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Main > Encyclopedia > Deceleration / Regenerative Braking Mode

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Energy flow from wheels to battery
(via electric motor/generator)
white.jpg (631 bytes) Start-up
bullet.jpg (930 bytes) Regenerative Braking & Fuel Cut
Idle Stop (engine off)

During deceleration, the gasoline engine is switched into fuel cut mode, and the IMA Motor/Generator is operated in generation mode. In this mode, the IMA Motor is driven by the wheels, generating electricity to be stored in the Battery Module, and slowing the Insight in the process. The amount that the IMA Motor slows the car is in proportion to the amount of regeneration being done. There are two deceleration modes:

  • Foot off throttle but not on brake pedal - In this mode, the charge/assist gauge will show partial charge, and the vehicle will slow down gradually.
  • Foot on brake pedal - In this mode, a higher amount of regeneration will be allowed, and the vehicle will slow more rapidly. During light brake pedal application, only the IMA Motor/Generator is slowing the car. With heavier brake pedal application, the conventional friction brakes also come into play.

When decelerating, regeneration will continue until engine speed falls to about 1000 rpm. At this point, the driver will typically shift into neutral. In many cases the gasoline engine will now immediately enter auto idle stop mode. If vehicle speed is such that it isn't clear whether the driver will most likely come to a stop, the engine may idle for a few moments before entering idle stop. If the battery state of charge is very low, idle stop will not be entered at all, and instead the engine will continue to run at a fast idle to recharge the Battery Module.

During generation, the AC produced by the IMA Motor/Generator is converted by the MDM into DC, which is used to charge the Battery Module. The DC output of the MDM is also applied to the DC-DC Converter, which reduces the voltage to 12v. The DC-DC Converter's 12v DC output is supplied to the vehicle electrical system. It is also used to charge the 12v battery as necessary.

When the State of Charge of the Battery Module is at its maximum level, generated electricity is only delivered to the 12v accessory system.

When the ABS system is controlling wheel lock up, an 'ABS-busy' signal is sent to the MCM. This will immediately stop regeneration to prevent interference with the ABS system.

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