric vehicle charging station.

2. The method of claim 1 wherein the first DC current from the battery system is converted to a second DC current via a charge controller, and wherein the battery system is selectively charged via grid power only through a single phase 240 VAC and without a 3- phase 480 VAC from the grid.

3. The method of claim 1, wherein the electric vehicle charging station provides a fast charging current to a first electric vehicle and a slow charging current to a second electric vehicle simultaneously, and wherein the first electric vehicle and the second electric vehicle are charged independently of each other.

4. The method of claim 3, wherein recharging the battery system using a renewable energy collection further includes converting the renewable energy collection system into a selected DC voltage via a DC/DC charge controller.

5. The method of claim 1, wherein the recharging further comprises two modes:

during the first mode, a DC/DC fast charger is used to charge the electric vehicle; and during the second mode, a DC/ AC slow charger is used to charge the electric vehicle, wherein the DC/ AC slow charger outputs less charge than the DC/DC fast charger to the electric vehicle.

6. The method of claim 5, wherein a first electric vehicle is charged by the DC/ AC slow charger and a second electric vehicle is charged by the DC/DC fast charger simultaneously.

7. The method of claim 5, wherein the DC/DC fast charger further includes an internet connected charger controller, the internet connected charger controller comprising a resonant converter module.

8. The method of claim 7, wherein the resonant converter module converts an input voltage from one or more of the grid and the renewable energy collection system into a DC output equal to an electric vehicle battery voltage.

9. The method of claim 1, wherein the renewable energy collection grid transfers energy to the battery system in the electric vehicle charging station, the battery system transferring energy to one or more of the electric vehicle and the grid.

10. An electric vehicle charging system, comprising:

an interface connectable to a land-based power grid;

a solar collector;

an AC/DC converter to convert grid current to a DC current;

a DC/DC charge controller coupled to the solar collector to feed current from the solar collector to a battery system;

the battery system coupled to the DC/DC charge controller to receive the first DC current and coupled to the AC/DC converter to receive the second DC current from the grid; and

an electric vehicle (EV) DC/DC interface coupled to the battery system to provide DC fast charging to the vehicle.

11. The system of claim 10, wherein the interface connectable to the grid includes a 3- wire single-phase 120/240 VAC hook-up.

12. The system of claim 10, wherein the battery system includes a plurality of 3.6-V li- ion batteries arranged in a plurality of battery packs in series, the plurality of packs arranged in parallel with one another.

13. The system of claim 10, wherein the battery system includes a plurality of 3.6 -V li- ion batteries arranged in a plurality of battery packs in parallel, the plurality of packs arranged in series with one another.

14. The system of claim 10, further comprising a battery management system with memory and a processor, the memory including instructions to diagnose operation of the system and generate indications of degradation.

15. The system of claim 14, wherein the battery management system further includes code for operating the system in a plurality of modes via a plurality of states.

16. A method for managing a solar-powered battery system in an electric vehicle charging station, comprising:

receiving a request to recharge an electric vehicle connected to the electric vehicle charging station; and

providing DC fast charging current to the vehicle from a battery module, where the battery module is charged via one or more or each of DC current converted from AC grid current and DC current generated from solar cells.

17. The method of claim 16, further comprising recharging the battery system via DC current generated from a solar canopy.

18. The method of claim 16, wherein the system is operated in a plurality of distinct and mutually exclusive states including an idle state, a discharge state, a recover state, and a top- off state, the method including not operating the system in a pre-defined and stored unavailable state.

19. The method of claim 16, further comprising balancing voltages of batteries in the battery module via current generated from a solar panel during a first balancing condition, and from grid current during a second balancing condition, the balancing conditions being mutually exclusive and selected based on operating conditions including one or more of a time of day, a cost of grid current, and a sun-load.

20. The method of claim 16, wherein the vehicle is a first vehicle, the first vehicle receives the DC fast charging current and a second vehicle receives a slow charging current simultaneously.