I wonder what the efficiency numbers are. The retrofit will add weight to the car, but won't remove any in the form of a lighter engine. There is also no regenerative breaking, and presumably no way to disengage the engine to run purely on electric power. I also wonder, speculatively, if the power assist will interact degenerately with the existing automatic transmission--perhaps running the car in a less than optimally efficient gear.
Actually I don't see why they can't put regenerative braking in. The motors double as generators and they already have a connection running to the battery. And the motors are right next to the brakes so they could easily detect when the brakes come on.
To do regenerative braking the motors have to know when you're braking. That means hooking into the car's controls to detect when the brake pedal is pressed. It also means preventing the normal mechanical brakes from engaging while regenerative braking is being done. And it means being able to engage the mechanical brakes if the batteries can't accept incoming energy fast enough. All this is a highly non-trivial controls problem, which requires close integration with the car's control computers. I don't see how that can be done with a retrofit.
You're making the problem harder than it needs to be.
Knowing when the car is braking is trivial - the vast majority have a dedicated brake switch wire.
Why do you want to prevent the normal brakes from engaging when regen braking is happening? Since the electric motors are on the rear wheels, braking traction will be severely limited. The majority of braking needs to happen up front due to dynamic weight transfer.
Instead, use a simple brake balance controllers to reduce the mechanic braking effort at the rear and make up for it with the regenerative braking. Brake balance controllers are readily available in the aftermarket, so this is a solved problem.
> Knowing when the car is braking is trivial - the vast majority have a dedicated brake switch wire.
Yes, that would work, provided it didn't affect the signal going to the vehicle's own computer. (It doesn't seem like it should, but I spent some time as an automotive engineer, and one thing I observed is that the car will do lots of things you don't expect.)
[Edit: after seeing another comment below I'm not sure the switch would be enough; you need to know how hard the brake pedal is being pressed so you know how much braking the driver is requesting and can adjust the amount of regen accordingly. But there are ways to do that as well, as the commenter notes.]
> Why do you want to prevent the normal brakes from engaging when regen braking is happening?
Because the normal brakes prevent regenerative braking (regen) from happening. Both processes convert the vehicle's kinetic energy into something else--regen into electricity, normal braking into heat. You can't convert the same kinetic energy into two things at once, so any energy converted into heat by normal braking is unavailable for regen.
> The majority of braking needs to happen up front due to dynamic weight transfer.
Which will limit how much regen you can get, since it can only withdraw energy if it is actually slowing the wheel down. It may still be worthwhile to do regen, but not nearly as much as if you could do it on all four wheels.
> Instead, use a simple brake balance controllers to reduce the mechanic braking effort at the rear and make up for it with the regenerative braking.
Are these controllers dynamic? That is, can they adjust the balance depending on whether regen is happening or not? There will be circumstances when regen can't happen, or can't take all of the energy available (for example, if the battery is close to full or unable to accept charge fast enough).
If the controllers are dynamic, then I agree you could put together a solution this way. But you would still need to do a lot of tuning of the controls. One thing I would be worried about if I were doing this is being able to get everything tuned smoothly without having access to the code and calibrations in the vehicle's own computers.
The way the video describes the controller in the trunk, I believe it is not interfaced directly to the car. I kind of assumed it uses an accelerometer to notice the car is moving forward and engages the DC motors. If this is true, I would imagine that the same accelerometer could notice that the car is braking.
Not sure why the trunk mount is relevant for interfacing with the car. The brake switch signal activates your brake lights, those are typically at the rear of the car :)
Admittedly, for a universal application you want to interface with as little of the car as possible.
That said, in the US all cars made after 1995 comply with certain On-Board Diagnostics protocols (OBD-II) so you can interface with several standard systems.
One such sensor available in OBDII is the VSS or the Vehicle Speed Sensor. Check out a device like the Scan-Gauge[1] to get an idea of other sensor that can be interfaced with universally. It would be trivial to run some wire under the carpet and plug into the OBDII port to give the hybrid system access to all kinds of engine & sensor info.
> I would imagine that the same accelerometer could notice that the car is braking.
It would not be able to tell the difference between braking and simply slowing down, for example going uphill - or worse, driving in water - hitting the brakes when going through standing water can be disastrous.
As for the accelerometer detecting moving forward it has some nasty feedback going on there, since it detects its own motion. Plus imagine going downhill and the read engines think you hit the gas so they cause you to go even faster.
That said, it should be possible to interface with the engine there are plenty of signals that can be used (throttle, rpm, etc).
> it should be possible to interface with the engine
Agreed. I was simply saying that from what I got from the video, it is not interfacing with the vehicle. Maybe it should be but it seems that is not what they are building. I'll leave it to the people that have been working on it for 4+ years to make that decision as they certainly know a whole lot more than I do.
Yeah, or if nothing else install a button for the driver to engage regenerative braking when he knows he's going down a hill or coasting to a stop. Have the regenerative braking turn off if the driver touches the real brakes.
It seems like you'd still get 50% of the benefit and have no potential to interfere with the brakes.
> Yeah, or if nothing else install a button for the driver to engage regenerative braking when he knows he's going down a hill or coasting to a stop. Have the regenerative braking turn off if the driver touches the real brakes.
Just a button wouldn't work; how would the system know how much braking to apply? You would need something with variable input. Even then it would require considerable practice, I think, on the driver's part; it would be something like trying to control braking with the parking brake while the vehicle is in motion (which I have had to do on one occasion when my regular brakes failed--it's not at all easy).
We don't have numbers, so this is all speculation. Still, I think we can agree it's a neat idea that definitely deserves exploration.
With regards tot he transmission question: my car (and many others) allow me to select the gear even though it has an automatic transmission. In my car it's called Autostick, other cars it will be something else; sportshift maybe.
In this way, I can ensure the gear will be optimal for gasoline consumption.
Also, perhaps in the future, a model can be made to incorporate regenerative breaking.
>perhaps running the car in a less than optimally efficient gear.
A properly designed solution would enable the opposite; keeping the car in an optimal gear for longer. A hybrid works best when the batteries run where they have the greatest advantage against the fuel.
Depending on the efficiency of the implementation I'm sure (as well whether or not this is a valid study at all), but it seems that electric cars are able to do it significantly cheaper than gas. So those savings are probably not spend at the electrical outlet.
This is awesome, except for one thing. As with all hybrid kits, you lose trunk space. Unfortunately, if I can't fit my groceries as well as the stroller for my daughter, it's out of the question. Obviously not everyone requires this, but how many commuters do you think never need the trunk space?
These batteries and controllers need to find another place. On the roof of the car, perhaps, unless you're an outdoor sports person and need racks for bikes or a kayak?
They don't show any photos, but I wouldn't be surprised if the batteries don't occupy the entire trunk, especially on the production model. Obviously this would also be dependent on the size of the original vehicle as well.
He mentioned the prototype is larger than it needs to be. They needed to have easy access to data ports to pull diagnostics info from the batteries and controllers.
The size of the final version should be about the size of a carry-on bag.
The video mentions that the production ready kit will be about the size of an airplane carry-on bag. I think for most cars it's possible to fit a roller carry-on bag, a stroller, and groceries with ample room leftover.
You're just concerned about unsprung weight? What about the now positive torque applied to those wheels? That's the whole basis of how ESP works: applying a counter-force to a wheel in order to balance the car thanks to the torque generated around the yaw axis, so how does each motor knows what force to apply so as not to actually throw the vehicle off balance?
Think RWD cars. Floor it on a curve and you can go into a tailspin. But RWD cars are designed as having power on the rear while FWD cars have not, so the effect could be much more dramatic with much less force.
It's not that complex to solve... as long as you have access to the various sensors (Hall, inertia... if any) and actual decisions of the ECU, and design data (i.e everything the manufacturer has), but piggybacking on it is quite an endeavor. And it has to be done for each car model since they all differ dynamically and in hardware.
I'm not even considering collaboration/conflict between ESP and the retrofit. A car whose chassis is designed to have force applied on the front wheels only (hence with rear wheels freewheeling) may not react properly at all to rear wheels having power. From suspension to weight distribution to force transmission through the chassis rigidity.
For example (oversimplification), FWD cars have their suspension balanced to be stiffer on the rear because it gives the front more grip (and the reverse is true for RWD cars). This stiffness would not usually result in a loss of grip under load (e.g in a corner), but adding a force to the wheel may overcome the remaining grip and throw the car into a tailspin.
Applying a rotating force on the wheels creates a pinching effect, momentarily changing the parallelism. This effect is sufficiently noticeable that some cars are designed with wheels not parallel at rest, so that when you drive on the highway (and thus apply some power to the wheels) the wheels are parallel.
There are countless scenarios where things can go wrong because you're simply doing something that the car was not designed to handle.
(For the curious, the Forza Motorsports series has a nice sandbox mode allowing to experiment with various settings by changing them on the fly, and the inline help explains succinctly the impact of each knob on your car's behavior)
But these electric engines could be programmed to only run when the car is moving in a straight line. If the wheel speed between the two rear wheels starts to differ then the motors turn off.
Hybrids do well on gasoline because they have efficient undersized engines combined with light weight and excellent aerodynamics. This retrofit wouldn't change any of those things so I doubt it would have the claimed mpg benefit on a long drive. With a big battery pack, I could see it boosting MPG in city driving but it doesn't have gearing to use the motors at high speeds like highway driving. The big battery pack hurts city driving because you need to accelerate and decelerate that added mass.
It reminds me of similar retrofits that might be comparable and easier:
1) Replace the alternator (or AC) with a small 6-10hp motor. This is like a DIY version of the Honda IMA. I think GM was promoting something like this. You're limited by the power a belt can transmit, but it does go through the transmission and allows easy stop/start of the engine (ex: at a traffic light).
2) Remove the rear drive-shaft from a 4WD like a truck and attach a motor to the differential. This is also somewhat easy and a truck is better equipped for carrying batteries. There was a Jeep design that did this. Stay in "4wd" without applying power to the motor and it's like a front wheel drive. The downside is that the motor isn't geared so it's only good for one speed range (perhaps low end torque).
Unfortunately, both designs are just mild hybrids. To really go far enough with the motor you need lots of batteries. For example, the 80lb NiMH pack in my Insight can barely go a few miles. Regen makes sense but you lose a surprising amount of energy charging/discharging. I get the best gas mileage trying not to use the hybrid systems (even in city driving).
Should be "any front-wheel drive car." It looks to me that they replace the rear axle with 2 electric motors (one on each side). I don't think they could install this on a car with powered rear wheels.
I'm actually more concerned with how they've changed the design for rear drum brakes vs. rear disc brakes.
If I recall, that model Accord wagon had rear drum brakes.
edit: yep, it does have rear drums. I'm VERY curious to see how they intend to make this work for disc brakes, especially when the calipers have to wrap around that huge assembly.
The idea of rolling down the road and having a few magnets come flying off also scares the daylights out of me.
I don't see how the design could be adapted to disc brakes. The majority of vehicles sold have drum brakes on the rear, probably close to the 90% figure the person in the video mentions. Furthermore, cars with disc brakes on the back often have a cheaper trim version equipped with drum brakes, so reverting these back to drum brakes would not be overly difficult - swap out the mechanical bits and adjust the brake bias.
I would be very surprised if 90% of vehicles use drum brakes on the rear wheels (at least in the US). Every car that myself, my parents, my wife, her parents, have ever owned (except for one) has had disk brakes on the rear wheels. While I know I'm using proof by anecdote, I'm just saying I would be very surprised if it were even the majority.
Unless your parents are very young, or exclusively drove sports cars their entire life, that's almost certainly not true. Front disc / rear drum was a standard design for a long time.
You're more likely to notice disc brakes -- they are more visible from outside the car and require slightly more frequent maintenance -- so you may not be able to think of many cars with rear drums.
> The majority of vehicles sold have drum brakes on the rear
The majority of OLD cars. Modern cars are switching to disk brakes all around. The best design is actually a hybrid brake - it has a drum brake in the middle used only for the emergency brake, and the outer edge is flat for the disk brake.
Is there anyway someone could offer natural gas conversions for around this same price? That would also give you a huge savings (possibly comparable to this).
It is unlikely that a natural gas conversion could be done for this price. The tanks to hold natural gas are quite expensive and I doubt we will find a significantly better way to build a high pressure tank than we already know about.
Then you have the issue about a filling station.
Then considering taxes on fuel are nearing 50% of fuel cost, you're right around where this conversion gets you. (I don't know if NG at the pump would be taxed)
Electric solutions work around the issue of fuel cost and filling locations nicely. Electricity is cheap and basically available in every garage. If you have a garage. Having a hybrid electric works around the issues of limited range and cold weather.
I'm just thinking people would fill up at home. If nothing else use it for commuting. Most Americans already have a natural gas line coming into their house.
So charging stations wouldn't be necessary and taxes wouldn't be an issue either.
Another fine example of an IMPLEMENTATION, not an INVENTION that should not receive any patents whatsoever.
Good work, of course, but, if you tasked any capable team of engineers to build a DC brushless motor as a retrofit into a car wheel this is what you would get. In fact, there are thousands of teams all over the world that could do this inside of six to twelve months with equal results.
This is probably already patented in some way by Peugeot since that's (almost) how their 'hybrid4' (diesel+electric) work. The engine is not in the wheels but that's really not a stretch to place them there. I would be surprised it they did not try it.
Putting the motor in the wheels must produce a hefty increase in rotating mass and in un-sprung mass, both undesirable. It's necessary in the case of a retrofit, but in a from-scratch design I doubt an automotive engineer would try this.
There's certainly some downside, but the compromise can be worth it for packaging reasons, and there are a few mitigating factors.
For one motor torque scales with the square of radius, so a relatively light pancake motor can have quite high torque. You can also downsize the friction brakes thanks to regenerative braking. Finally you can distribute your motors across all the wheels.
In exchange you get a drivetrain with one moving part per wheel (yes, leaving aside bearing needles, you pedant!).
I don't foresee this making its way into sports cars, but I could see the minivan of the future having a drivetrain like this.
That video is about a show car, and it says the technology will show up in he 2010 model year. But it didn't happen.
Electric cars face big challenges in terms of cost and weight; I expect that a design like this, which increases both, is far, far away.
The Tesla cars, which cost a huge amount of money, don't do things this way. The Toyota hybrid system, probably the most developed in the world at the moment, doesn't do things this way. The people who designed those things were smart people.
When I lived in Houston, I would've loved to see a hybrid retrofit of the type the original Honda Insight had -- a motor/flywheel. That could have turned my old biodiesel Mercedes into an acceptable hurricane emergency diesel power generator.
The design decreases the efficiency of the car in total, through increase in weight, increase in mass and probably a few other things we haven't thought of. It makes up for it by allowing you to replace gasoline with electricity, which is much cheaper.
Less efficient, much cheaper, and hopefully less environmentally harmful.
I like what this solution offers - a chance for someone like me who will probably never buy a new car to easily modify an older car to run at least partially off electricity.
Electric motors are great at low speed torque which is why it helps the gas milage so much with city driving. I bet it also can take a chunk out of the 0-60 time.
The next step is to add power regeneration during braking.
If this is practical, I am sure the big car manufacturers will just do an end-run around any patent with their own tweaks and then it will just be a lawsuit battle.
