They even have a comparison picture (the one above) of the two different Volt batteries, the Spark EV's battery, and the Bolt's.Integration of these batteries have drastically improved from model to model and it’s interesting to see the batteries go from a centrally mounted ‘T’ shaped system to a flat one that also contributes to the torsional rigidity of the car. These flat landscape cells in the Bolt are bundled into 96 groups of three with 288 cells in each battery and they are all connected in a parallel formation. Right under the seat is where those cells are double stacked to make use of every little bit of space available.On top of that, GM and LG Chem managed to increase the battery capacity to contain triple the amount of electricity the Spark could hold and with only twice the mass. The Bolt EV battery’s weight is 436 kg while the Spark EV’s is 215 kg.The main battery located under the floor is used strictly for propulsion and the accessories like radio, infotainment system, etc, is powered by a smaller 12-volt, lead-acid battery. Unfortunately, I don’t know where on the powertrain this smaller battery is located so if you know, feel free to point it out.The cells are already as tightly packed as possible and they even had to shift around a few components like charging modules and power distribution to get it this far. Anything more will have to come from improvements to the battery cell capacity. Here’s a front, rear and side diagram of the battery and it’s pretty tight in there.