EV Charging 105: Battery Swapping

Swapping or charging

Battery swapping is often hyped as the 'silver bullet' to solve the challenges associated with the charging of Electric Vehicles. If you have been reading my articles on EV charging, you know by now, that charging of batteries is a time-consuming process. At the heart of every EV is a battery, and quite often the charging of the batteries happens by connecting the vehicle to a plug point. If the batteries are to be charged inside the EV as mentioned before, then the vehicle needs to be parked for the entire duration it takes to charge the battery. Long charging time is a hassle for the vehicle owner who is used to quick refuelling at the petrol pumps. Many a time, the time lost for charging is also loss of income for the EV user.

An interconnected and perhaps the biggest problem with EV charging is about the need for parking space for charging. And as we know, land is expensive and the parking space requirement has a huge impact on the viability of any EV charging business. From the perspective of EV charging business owner, least space requirement is the best-case scenario. One can always look into options like providing charging facilities at existing parking spaces to solve the land problem. Even then, if the time of refuelling is be reduced the same space can serve more EV consumers.

But on the other hand, as charging is a chemical reaction that produces a lot of heat, thermal management of batteries during charging is very important. In fact, how fast you can charge pretty much depends on thermal management of battery, and the battery chemistry itself. It is also interesting to note that every time an electric car is to be charged its airconditioning system needs to switch on. The discussion on thermal management is especially important for a tropical climatic zone like India, with hot summers.

One thing that complicates the thermal management problem for India is that our vehicular mix is dominated by two-wheelers and three-wheelers which naturally does not have any cooling systems. Incidentally, there is a lot of push for electrification of two-wheelers and three-wheelers as it is an environment-friendly and economical option. However, the charging of these batteries is a different ballgame. We will deal with two and three-wheeler charging in detail in a separate article.

An effective way to solve the problem of long charging time, thermal management and parking space requirement is to separate the battery charging process and vehicle refuelling process. All you need to do at a refuelling station is to swap the discharged battery with a fully charged battery. You can recharge the discharged battery at the refuelling station itself or elsewhere. Once this battery is fully charged, the same can be used to swap another discharged battery. One example you would have read in news recently about battery swapping facilities set up for electric auto-rickshaws at petrol pumps in Kochi and Lucknow. Ola has also set up a swapping facility for their electric rickshaws in Gurugram. In the image below you can see racks of battery charging panels for a swapping facility.

( Battery chargers at a battery swapping facility. Picture courtesy: Quartz India)

Evidently, the space needed to set up a swapping facility is much much smaller than a charging facility. Battery swapping and charging are two distinct activities now, so you need to plan two operations: How to charge the battery and How to undertake the swapping. All together the swapping appears as very simple all together, but the history of Better Place showed that planning of battery swapping operation is not a piece of cake.

(Battery swapping station set up by Better place)

Better Place and battery swapping

It is impossible to write about battery swapping and not talk about Better Place. Battery Swapping as we see in the EV ecosystem today started in Israel with Shai Agassi. The purpose of his company was to make the world 'a better place' by 2020 with inexpensive electric vehicles, and the pathway to that was retrofitting conventional cars into electric vehicles. Since batteries are expensive, to achieve cost reduction of an EV it needed to be sized as small as possible.

But the range of an EV is proportional to its battery capacity. Smaller battery capacity meant the smaller driving range for Better Place EVs. The end result of the exercise was that Better Place had to come up with another solution to support their small range electric cars. And the initial the battery swapping solution they arrived at was really costly. The company eventually went bankrupt due to multiple reasons, and needless to say, battery swapping got a bad name.

In conclusion, the lessons learned with respect to battery swapping from the Better place is that

1. Battery swapping is not a zero-sum game if the infrastructure needed for charging and swapping is not cost-effective
2. Not much is achieved if swapping is planned to reduce the upfront cost of EV by reducing the size of the battery.

Why swap then?

The next question in your minds is 'why swap then?'. I have already told you the answer to the why. Battery swapping offers the comfort of easy refuelling, with less real estate footage. It is a convenient solution for the user and the service provider. It also provides better control over the charging of the battery, which is the expensive element. It also provides access to monitor the health of the battery, after all, if the batteries degrade faster electrification will become an expensive affair. When electrifying vehicles without air conditioning like two and three-wheelers in hot climates, swapping makes a lot of sense. Having said all that, it is important to plan your swapping facility well.

How to swap the batteries?

The swapping operation involves the removal of a battery and replacement with another. Here the weight of the battery matters a lot. A 1 kWh Lithium-Ion battery weighs at least 10 kg. This is a weight that a person can easily lift by themselves. As 1 kWh can be considered as a typical size for a two-wheeler battery, its a one-person job. All the person needs to do is to lift the battery and insert it into a charging docket. And get a charged battery in exchange. This is precisely what happens at Gogoro's swapping stations which looks like 'cool vending machines'. The smart thing they did is to design the battery with a handle that can be lifted easily as you see in the image below.

( Gororo swap facility. Picture courtesy Electrek)

Swapping gets challenging as the weight of the batteries increases. However, it is still possible to manage it up to some weight that can be lifted with the help of another person. A few of the swap service providers like Lithion Power has chosen an assisted swapping facility if their batteries are heavier. In their swap facilities, there is an assistant who helps the EV customer in lifting the batteries. Two people can easily manage the battery removal and replacement process for electric rickshaw batteries.

A few other service providers like Sun mobility has opted to focus on designing handy lightweight smart battery packs which one person can lift easily. Sun mobility uses batteries of standard battery pack size regardless of vehicle type. The number of battery packs will be different for a two-wheeler and a three-wheeler though. For example, a two-wheeler might have only one battery pack whereas a three-wheeler might have two or three.

(Car battery swapping in China, Photo Courtesy: PlugIn India)

Swapping systems for electric buses and electric cars are much more complex and costly. As batteries get more heavy complex hydraulic lift systems are needed. These systems could be fully automatic or assisted. In China, car batteries are lifted using hydraulic lifting trolleys in human-assisted swapping facilities. Fully automatic swap facilities such as those demonstrated by Tesla are pretty impressive in their design, though they are costly affairs. Similarly, bus swapping facilities such as the one set up in Ahmedabad, India has swanky robotic systems to do the swap.

(Tesla model S battery swap, Video courtesy: Tesla)

How to chose between charge or swap?

Coming back to the original question of 'charge vs swap', it can be concluded that both has its merits and demerits. Charging is possible everywhere as electricity is practically everywhere. But it is impossible to bend the limitations of charging time due to thermal management and battery chemistry. On the other hand, swapping can solve time, land and thermal management problem associated with swapping.

An important thing to remember here is that efficient vehicle design calls for the least weight. It does not always make sense to design an EV with a heavy battery pack. Provided adequate charging/swapping infrastructure is available it is better to make lighter EVs with small batteries. This is extremely relevant for large vehicles like electric buses and goods carrying vehicles as less battery weight means more passenger/goods carrying capacity.

The choice of swap or charge finally depends on the cost associated with the swapping infrastructure as well. Innovative low-cost swap facility designs might be the short term approach to swapping, though fully automatic systems could be the long term norm.

Link to other articles in this series:

Link to Part 1: EV Charging 101

Link to Part 2: EV Charging 102

Link to Part 3: EV charging 103

Link to Part 4: EV Charging 104

Link to Part 6: EV charging 106?

Note: I am an electrical and electronics engineer and not an expert in EV or batteries. However, my current area of research is EV charging, and my auto-didactic tendencies are lately on overdrive with my focused reading. The article is a summary of my notes from multiple sources. A fellow EV enthusiast may find it useful, though caution is advised. As this article intended to help me in improving my writing skills, please do let me know how I am doing in the comments section.