In general, a larger battery pack can be charged faster. So a Tesla Model S with a large 100 kWh battery can be charged at higher power than a BMW i3 with a 21 kWh battery. This is also the main reason why the current crop of plug in hybrid electric vehicles (PHEVs) cannot fast charge: their battery packs are simply too small. Most PHEV manufacturers do not include the additional hardware (e.g. extra inlet and wiring) in the car.

When the battery is almost fully charged the charge speed drops to prevent the battery cells from overheating. Typically at 80–90% SoC the speed drops and charging will slow down further closer to 100% SoC. That is the reason why fast charging is most effective between 0% and 80–90% SoC. Also, as mentioned before, the latest batteries are even set up to maintain a charge level of between 10-90%.

Battery cells operate most effectively between 20–25 degrees Celcius (68–77 degrees Fahrenheit). When battery temperature is too low or too high, the BMS reduces the requested current to protect the health of the battery cells. If the battery pack is equipped with a heating or cooling system (e.g. the BMW i3) the BMS will activate this system in order to control the cell temperature. Note that battery temperature is not only influenced by the outside temperature, but also by (highway) driving and (fast) charging as this will generally increase battery temperature.

When designing a battery, manufacturers have to make choices on size, weight, costs, life and performance of a battery. Depending on the target audience of the vehicle they could compromise battery performance over costs and weight for instance. Alternatively, a higher end vehicle will have better performance and may include battery temperature regulation, but it will also come with a higher price tag.