The Denver Regional Transportation District (RTD) is replacing the lead-acid-battery storage system in ten of its CNG series-hybrid buses with a Nickel Metal Hydride (NiMH) battery system from Cobasys, the NiMHax 288-120.
The buses are part of a fleet of 36 mall shuttle buses built by TransTeq (a Denver company), that use a Ford 2.5-liter, 70-hp, 4-cylinder CNG engine as the genset for the electric motor and batteries. (Diagram at right, Click to enlarge.)
Cobasys retrofitted two of the lead-acid-based buses for testing more than a year ago. The buses have performed over a wide range of temperature conditions during this time. Successful testing yielded improved performance and a marked increase in operation uptime.
The NiMHax 288-120 is a two-system parallel package (two NiMHax 288-60 systems) that utilizes Cobasys high voltage Series 1000 NiMH battery modules to provide a nominal voltage of 288 volts and 120 kW of power.
A complete battery system, the NiMHax 288-120 includes: the battery management system, thermal management system, and CAN communications.
Denver RTD introduced the fleet of mall shuttle hybrids in 2000. Each bus can carry up to 116 passengers.
Cobasys is a joint venture between Chevron Technology Ventures LLC, a subsidiary of Chevron Corporation and Energy Conversion Devices, Inc.