43% more energy with same EV battery size achieved in Chinese Firefly model

Nio has unveiled its new longer range 60kWh battery variant of its popular Firefly electrical vehicle (EV). This new battery provides the EV with an increased Chinese testing cycle (CLTC) rated range of 348 miles (560 km), up from 261 miles (420 km).

All this within a battery pack of the same dimensions, reportedly without increasing the vehicle’s overall weight. This is significant as it appears to offer better performance from a limited space (the battery) without adding weight.

The Firefly had an original battery capacity of 42 kWh, meaning the new battery is somewhere close to a 43 percent increase. This is stored energy capacity and doesn’t necessarily translate 100 percent into driving range.

In fact, according to reports, the increase in range is somewhere close to around 33%. This is for a variety of reasons, but part of it is due to the battery management system reserving capacity to protect new cells.

New battery: same size, more range

So, how was this achieved?

Designed by Contemporary Amperex Technology Co., Limited (CATL), the new battery uses something called ternary lithium cells. These cells have an energy density of 187.2 Wh/kg, achieving a high volumetric efficiency of 73.4 percent.

While not entirely clear, the second stat here likely relates to how efficiently the cells are packaged inside the pack, rather than its actual volumetric energy density efficiency.

If so, this would mean that the cells themselves occupy only some of the available space. The rest comprises things like structural supports, cooling systems, electrical connections, etc.

So, CATL has managed to increase capacity by combining higher-energy-density cells with more efficient packaging. In other words, you can get more electricity into the same physical box without making that box heavier.

Another important change is the battery chemistry. The original 42 kWh battery used lithium iron phosphate (LFP), whereas the new battery has changed to nickel-cobalt-manganese (NCM).

Nice to have options

The latter benefits from higher energy density but at a cost. Materials are generally more expensive, and cycle life can suffer when compared to LFP. That said, NCM tends to perform better in colder weather.

NCM cells are generally more susceptible to thermal runaway, so additional protection is necessary. But Nio says its new pack includes enhanced thermal protection and several technologies intended to reduce long-term degradation.

Trade-offs like this aside, the new battery can reportedly be installed in an older Firefly without replacing the vehicle. This kind of modularity allows existing owners to upgrade vehicles and could potentially accommodate further upgrades as battery technology improves..

According to reports, Nio is offering both purchasing and rental options for the new battery-carrying Firefly. Customers can purchase it for $20,400 (about 136,800 Yuan), which compares to between $17,900 (119,800 Yuan) and $18,800 (125,800 Yuan) for the older variant.

Alternatively, customers can rent the new 60 kWh battery for around $90 (599 Yuan) a month through its “battery-as-a-service” (Baas). For customers wishing to upgrade older Fireflys, costs come in at around $2,500 (17,000 Yuan) for full purchase or a $450 (3,000 Yuan) service fee for BaaS customers.