I've been doing more research on the Prius, and have discovered that the Prius has an engine coolant tank that can keep coolant hot for up to three days after the car is shut off. I also discovered that there is a small capacitor battery that enables the brakes to function normally for up to 5 minutes after an all-systems failure. I think these are very neat and innovative designs, and I curious to know, do any other vehicles boast this technology or am I just behind on the times? Of course, by now I know more about hybrids than I do about normal cars! Sometimes I talk to people and I don't know what their car's doing, but if a Prius did it, I might know!
Gen III did away with the 'thermos' to keep coolant warm and instead employs an exhaust heat recovery system. Prius is always being advanced, and yes I agree, HSD has been and still remains amazing. How does the exhaust heat recovery system work? | PriusChat
1. The engine coolant heat recovery system can be found only on 2G Prius sold in North America. It is supposed to speed up engine warmup time for exhaust emissions reduction. IMO this is an example of unnecessary complexity, except it helped to qualify 2G Prius for AT-PZEV emissions certification in California. The coolant storage tank is in the left fender in front of the tire and can be seen if the fender liner is removed. 2. Prius needs the capacitor bank (located next to the 12V battery) because the braking system has an electrically operated hydraulic pump, called the brake actuator. The brake actuator is needed because the Prius gasoline engine does not run constantly. Most cars have a traditional hydraulic braking system which receives power assist via engine vacuum (since the gasoline engine is intended to run at all times the car is operating) so #2 is not needed.
Keeping the coolant warm for 3 days sounds like a stretch to me. Is that correct? Is that only true with very hot ambient temperature? thank you
Yep, only the North American model has the coolant recovery thermos, but they all have the brake capacitor. If you think about it, the Prius had a pretty unique requirement in needing all of it's systems (brakes, power steering etc) to continue to function, even when the engine is off for extended periods of time. This is why the hydraulic system is electrically operated. It doesn't need those capacitor all the time though, even when you're gliding with the engine off it's still really just using the normal 12V power. However they put the capacitors there just as a back up, so that you wouldn't lose brakes if the car suddenly lost its electrical power from the inverter AND the 12V battery turned to crap as well. Most people will never need it, but it's nice to know it's there. Warm is only a relative term. I assume that they mean warmer than ambient, so probably barely lukewarm after a couple of days. If on the other hand you've had the engine nice and hot and then park in freezing weather for a few hours the thermos is probably very useful for get the engine back to warm more quickly.
I've noticed some owners who refuse to replace the 12V battery when it has failed and instead rely upon jumpstarting the Prius for an extended period of time. That is an example of an owner who would benefit from the brake capacitor bank if the inverter pump decides to fail and the DC/DC converter stops operating.
Yes I've noticed that too. Lets just say that leaving out the capacitor bank for those people would merely accelerate natural Darwinism.
The problem with normal vehicles not having #2 is that, if the vehicle does malfunction, dies, or the battery becomes disconnected for some bizarre reason, it is instantly extremely difficult to brake. I think this would be a great feature for any vehicle to have, in my opinion. As for number 1, that does seem a little bit too complex, although interesting. Is it just me or does sound like a really bad idea? We looked at a 2001 Prius at one point, and they had to jumpstart it to get it to turn on. I'm assuming they either screwed something up or the battery was so shot it couldn't run the poor car, because after a couple minutes of operation the car basically died, the RPMs sounded really high and the car stopped moving. They offered to load it on a trailer and send it home with us, but we really didn't feel like paying $3500 for a project.
I agree that it is a really bad idea to tolerate a failed 12V battery in the Prius for an indefinite period. Also agree that $3,500 is high for a 13-year-old Prius with unknown but likely very costly issues. (If it was so simple to repair you would expect the seller would fix the car so it could be sold at a higher price.)
No, normal cars use the engine's vacuum to boost the brakes. Since the engine is turning and thus generating a vacuum whenever you're moving, then these should be pretty safe. Even automatics these days can keep the engine rotating without fuel fuel injection when the car is slowing down. The only time it would really let you down is if you were driving a manual and for some silly reason decided to put it in neutral and coast. Then if the engine cut out you would indeed lose brake assist. Of course it goes against all good driving practices to coast a manual in neutral anyway.
