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Hybrid Vehicles Hybrid Vehicles - Archived Discussions How do Hybrids work? Newbie questions encouraged! 
139 messages, Last post on Aug 02, 2007 at 5:38 PM
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I think ABS is currently applied where it needs to be....right at the wheel. If you were to depend on IMA or HSD systems to pulse the wheels then you are going through differential, gears, bearings, belts and would work against the inertia of all the associated spinning parts and any wear and tear slop that may develop over time. The only way I can see for this to work is to also pulse right at the wheel, which would require traction motors at each axle. I think this could be a vastly better way but we don't have it yet. If you want regen at the same time as ABS, then regen might render ABS useless because the regen load on the wheel might keep the wheel sliding when it should be in its rolling cycle. |
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Engineers may or may not have deliberately disabled regenerative braking during situations where other accessories like ABS or stability control take over. If they did attempt to keep them exclusive, reason could be reliability and effectiveness of the overall system (a situation I can imagine is lack of a good feedback system from the hydraulics based pumps that controls ABS could leave the controller undecided as it tries to switch between motor and generator modes). The other issue may be “automatic”. ABS triggers on loss of traction, an instance where wheel slips rather than rotates (regenerative braking requires wheel rotation). No rotation, no regen. |
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Consider buying a hybrid? Reconsider after you learned about the long wait? Whether or not you chose to add your name to the waiting list, a reporter is hoping to hear your perspective. Please respond to jfallon edmunds.com with your daytime contact info by May 27, 2005. Thanks, Jeannine Fallon Corporate Communications Edmunds.com |
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I originally posted this in "Hybrid Tips: Optimizing mileage", but then found this forum and thought the post might be more appropriate here. I have read a lot of posts talking about how to drive to ensure that the electric motors only are on (referring to the Prius and other "full hybrids" that can drive on electric motors only), and I am a little confused about how that helps mileage. After all, the energy to power the batteries ultimately comes from the gasoline that is put into the car. From my understanding of how hybrids work, one of the main ways they get better fuel economy is by having smaller engines, and by running those engines more efficiently. However, whenever energy is converted from one form to another, I would assume that the conversion is not 100% efficient. If the gas engine was running at a similar efficiency when powering the car as when it charges the battery, wouldn't you get better mileage when the gas engine only is powering the car? I would think that when travelling at a constant speed, and with the CVT allowing the gas engine to operate at peak efficiency, you would get better mileage when using gas only. The electric motor helps mileage by providing extra power / acceleration when necessary while allowing the gas engine to operate at peak efficiency, and also by storing the kinetic energy from braking / coasting. I admit that I am not very knowledgeable about hybrids, so I was wondering if any of the experts could provide me more insight.
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Replying to: shadow11 (Aug 29, 2005 11:31 pm) |
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Replying to: shadow11 (Aug 29, 2005 11:31 pm) Here is a simple answer. You are right conversion is not 100% efficient. In a normal car none (0%) of braking energy is recovered. In a hybrid with regenerative braking some of the enegry is recovered and used to charge the batteries. Later the batteries use this recovered energy to run electic motors to provide some of the car's power. Essentially this electric power is free. That reduces the power need from the gas engine and in some case also the size of the gas engine needed. This effectively increases the miles per gallon of hybrid cars. YMMV (Your mileage may vary), MidCow
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Replying to: midnightcowboy (Sep 15, 2005 5:52 am) Thanks for the response. I realize that the electric power generated by braking is one way that hybrids become more efficient. I believe the battery also charges when you let the engine do the breaking by coasting to a stop. However, I was under the impression that the majority of charging of the battery was performed by the ICE. Is this not the case? |
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Replying to: shadow11 (Sep 19, 2005 8:58 pm) Most of the charging comes from regenerative braking. In the Prius and other cars/vehicles that use the HSD system from Toyota, there is a small motor/generator ( MG1) which also charges the battery when you are driving because it is always spinning. Many critics say this is inefficinet in that it continues to take some power away from the ICE and try to charge fully charged batteries. The Hondas ( Accord Hybrid, Civic Hybrid, Insight) use an IMA (intergrated Motor Assist) and it primarily provides battery charging through regenerative braking. In both cases you will also obtain some charging when you let off the gas and coast in your vechicle. . However, in both cases this amounts to only a small amount of charging. Good Luck, MidCow P.S. -For what it is worth I think the Prius is probably the best hybrid car. The primary reason I didn't get one was because it doesn't ot have a manual shift transmission and I really like to shift 
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Replying to: midnightcowboy (Sep 20, 2005 4:36 am) That blanket statement doesn't apply to Prius and other HSD vehicles. They are hybrids with *PERSISTENT* electrical systems. Regenerative braking only contributes a small amount of electricity with respect to how much the generator creates... which is far from small. It is 10kW, which is the same size as the current Civic-Hybrid uses for its thrust motor. With the 2006 Civic-Hybrid, that increases to 15kW... which is still considerably smaller than the 50kW Prius currently uses. Civic-Hybrid and the other IMA vehicles are hybrids with *PASSIVE* electrical systems. With them, the regenerative braking is the primary source of electricity. JOHN
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Replying to: midnightcowboy (Sep 20, 2005 4:36 am) That is a misconception. In reality, the electricity is simply directed back to the thrust motor immediately, rather than using it to recharge the battery-pack. This is surprisingly efficient, due to the way the Planetary-CVT is designed. The reason for the misconception is that people don't realize how frequently this happens. 10 times per minute is quite common, which is fast enough to take advantage of an efficiency opportunity without allowing the penalty of charging to take place. In other words, their are inefficiencies with the gas engine that it prevents from occuring. JOHN
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Hybrid Vehicles Hybrid Vehicles - Archived Discussions How do Hybrids work? Newbie questions encouraged!
