The Li-ion batteries should be capable of some very high discharge rates, but it's not unlimited. Depending on construction, anywhere from 2C - 30C discharge rate can be expected.

For a 14-18kWh battery, 10C would allow 140kW - 180kW discharges depending on SoC. But is it really that cut and dry?

If you've ever requested the maximum 120kW to the motor inverter, you'll know there is a certain SoC where it will NOT deliver that power. This means that there is a certain point in the standard Li-ion range of 3V - 4.2V, or 288V - 403.2V in a 96S pack, that peak power will be less than 120kW for one reason or another.

Just like the compressor on a belt and pulley system loads the engine in an ICE, a compressor at a full-tilt of, say, 4kW would load down the Li-ion batteries and you'd see a non-negligible drop in battery voltage. For a Spark EV with 15kWh of capacity, 4kW constitutes a 0.267C discharge. This would be added on top of the 120kW discharge, or 8C discharge + 0.267C.

I don't have LG's pouch discharge curve characteristics, but for cylindrical cells, there are many examples.

Take a look at the discharge characteristics for this 5Ah 21700 lithium cell:

https://lygte-info.dk/review/batteries2 ... %20UK.html
In these discharge curves, we see that throughout various discharge rates, the cell voltage on the Y-axis gradually diminishes. We also see that as we move down to lower discharge curves (amps listed in the legend at bottom of chart), the voltage is sagging more and more for higher discharge rates. Finally, if we compare where the curves end for various discharge rates, we see that we're able to utilize less total energy from the cell shown in the X-axis' cumulative Ah and Wh, suggesting a drop in efficiency due to a number of reasons.

0.267C (1/4C) would represent a 1.3A discharge curve (closest to blue line) on this graph. Compared to a gentle 1/20C or 1/25C discharge (top red line), we are seeing a voltage sag of 0.02V. It's not much, but this sag would be multiplied by 96 for 96 cells connected serially (the same current is flowing through all serial cell groups.)

Now let's slam on a 6C discharge (yellow line above). We see a 0.7V difference between the gentle discharge and the aggressive one. In a 96C pack, this 0.7V * 96 would turn into a 67V drop in cell voltage. But 6C for a 15 kWh degraded Spark battery pack roughly accounts for 90kW of power. It would need an 8C discharge rate for 120kW. To make matters worse, this power pushing through the internal resistance of the cells increases temperature as seen in the below chart with temperature in the Y-axis on right-hand side, requiring more power usage to run thermal management.

In other words, depending on the discharge characteristics of pouch cells, a full-power acceleration with the AC on could pull upwards of 9-10C on the batteries.

In summary, when we view some discharge characteristic data, we see that high discharge rates reduce available power from a system. As other high and low voltage loads are added to an already aggressive discharge, the voltage sag will eventually reach a point where peak power to the motor will be limited to protect the cells from overcurrent discharge, or a loaded undervoltage cutoff. Or it could be that the working voltage simply results in a lower available power (power = voltage*current). These limits will occur sooner if the state of charge is already below nominal. But at what SoC I haven't paid close enough attention.

Maybe someone can can stomp on the throttle and see at how many battery bars they aren't getting 120kW, just so we all know, hah.