Slow charging, fast charging and battery swapping – potential areas of improvement for the industry

In this opinion piece, Rahul Bollini shares his perspective on the opportunities and challenges with the three models of battery recharging available to EV owners. He highlights a few prevalent practices industry can improve upon and recommendations for the overall EV charging ecosystem.

The three battery charging models available to EV owners are:


– Slow charging at home/workplace (2W, 3W, 4W)

– Fast charging at a commercial charging station (2W, 4W)

– Swapping at a Battery swapping station (2W, 3W)

Slow charging at home or workplace

Slow charging is the most preferred and most independent source of charging the EV battery. It provides the maximum battery life (cycle life) and is safer than fast charging, especially for NMC batteries. It is also the cheapest way of charging the EV battery since the EV owner only has to pay for the energy. Its use must be popularized at workplaces in order to enable faster adoption of electric 2Ws and 4Ws for the personal use segment. Electric 2W owners can carry the chargers along and use the charging points at the workplace. This option also avoids any kind of confusion caused due to variations in charging connectors in the electric 2W space.

Slow chargers take between 4 and 5 hours to charge a 2W or 3W battery fully. EV manufacturers claim that slow charging is good for the life of the battery. But what’s the point in charging the Lithium-ion batteries at the speed of traction lead-acid batteries?

Slow charging’ can be faster if EV manufacturers provided a higher ampere rated charger along with the EV. By using a double the ampere rating charger, the charging time would halve. 

2W OEMs typically provide a 6A charger which costs around INR 2,300. A 15A charger costs around INR 4,000. The same goes for electric 3Ws where OEMs typically provide a 15 A charger that costs about INR 4,000. They could provide 30A which would cost around INR 7,000. By raising the absolute price of the vehicle by a small amount, the overall experience of EV ownership can be drastically improved in terms of time taken to charge the vehicle at home or office.

Fast charging at commercial charging station

A fast-charging station is the way to recharge when in need of a quick charging solution. I believe that charging up to 50% of the battery in 30 minutes is safe. Charging any faster than this rate would need additional provisions of thermal management in battery packs. Good quality Lithium-ion cells (grade A cells) allow for fast charging rates without much degradation and can last for a decent time in Indian operating temperatures. However, grade A cells can be expensive, and hence it is not preferred by all Indian battery pack manufacturers. Grade B cells are popular because they are cheaper, but they have lower performance noticeable in the long run, and they compromise on the safety aspect.

Grade A cells have the electrochemical property to charge faster and handle heat better and last longer. Having worked both in India and internationally in the Lithium-ion cell chemistry space for more than 6 years, my personal recommendation of NMC cell is the LG 3000mAh series in 18650 cylindrical form factor. They have the best IR in the industry, allow for fast charging and have a good cycle life in the Indian operating temperatures.

Battery swapping station

A battery swapping station (BSS) is where battery packs are housed and charged fully to be replaced with discharged battery packs from EVs. An EV owner can visit a battery swapping station and replace their low State of Charge battery pack for a fully charged battery pack for a fee.

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Representative image | Source – Sun Mobility

This fee covers the cost of the BSS infrastructure, the cost of employees (maintenance staff or staff in lower automated stations), the cost of recharging the battery, the leasing cost of the battery and the degradation factor of the battery per use. In the case of a third party BSS, profit expectations also have to be added to the swapping costs.

Swapping requires standardisation

Swapping operations require standardization in the battery voltage and dimensions. Standardization in the EV battery voltage is happening at a good pace. BSS can be a good model for companies with a large EV fleet – they can run a BSS for their captive consumption to save time in charging their EVs.

BSS owned by third parties can be challenging since various EV manufacturers have different dimensions of the battery packs. An ideal case scenario for BSS owned by third party companies would be that the EV owners buy EVs without batteries and completely depend on the BSS companies for their battery needs. This way the total ownership and control of the batteries shifts to the BSS company. Unfortunately, this is not a popular model in India since buying an EV without a battery would make an EV owner ineligible for the FAME 2 subsidy and the subsequent subsidies offered by some of the Indian states. Some further policy clarifications (with respect to incentives) are awaited for the model where EVs can be sold without the batteries.

One way to be able to claim subsidy and the need for standardization of battery dimensions for the BSS model is to have a provision for dual batteries in an EV. The EV must have a primary battery, which is provided by the manufacturer and remains fixed in the vehicle and a secondary battery, which can be picked up from a BSS as and when necessary. The secondary battery will be completely owned by the BSS company. But for this model to work out, the EV manufacturer must provide a standardized additional space to accommodate the additional battery. The dual battery model will also provide the potential to double the range of the EV, hence completely ending the range anxiety among EV buyers.

This article was first published in EVreporter September 2021 magazine.

Rahul Bollini has over 6 years of experience as an international Lithium-ion cells R&D consultant and has closely worked with Indian, American, European and Japanese companies with hands-on experience in Lithium-ion cell engineering and complete fabrication process. He has studied Energy Business and Finance from Pennsylvania State University, USA. Rahul can be reached at bollinienergy@gmail.com.

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One thought on “Slow charging, fast charging and battery swapping – potential areas of improvement for the industry

  • Nice information..! Above are the genuine challenges for EV automakers. Too much scope for improvements. You can get swappable batteries in electric scooters by AMO Electric Bikes.

    Reply

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