Another aspect related to battery temperature is how quickly the battery can reach problematic temperatures. A BEV battery has a thermal
time constant which determines how fast the battery will reach the ambient temperature, and likewise how fast the battery will cool once it's heated,
given a lower ambient - the heat soak effect.
Another battery heating process results from the battery's internal heating, the battery's losses (I^2 x R, I-motor current,R-battery resistance).
This heating process can occur more rapidly based on the motor current (vehicle speed) than a changing ambient temperature. The battery has
a thermal resistance to a vehicle's body, and the body has a thermal resistance to ambient. Typically the thermal resistance is much lower from
the battery to the body than the body's thermal resistance to ambient. The net effect is that the battery can heat up more quickly from its
internal losses than from a change in ambient, given high motor loads, e.g. vehicle speed. That's why without TMS, the Leaf's battery temperature
needs to be monitored while driving besides just being concerned about the effect of an ambient temperature on battery temperature,
which affects battery degradation.
time constant which determines how fast the battery will reach the ambient temperature, and likewise how fast the battery will cool once it's heated,
given a lower ambient - the heat soak effect.
Another battery heating process results from the battery's internal heating, the battery's losses (I^2 x R, I-motor current,R-battery resistance).
This heating process can occur more rapidly based on the motor current (vehicle speed) than a changing ambient temperature. The battery has
a thermal resistance to a vehicle's body, and the body has a thermal resistance to ambient. Typically the thermal resistance is much lower from
the battery to the body than the body's thermal resistance to ambient. The net effect is that the battery can heat up more quickly from its
internal losses than from a change in ambient, given high motor loads, e.g. vehicle speed. That's why without TMS, the Leaf's battery temperature
needs to be monitored while driving besides just being concerned about the effect of an ambient temperature on battery temperature,
which affects battery degradation.
