The cost and complexity of setting up a large fast charger is immense but not a technical limitation. The only physical barrier to charge faster is the Battery accepting high power. Transport of ions at a rate faster than allowable forms dead spots and plating on a cellular level which leads to long term reduction in battery life. Moreover, as more power is pumped into the Battery, more heat is generated which in turn lowers the energy capacity of each Cell in the Battery. This then leads to Battery overheating which then results in slower charge times and greater capacity fade over time. 

This all is the primary reason only some Production Vehicles such as the Tesla Model S, Hyundai Ioniq 5 & Rivian R1T with Highly Engineered and Optimized Batteries can charge within 20 minutes consistently over time. The Cell Selection combined with their Voltage and Thermal Management Systems are at the core of what enables their superior charge performance. To truly enable mass adoption though, a similar but more scalable and affordable approach using standard easily available Li-ion chemistries is imperative. 

Most vehicles on road today use one of two Li-Ion chemistries:

  1. Lithium Nickel Cobalt (NC x)  where x can be manganese cobalt oxides or aluminum oxides 
  2. LFP (Lithium-Ferrous-Phosphate)

NCM and NCA are the most energy dense chemistries in mass production. Battery Packs that are required to be Small and Portable (Gogoro, Ather) or Extremely Large and Energy Dense (Rivian, Porsche) primarily use similar chemistries. Today, these Battery Packs are pushing the envelope of energy density and therefore are able to achieve the maximum vehicle range possible. LFP on the other hand, is ~10% Safer and Cheaper to implement and has started to replace NMC in Buses, Trucks and Low Cost Cars that can accommodate the 30% increase in weight, size and volume. The lack of rare metals such as Cobalt and Nickel in these cells also allow faster scale for Cell Manufacturers without the reliance on mining countries.

The current production threshold for Fast Charge for 4 Wheelers is at ~20 kms/min (Tesla, Rivian) and 1 km/ min (Ather, Ola) for 2 and 3 Wheelers. All 4 companies can do similar rates using an NMC or LFP cell with ~10% better life for the LFP Cell. Certain modified Li-ion chemistries such as LTO can do >5 kms/min for 2, 3 Wheelers but at a 50% premium in price. The future of faster charging is going to be determined by cell chemistry changes and battery engineering improvements. 

The Charge and Battery Details for various vehicles is as shown below:

#

VEHICLE NAME

BAT SIZE kWh

CELL

CHEM.

CHARGER INPUT

CHARGE TIME in mins

CHARGE RATE 

Kms / min

1

Tesla Model 3

50

NCA/LFP

CCS2

20

20

2

Rivian R1T

180

NMC

CCS2

30

19

3

Tata Nexon

30

LFP

CCS2

60

6.5

4

Euler HiLoad

12

NMC

DC01

45

2.8

5

Mahindra Treo

7

LFP

AC

600

0.1

6

TVS iQube

2.5

NMC

AC

220

0.4

7

Ather 450

2.5

NMC

AC

90

0.9


 

Future of Fast Charge

To attain faster charge rates greater than 20 kms/min, there will be few key approaches:

  1. Use a Cell Chemistry that allows easier movement of ions and in turn has higher efficiency. Most work in this world is still under research and the solutions that are commercialized are far too expensive or inefficient to implement at mass scale. The main alternatives that are being worked upon to solve this problem are:
    1. Solid State Batteries (Prologium, Quantumscape)
    2. Silicon Anodes with added Nano materials (Storedot, Amprius)
    3. Modified Li-Ion Chemistry (Molicel, Toshiba)

Change in Internal Structure of Cell to enable Better Performance

 

  1. Using an Advanced Battery Pack Design that allows extremely high power to charge cells will be the approach most companies who can fast charge today use (Hyundai, Mercedes, Rivian, Tesla). These systems have highly optimized thermal and voltage management systems that are able to utilize the cells to their fullest capacity. Improvements in chemistry beyond NMC and LFP will only allow these solutions to charge faster. The choice of materials, internal packaging and precise thermal transfer methods lead to superior charge speeds and consistent performance over time. 

Section of Mercedes EQS Battery shown

 

Modern 4 Wheeler Batteries in the Mercedes EQS or Tesla Model S used advanced direct contact methods to allow ultimate performance and safety. Most batteries in India today use no cooling or management at all. Cells are placed in a Plastic or Metal container with very poor contact, dissipation or safety consideration. Going ahead, the inclusion of Thermal Retardant materials that can maintain temperatures under 60 deg C even in 50 Deg C ambient will be the true enabler to Safer, more reliable batteries. 

  1. Battery Swapping is also being used to solve the problem of slow and inefficient charging by allowing vehicles with removable batteries to swap a depleted battery with a battery from a rack of 4-8 similar fully charged batteries. The system has been implemented at scale by Gogoro in Taiwan and a similar standardized swap platform is being implemented by the Indian Govt. by the end of 2022. The Standard will mandate the use of a certain battery size and communication protocol which will allow interoperability of batteries amongst 2 & 3 Wheeler Vehicles by different OEMs. Battery manufacturers have to engineer batteries to be >1.2 kWh, <12 kg and 310x180x160 mm in size and as long as the externals and connector are the same, the internals of the battery are up to the manufacturer. This enables the opportunity for swap stations to interchange batteries and battery manufacturers to implement superior technology to enable better performance, safety and life. One of the big enablers for swap will be a high utilization rate of the batteries. The longer the batteries sit idle charging, the longer it takes consumers to swap. The unit economics make sense when batteries can charge within 1 hour without compromising life or safety. Currently Bounce and Yulu take over 3 hours to charge each battery whereas Sun Mobility charges within 1.5 hours using an Air Conditioned Swap Station. A Safe, Reliable, Robust Battery operating on a Standardized Platform capable of Fast Charge will be the key to allowing Battery Swap to exist. 

 

                    

   Bounce And Gogoro Swap Stations