The Technology
ALP's integrated lithium ion power system incorporates a number of advanced technologies to deliver the performance, reliability and durability demanded by automobile manufacturers:
- optimized lithium ion cell design;
- cell overcharge protection;
- advanced thermal management;
- integrated power interface and safety disconnect systems;
- control interface compatible with the latest industry standards, and
- light, compact packaging.
Cell Design
ALP uses advanced high power lithium ion cells. The advantage of using lithium based cells compared to the current industry standard nickel metal hydride (NiMH) lies in the much higher energy and power density of lithium ion cells. This allows a hybrid electric vehicle battery pack to be designed to match the power and energy density of current NiMH packs, but be much smaller and lighter. ALP also has battery pack designs that match the weight and volume of current NiMH packs, but provides more than twice the power and energy. This allows a hybrid vehicle to operate for a longer period on electric power, and hence significantly reduces fuel consumption and reduces exhaust emissions.
Cell Protection System
Lithium ion batteries must be protected to avoid overcharging that can cause serious cell damage. ALP's proprietary battery management system monitors the voltage and temperature of each cell and actively equalizes its state of charge. The system uses an automotive-grade control unit interfaced with a network of microprocessors controlling the battery modules.
Thermal Management
Battery packs in hybrid vehicles undergo constant charging and discharging in response to the powertrain load conditions. Active battery cooling is necessary to maintain the cell temperatures within allowable temperature limits. From the standpoint of battery durability and reliability it is also extremely important that the cell temperature remains uniform across the entire pack. ALP employs an electronically controlled cooling system that varies the condition of individual cells to maintain a uniform temperature distribution. The thermal management system also has the capability to heat the battery after prolonged storage in low temperatures.
Power Interface
The battery power interface functions to connect the battery to the vehicle DC bus as well as to implement safety features required for a high voltage/high power system. The power interface includes contactors automatically disconnecting the battery in case of power system failure or other emergency. The electric drive system of a hybrid vehicle is fully isolated from the vehicle chassis. The power interface includes a ground fault interrupter that disconnects the battery if a ground fault is detected.
Control Interface
The battery pack controller is an automotive grade ECU compatible with the industry standard. The battery controller communicates with the vehicle controller via a CAN bus, and can be readily customized for specific platforms. ALP uses advanced model-based rapid control system development tools to minimize the time and cost of control system integration.
Packaging
ALP battery packs are optimized to ensure mechanical integrity of the system in the harsh automotive environment. The battery housing is reinforced with advanced material inserts to minimize weight while maintaining high stiffness and strength. The pack is also designed to withstand the vibration and shock levels typical in automotive applications.
Because lithium ion batteries are smaller and lighter than current automotive power batteries (generally, Nickel Metal Hydride), ALP's advanced automotive power package can provide power equivalent to current technology at a smaller size and lighter weight, or more power at an equivalent size and weight.