Recently purchased a Prius and have a question on the braking system. When going down hill if you just take your foot off the gas do you get full regenerative braking or are you only using MG1? Do you actually have to slightly touch the brake pedal to engage MG2 and get the full reclaim of energy? If the latter how do you know when MG1 is generating versus when MG2 is doing it?
Regenerative braking and coasting emulation is done by MG2. MG1 charges the battery through ICE power split off through the power split device, which is essentially a differential configuration. If ICE isn't running, MG1 does not come into play. Coasting does provide minimal regenerative current, as displayed in the energy display. Below a certain speed (about 7MPH in my book), the system switches to creep mode, where MG2 is used as a motor. If you look at Atilla's analysis, you'll see that you get more energy capture by slight braking, that is light pressure on the brake pedal. http://www.vassfamily.net/ToyotaPrius/CAN/brindex.html
