Battery: Chevrolet Bolt EV vs Chevrolet Spark EV
Let’s take a look at these great batteries.
GM’s electric cars use LG Chem cells for their batteries. These cells are considered by GM’s competitor Renault-Nissan CEO, Carlos Ghosn as top notch. I understand why.
Let’s make a quick comparison between Chevrolet Bolt EV and Chevrolet Spark EV batteries.
The Chevrolet Bolt EV’s battery is made with 288 (96s3p) LG Chem cells, I think that each cell is rated at 65 Ah and 3,75 V. I’m not sure about the 65 Ah capacity, but this is what I was told a year ago by a LG Chem worker. This represents a total of 70,2 kWh (288 x 65 Ah x 3,75 V). The battery volume is 285 L and the mass is 435 kg, this means an energy density of 246 Wh/L and 161 Wh/kg at the battery level, not cell.
While the Chevrolet Spark EV battery is made with 192 (96s2p) LG Chem cells, each cell is rated at 27 Ah and 3,75 V. This represents a total of 19,44 kWh (192 x 27 Ah x 3,75 V). The battery volume is 135 L and the mass is 215 kg, this means an energy density of 144 Wh/L and 90 Wh/kg at the battery level, not cell.
Since GM is buying a lot of 65 Ah cells for the Bolt EV, why not using them also in the Spark EV battery and sell both electric cars worldwide?
The battery capacity would have a small increase, the 19,44 kWh would increase to 23,4 kWh (96 x 65 Ah x 3,75 V), and since the new cells have better volumetric and gravity energy density, instead of the current 192 cells, only 96 would be needed. This would mean a lighter and smaller new battery, it would increase the Spark EV efficiency and range. GM should sell the Bolt EV for range and the Spark EV for affordability. With the new cells GM should also replace the old Spark EV body with the new one that is already used in Spark’s newest gas version…
Back to comparing the batteries…
Both batteries have liquid active thermal control that is very important to keep the battery at ideal temperature, since high temperatures damage the cells.
We know that the Spark EV’s small 19,44 kWh battery can handle high charge and discharge rates, since it can provide 120 kW – 105 kW are intended to the motor – and can take up to 50 kW in CCS DC fast chargers. While Bolt’s 70,2 kWh battery can provide at least 150 kW to the electric motor and something more to the electronics.
What is still unknown is how fast the Bolt’s battery can be charged in a CCS fast charger. GM has been saying that this electric car with more than 200 miles EPA range will charge at 90 miles per 30 minutes. This means that a complete charge would take more than an hour in a CCS fast charger. But we have to take in mind that GM has to say this because virtually every CCS charger in the USA is limited to 50 kW and GM doesn’t want a class action lawsuit.
Since in Europe we already have a few 150 kW CCS fast chargers, Opel might reveal how fast the Ampera-e can actually charge. Anything less than 100 kW is a major letdown, 120 kW would be great.
Update: I did a mistake. The LG Chem worker never mentioned a 55 Ah cell, it was 65 Ah. The kind of cell that was probably chosen to be in Renault Zoe’s new 41 kWh battery as you can see here. So I revised the article accordingly.