Battery Technology
To achieve the voltage and capacity requirements of a given application, cells are electrically connected in series and in parallel. LTC?s wide range of cell capacities generally allows choosing the right cell size to achieve the required capacity generally without connecting cells in parallel thus greatly simplifying battery design and improving reliability. For example, a battery for a PHEV might require a voltage of 300V and an energy content of 12kWh for a pure electric driving range of 30 to 50 miles. This can be accomplished by connecting only 94 LFP cells with 38Ah capacity in series.
In collaboration with an electronics company, LTC has developed an electronic battery management system with individual cell monitoring and charge equilibration for optimum life and safety (Figure 4). Over a CAN bus, this system also provides status information about the battery to the device it operates such as a vehicle.
Thermal management of large batteries is required to avoid large temperature increase of the cells and temperature gradients within a battery. This is important both for life time and safety of the battery. The amount of heat generated and with it cooling requirements depend on battery size, power requirements and cell properties. Due to their proprietary design, LTC cells have a low internal impedance and therefore low heat generation on charge and discharge. Therefore air cooling is sufficient for many applications. Table 1 lists the requirements for different vehicle applications. The BMS performs the thermal management function by measuring cells temperatures and by controlling cooling.
