Mobility of tomorrow will include a gamut of futuristic solutions and technologies. A lot of these would be in the realm of alternate propulsions systems. For now, the one that is most promising is electrified mobility, which is set to witness large-scale adoption globally. While battery cost and their range continue to be high on everyone’s priority, charging mechanism, standards and infrastructure is no less important. We take stock on developments in the fast charging area.
Hybrid Electric Vehicles (HEVs) are only the stepping stone to the world of electromobility, and are known to offer limited features, in terms of clean mobility of vehicles. Battery Electric Vehicles (BEV) and Plug-in Hybrid Electric Vehicles (PHEV) are the real deal as far as zero-emission vehicles are concerned. While the charging requirements of HEVs are met by the internal combustion engine powering the vehicle during travel, BEVs and PHEVs require external power for charging the batteries that power the electric motors.
A robust charging infrastructure network thus becomes absolutely necessary to ensure faster adoption of electrified vehicles. Even with ever-increasing range of BEVs, and the backup offered in the form of an additional powertrain for PHEVs, range anxiety remains a concern that deters a large number of potential customers from EVs.
OEMs and solution providers around the EV space have identified this major hurdle of charging infrastructure globally, and have been working towards increasing the network of charging points as well as the various technologies around charging itself. In many markets, industries work with local governments to enable wider installation of charging infrastructure, increasing adoption rates for EVs as well as improving the environmental condition of the cities. With this being the first cog in the wheel of charging infrastructure to be addressed, the next step is to reduce charging time of these vehicles. Just as in the case of mobile devices, where majority are offered with quick or fast-chargers to help provide maximum charge to the battery in the lowest possible time, there has been a development of such technologies for EVs as well.
FAST CHARGING, EFFECTS
The quick charging of a battery is not as simple as just increasing the input power, since this would lead to quick deterioration of the battery itself. The fast charging period generally kicks in when the battery has enough power to support this higher load of current, and cuts off after a set period of recharge that is usually below full-charge. EVs are generally supported by two charging methods – alternating current (AC) on-board charger for both slow and fast charging, and direct current (DC) off-board charger, specifically for fast charging.
DC fast chargers produce more than AC units, and also cost more due to this capability. This is the reason why DC fast chargers are usually offered for a service fee, and are installed by operators who offer charging solutions to EVs. The usual charging ports offered by EV companies to end-customers are the AC kind, which can be powered by household sockets. They channel the power to the vehicle’s on-board charger, which then powers the EV’s battery. EV manufacturers are currently carrying out development work to offer on-board chargers that will allow AC fast charging. However, DC fast chargers do not utilise the on-board charger present in an EV.
The time it takes to charge a battery depends on factors like battery size, the maximum charge rate acceptable by the EV and the level of power present in the battery while charging. Lithium-ion (Li-on) batteries typically have the ability to accept power more rapidly when at a low state of charge as compared to the contrary. This means that a fast charger would work better on an EV with a Li-ion battery that has been discharged to a low power level. An important requirement to ensure that charging takes place at low levels is the connectivity of the entire charging infrastructure, which will then make it possible for customers to identify charging points and plan their travel route accordingly.
It must be noted that fast charging comes with its own set of after-effects, the main one being increased battery temperature, which results in reduced battery life and lower power retention, over time. This makes it highly critical for appropriate thermal management of batteries in mitigating dangerous thermal conditions on long distance tours with multiple fast charge events. In addition, such chargers offer solutions to constantly monitor the battery temperature and regulate power flow in order to avoid overheating of batteries.
While fast charging is gaining popularity all over the world, solutions are also being developed for quick recharging of batteries. One of these technologies is that of automated inductive charging, where power is transferred wirelessly from a ground-based charging pad to a receiver pad on the underside of the vehicle. For this type of wireless charging, all that a vehicle needs to do is be parked over the designated charging pad.
While this technology may not offer high-speed charging, such technologies could be installed at traffic junctions of designated EV lanes, where the vehicle can begin charging while sitting idle at a signal. This is besides the obvious installation of such systems in parking lots designated for EVs. Technology company Continental has already showcased its inductive wireless charging technology at a number of events.
Another charging solution that is also being adopted is that of battery swapping. This form of charging is not really charging at all, but rather the swapping of a battery depleted of power with one that is fully charged. While this form of charging may be relatively easy with smaller EVs like two and three-wheelers, it offers challenges in the case of passenger vehicles and buses. There is a requirement for a separate infrastructure to charge swapped batteries as well as aid in the extraction and insertion of batteries themselves. There is also the criterion of safety, which is said to be somewhat of an issue when it comes to removing a battery and replacing it with another, that too at such regular intervals. However, this technology would find its place in the shared mobility services segment of the EV space.
It must be noted that the quick charging technologies are growing, with new developments being carried out to make these systems safer and more reliable. A large number of global companies are also coming together to collaborate and develop common standards for inter-usability of charging infrastructure, on the road to higher adoption of electromobility. We have been seeing positive traction with regards to charging infrastructure from the Indian market as well, which leads one to believe that the EV ecosystem is taking shape in a rather positive manner.
TEXT: Naveen Arul