Jed Rothwell wrote: > Edmund Storms wrote: > >> A point you all seem to miss is that the ICE must be large enough to >> move the car at normal speeds, including up hills when the batteries >> are dead, in addition, it needs to have some extra power to charge the >> battery at that time. > > Well, it would not need to recharge while going uphill. You can leave > the batteries flat for a while. > > In the Volt, I believe electric motor drives the wheels at all times, > and the ICE connects only to the batteries.
Exactly. I have never seen this mentioned, but in principle the design could be described as very "de-coupled", or "modular". A Prius is like a rabbit -- those long ears are the temperature control system as well as a major hearing assist. You can't change one without affecting the other (not a good design, by human standards -- it makes it too hard to maintain). Similarly, in the Prius, the electric motor is also the generator which is used to recharge the batteries, the transmission does double duty as the pass-through coupling when it's in motor/generator mode, and the whole powertrain is a monolithic nightmare -- or so it appears looking in from the outside. Could Toyota "easily" bring out a diesel Prius? I have no idea, but it's certainly not a "given". Conversely, in the Volt the ICE *just* drives a shaft which turns a generator. It should be easy to replace the ICE with just about any other engine, of any sort, which fits the form factor. You'd also need to change the gas tank if you went with something *totally* different but you still wouldn't need to touch the rest of the car. The generator is *just* a generator, and just charges the batteries. You could replace it with a different model without affecting the rest of the power train. The electric motor is *just* an electric motor. You could put in a bigger one or a smaller one or a totally different design (within the constraints of the motor control system) without affecting the charging system (er, except for the regen braking system ... but that could be dropped on the floor, at the penalty of ~ 10% or 20% battery-only range loss, and everything else would still be fine). Similarly, the batteries and charging system are designed to operate like a conventional car's batteries and charging system. There is no difficulty with "tuning" it to make better use of a wall-plug -- it's already set up that way. When you read how people converting Prius's to plug-in use sometimes add whole parallel battery systems, with the "new" system being charged from the wall while the "old" system goes on being kept at full charge by the motor, you realize that there are some serious issues with the integrated monolithic design of the electrical and charging systems in the Prius. Trying to get the onboard charging system to let the batteries *run down* under certain circumstances is apparently not trivial -- and if you can't do that, then you get home with a full charge and there's no point in plugging it in! > So if the batteries are flat > and you are going up a steep hill at a high speed, my guess is the ICE > works as hard as it can and the batteries stay flat. > > When the Prius batteries are low, the car is sluggish on steep hills and > the engine makes more noise than usual, but I have never had trouble > keeping up with other cars at highway speeds in the Carolinas and > Georgia where people drive ridiculously fast (like 85 mph in a 70 mph > zone). There is a very steep, long section of highway on Rt. 77 north to > Rt. 80 (North Carolina to Virginia) that I have often driven, without > difficulty. > > - Jed >
