Hybrid/ Electric Vehicle Charging

As more and more vehicle makers continue to invest in electric and hybrid vehicles, the need for quick, reliable and convenient charging continues to increase. One of the largest hurdles in the mass-adoption of EVs has been range anxiety, as such vehicles need long durations to recharge their batteries. Engineers across the world are trying to address this problem by making the batteries better and also improving the charging technology.

In the past decade, charging technology has grown manifold, laying the foundation for development of a charging infrastructure. Presently, there are three ways of charging an EV’s batteries – public/personal outlets, quick-charge stations and on-board charging. For all three systems, especially the first two, it’s imperative to maintain battery temperature as well.

PUBLIC/PERSONAL OUTLET

Such charging outlets can be installed in homes, offices and streets and offer 120 V or 240 V charging. A 120 V outlet is the most common across homes and has a 15 A circuit breaker. In simpler words, the maximum energy that can be transmitted from this outlet is 1,800 (120 x 15) watt per hour or 1.8 kWh. Hence, if a car needs 18 kWh of energy for full charge, it would take about ten hours to charge the batteries from such an outlet. These figures are indicative and could vary due to various factors.

Such chargers normally do not have a temperature monitoring system and mostly work on assumptions. Although using these outlets is very convenient, in most cases of advanced EVs, they might not be able to deliver a full-charge even through the whole night.

The next option is the 240 V outlet with 30 A, which delivers up to 7,200 watt per hour or 7.2 kWh. These types of outlets can charge most EVs in about five to eight hours and are best suited for overnight charging.

QUICK-CHARGE STATIONS

Quick-chargers were once touted as being capable of making EVs practical and adoption-friendly. Such chargers can recharge lithium-ion batteries to about 80 % in just about 30 minutes. This is possible due to the outlet capacity of about 480 V and 400 A. The power transfer translates to a kWh rating in excess of 190. Such chargers at times constantly monitor the battery temperature and adjust the power flow in order to avoid overheating of batteries, a common trait of lithium-ion. It must be noted though that the technology still has many challenges due to which it hasn’t been adopted widely.

One key issue is convenience as such high-capacity charging points aren’t available in residential or office areas commonly. Installing them can be quite expensive, thereby offsetting the cost advantage offered by an EV over a similar petrol or diesel vehicle.

Another challenge is that the rapid flow of current despite all management systems causes the batteries to heat at times. Over a period of time, such regular exposure can reduce the battery life. The high replacement cost of batteries in a short duration would again send the economics of any EV for a toss in the long run.

However, as you read this article quick charging is getting safer and reliable by the day. Multiple OEMs across the world are talking about a recharging infrastructure primarily made up of quick-chargers. Going by the pace of development in battery related electronics and battery management systems, we can expect quick-charging to become popular in the next three to five years.

ON-BOARD CHARGING

When a conventional vehicle decelerates or brakes, a large amount of kinetic energy is converted into heat and wasted. In an EV or a hybrid though this energy is recuperated and used to add to the overall driving range. During braking, the electric motor switches to generator mode. The wheels transfer the kinetic energy through the drivetrain to the generator, which in turn converts this energy into electricity. This electricity is stored in the vehicle’s main battery and is mostly used for acceleration purposes.

Since the generator here provides friction braking to the wheels, the wear and tear of brake pads is considerably reduced. This also leads to lower carbon emissions and brake dust pollutants.

OUTLOOK

Charging and its efficiency and practicality will play an important part in the success of electromobility. Any breakthrough advances here along with that in battery efficiency can lead to an earlier adoption of these vehicles. As time progresses, it’ll become important that we look at more than just the charging technology. What will ultimately make charging a strong link in the electromobility chain is its transformation into widespread infrastructure.

Author: Auto Tech Review