What are the Hardware and Software Challenges in EV Battery Charging System?
Electric Vehicles’ sale has been seeing an upward trend in countries like United States and China. In USA alone, 1.2 million electric vehicles are on the road. Compared to 2017, the sale of EVs has gone up by 81% in 2018.
But if you compared this number with internal combustion (IC) engine cars sold in the same year, the figure seems dismal. So, what’s stopping EVs from mass adoption? Well that’s almost a no-brainer! The inadequacy of the charging stations and that too, fast charging stations, is one of the culprits.
Can’t we have a higher number of EV charging stations just like we have gas stations?
It’s easier said than done, as the efforts required to set up a petrol/diesel station is nothing compared to a public EV charging station. There are issues related to protocols, safety, software/hardware challenges, and what not.
In our latest EV blog, we focus on the challenges related to the development and setting up of a battery charging station for electric vehicles.
Here, it is also very important to understand that battery charging stations are just one side of the coin. Protocol incompatibility issues along with safety challenges are also associated with the battery charger fitted inside the electric vehicle.
Before, we start enumerating the challenges and the possible solutions, let’s first understand how a typical EV battery charging system works.
How Does an EV Battery Charging System Work?
A battery pack and an on-board battery charger system replace an IC engine in an electric vehicle. The on-board battery charger system connects to an AC supply network (mains), converts power from AC to DC and charges the battery pack.
Alternatively, an off-board charging station can directly deliver DC and charge the batteries at a faster rate.
The fixed cable from the charging station has a charging connector based on the protocol supported by the station. If the charging station supports multiple protocols, it might have multiple connectors.
- Once the connector goes inside the charging inlet (vehicle), there are a couple of conditions that have to be met. The charging type (AC or DC) is chosen and, in some protocols, the mode of charging is also selected.
- After the software and hardware checks are complete, the charging begins. The software inside the on-board battery charger or the firmware installed in the external charging station monitors the charging. In an instance of overvoltage or overcurrent, the charging systems take appropriate measures.
In a basic EV charging setup, the aforementioned actions are involved. However, depending on the protocols, additional safety and authorization mechanism can be put in place.
The battery charging system might appear fairly simple, but there are tons of challenges associated with the development and setting up of such a system. Let’s learn about them in detail.
Hardware and Software Challenges in an EV Battery Charging System
Challenge 1: Conformance to Various Charging Protocols: Software & Hardware Challenges
Can you charge a smartphone with a micro USB port using a Type-C charger? No, you cannot, as the charging point slot is completely different.
Now try charging a smartphone that does not support fast charging, with a fast charger. It won’t work either. And even if it does, the charging will be at a regular or slow speed.
How does this example tally with the charging process in an electric vehicle?
- There are several types of AC and DC chargers for EVs with different communication protocols. An incompatibility between the Electric Vehicle Supply Equipment (EVSE) and the AC-DC converter on board the vehicle could result in charging issues.
- There could also be Voltage/Current/Frequency mismatches or other such incompatibilities that prevent the intended charging.
As far as electric vehicle charging systems are concerned, the stakes are high, and protocols are more complicated. Various protocols such as CHAdeMO, CCS (Combined Charging System) and Bharat EV Specifications are in use and a battery charging station has to be designed to incorporate the relevant protocols.
This is important because the battery charger system inside an EV may be equipped with any of these protocols and the charging station has to be prepared to cater to the protocol.
As these protocols have different voltages/currents, handshake methodologies and safety mechanisms, the cost to incorporate them is quite high. This, in turn, increases the cost of the charging station.
- Hardware Related Challenges: The signal lines facilitate communication between the charging station and the electric vehicle. Hardware Components like proximity sensors and control pilot manage the connection and ensure that the charging starts when the conditions stipulated in the protocol are met. The challenge lies in designing the hardware for various protocols with different conditions.Some of the other issues that need to be fixed to meet the conditions of these protocols are power issues, heat dissipation, insulation, grounding, voltage measurement, etc. The hardware is not alone in these endeavors as the software components also take up various roles.
- Software Related Challenges: Charging protocols mandate that the charging should start only when certain criteria like connection to ground, current filtering, etc. are met. The software needs to be designed to detect that such criteria have been fulfilled.The real challenge here is to program the software to detect the protocol that the EV supports and change the charging modes accordingly. For instance, the CCS (Combined Charging System) supports SAE J1850 for diagnostics and data sharing applications in EVs. Hence, the battery charger system has to be equipped with the same protocol.
Challenge 2: Safety during Voltage Fluctuations
Risks like Voltage Fluctuation, Ground Fault and Over-Current pose potential threats for both the battery charging station as well as the electric vehicle being charged. A sudden spike in voltage may end up damaging some very expensive components.
Regulating the voltage is a challenge in itself, as various scenarios are possible where different actions are required to be taken. For instance, CCS protocol mandates that the battery will charge only when the voltage is in the range of 170-230 volts. If the voltage drops below 170 V, there has to be some converter or stabilizer circuit to increase the voltage, and vice-versa.
However, if the voltage is in a range that is beyond regulation, there should be a provision to shut down the battery charging station.
Here, the software components play a pivotal role of monitoring the voltage and signaling the hardware circuits to regulate the voltage accordingly.
Noise filtering is another aspect that requires software and hardware components.
In the context of the battery charger inside the vehicle, functional safety also comes into the picture. The voltage fluctuation while charging an EV can be an ASIL-D level risk. In order to mitigate this risk, the high voltage component inside the vehicle needs to be developed as per ISO 26262 standard.
EMC/EMI tests as per IEC 61851 standard are additional safety assessments that need to be performed.
All of these safety activities may turn out to be quite expensive; hence, these pose a major challenge in the mass-adoption of EVs.
Challenges 3: Achieving Fast Charging Capabilities
One of the biggest advantages that an Internal Combustion Vehicle (ICV) has over its EV counterpart is the time taken for “refuelling”. In electric vehicles, DC charging is an exciting breakthrough as it charges at a much faster rate. But it has its own set of challenges.
DC charging occurs at 200-300 kW which is almost 5 times the rate of AC charging. Higher power entails higher risk related to electric shock, overvoltage or overcurrent. The cost obviously become higher, thus impacting the entire ecosystem.
Several protocols like CHAdeMO and CCS have come up with unique specifications that aim to make the process less costly, universally applicable and reliable.
The Bigger Picture
Stakeholders in the electric vehicle industry are coming forward to standardize battery charging systems. The path to standardization encompasses the discovery of solutions to overcome the challenges listed here.
Establishment of protocols like CHAdeMO and CCS are testament to the conviction of the EV industry to make EVs the mainstream vehicles (and possibly replace IC engine cars completely) over the course of the next few years. Let’s keep our fingers crossed!