Build Your Own Hybrid-Electric Car?

BlueJay465 writes "On almost every news outlet, everyone is talking about the price of oil, both foreign and domestic. This sent me to do some research on what it would take to keep the investment in my current vehicle, while getting the added benefits of hybrid-electric technology at the lowest price. One company, Sigma Automotive, has already jumped on that bandwagon, and will soon be offering a kit for your car engine that will boost performance and increase fuel-economy by adding all the extra electronics, hardware and capacity (avail. Q3-Q4 2004). My question is, how much would it cost to really 'Do It Yourself' using off-the-shelf parts?"

Comments

Seems legit to me

[YankeeInExile]

I read through their site, and while I am vaguely skeptical of things like the lifespan of the Super Capacitor Battery Pack and I2R losses system wide the basic theory is sound.

It seems like the product right now is targetted at people who want an extra 35 b.h.p. "off the line". And if you do a lot of stop-and-go driving, that could help a lot.

In my gut, I think a fully electrical transmission would provide better systemic efficiency, but that would be nowhere near a bolt-on system. (I base that on: the specific consumption of any I.C. engine is lowest when it is near it's peak output. Any system that is predicated on running the engine at variable speed (i.e. using a traditional mechanical transmission) is going to, by necessity, run the engine most of the time away from it's peak efficiency. I would be willing to hear the argument that the gain of running the engine at peak efficiency would be offset by the losses in the motor-generator pair. (If so, why has it been the standard technology in railway traction for over fifty years?)

Re:Seems legit to me

[Waffle Iron]

I would be willing to hear the argument that the gain of running the engine at peak efficiency would be offset by the losses in the motor-generator pair. (If so, why has it been the standard technology in railway traction for over fifty years?)

I could hazard some guesses about why we don't currently see electrical transmissions in cars:

Weight: It seems to me that a motor/generator pair would probably weigh more than a mechanical transmission, which is just a few gears and/or hollow turbines. This isn't an issue on a locomotive, where heavier is better for creating traction (IIRC, some of the biggest steam locomotives weighed as much as a 747).

Power: A lot of people are used to having 300hp on tap. That's almost 1/4 of a megawatt. You'd need to have some serious power control circuits to handle that much juice. A locomotive is powerful, but pulling a train is really more about torque than raw horsepower. Electric drives do have excellent torque capabilities (and it's just about the only technology besides steam pistons with enough torque to start a freight train), but people in cars want neck-snapping acceleration. That would require a lot of copper and power controls.

CVT: Continuously variable mechanical transmissions have already been on the market for a few years. I would imagine that they can keep the engine running at a fairly constant rate. I think that they are somewhat more efficient than standard transmissions, but not by a huge factor. What makes hybrids special is that the engine produces almost constant power, not just speed, because it uses the batteries for power storage when it is generating a surplus. This allows for much more efficient operation than just a CVT. It's interesting that some of the hybrids use a mechanical transmission in addition to the electrical boost. I gather that that's because the mechanical drive was more cost-effective for transmitting that portion of the total power.

Re:Just a guess

[YankeeInExile]

Not bad ... in their own site they suggest MSRP should be +/- 2800.

Q. How much does the Electrocharger(TM) cost?

A. Estimated retail is $2800.00 USD.

Transmission woes.

[Pyro226]

The transmission would be one of the hardest things to deal with. You want the gasoline engine to be at a peak efficiency RPM as much as possible. The best way to do this in a hybrid car is to have the electric motor generate electricity when spinning the engine at an efficient RPM would provide too much acceleration, and use electricity when an efficient engine RPM isn't enough acceleration.

The toyata prius has a very special system that deals with this, as this page shows. Especially with hybrid SUV's coming out soon, building your own hybrid seems like it would be way too much work.

Also keep in mind, that right now making a hybrid car (for a major automanufacturer) costs several thousand dollars more than making an equivalent conventional car mostly because they don't have enough mass production on the hybrid parts, and they are making thousands and thousands of cars. Buying the parts individually, the price would be outragous.

illegal for NHRA racing

[doorbender]

The Internal Combustion Engine (ICE) Dragsters may not have an electric motor configured to add power to the wheels.

Re:Devil in the system

[deacon]

The vibrations come from using a toothed rubber belt (gimler belt, which is springy or elastic) to join two inertias or masses (the crankshaft and the new alternator/generator thingy.

Since the engine output is pulsed (a pulse happens with every power stroke) there is a ready supply of driving or excitation vibration which is just waiting to find the resonant frequency of the whole system.

And since the pulse frequency varies with the engine speed, you have a full range of driving frequencies to work with.

If the resonant frequency of the engine/gimler-belt/alternator system is outside the driving frequencies caused by the engine, everything is fine.

If not, the forces in the belt can become "Large"

:)

Regenerative breaking...

[the_rajah]

has nothing to do with the mechanical brakes other than that it takes some of the load off them.

Remember that any DC motor can work equally well as a generator. In regenerative braking, the motor becomes a generator providing mechanical resistance to slow the vehicle and the energy produced is fed to the energy storage device, either batteries or super capacitor where it can later be recovered and used over.

Actually this is fairly common practice in certain types of traction (cabled) elevators where the motion of the elevator car, say, up in the case of an empty cab with counter-weights heavier than the cab, actually pushes power back into the 3 phase power lines. There are no big resistors needed to consume the energy produced when the drive motor becomes a generator. This is efficient in terms of energy consumption.

Mechanical brakes on elevators are normally set only after the cab is electrically stopped and held at floor level.

"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain

Re:Regenerative breaking...

[SidV]

"In regenerative braking, the motor becomes a generator providing mechanical resistance to slow the vehicle and the energy produced is fed to the energy storage device, either batteries or super capacitor where it can later be recovered and used over."

Actually no. in regenerative braking, the motor that is attached to the wheels no longer provides power, and reverse energizes the coils, the spinning wheels then have to overcome the engine, basically running in reverse, done right this creates a net gain after system loses (Engines work better as engines than generators, and generators work better as generators then engines. Try appling voltage to your alternator and see if it spins)

to do regenrative braking as you describe, with this system is impossible, and if it were possible would damage the engine.

to continue:

Take your foot off the gas, engine slows, slows tranny, slows car, output of alternator drops. Due to the fact that engine rpm is slowing. Engine compression is MUCH higher than the resistance of the generator/engine you got strapped on the front. Net gain would most likely be negative #s
Place load on engine at crank, slowing engine more. Lets forget for just a second that at best you are going to get only 1/2 to 1/4 of that power, since only one or two wheels are connected to the engine (forgetting AWD $WD for a moment, talking about most cars). In an automatic the clutch packs will intentionally slip (remember engine can run or stop and have minimal effect on wheels, as autos are designed to only engage at accelertion speeds, and at steady state, torque converters are one way) In a manual you will be creating undue strain on the clutch. Hello unintentional slippage, glazing, loss of clutch. Not to mention that the crank is not designed to have power applied in that way. Low engine RPM's compared to wheel speed leads to broken cranksafts. A very not fun way to drive down the road.

As to a slight boost of power at acceleration. You might as well just kick the starter in, theres only so much power in the battery, if it's driving a motor, why not one you already have, why add the weight of a second motor. Regardless, the power gains are minimal here.

Particularly since after your momentary burst of accelration there will be a higher load on the alternator, sucking engine power in an attempt to fill the battery up of all the juice it just lost.

Of course I hope you have a collection of flywheels, running the starter while the engine is running is never a good thing.

Any belt drive type system, which this appears to be, cannot hope to match the powers needed to put that kind of load on the motor. Damn belt would slip like mad. Well until it snapped anyways. And that's not even considering modern serpintine systems, No way you can transfer that much power.

Railroad locomotives

[isny]

Yes, locomotives use a hybrid power system, but it's (usually) all based on electric conversion: The engine drives an alternator, and the power from the alternator drives traction motors (avoiding batteries). Dynamic regeneration is usually not used: when dynamic braking, all power from the traction motors are radiated out the dynamic braking grids as heat.

Here's better way to improve fuel mileage....

[MtViewGuy]

Redesign the engine for better fuel efficiency.

Thanks to the phasing in of low-sulfur gasoline (petrol) and diesel fuel here in the USA starting in 2005, we can apply the latest in fuel-delivery systems and exhaust emission controls to improve fuel efficiency AND reduce harmful exhaust emissions.

In the case of gasoline engines, the switch to direct fuel injection (where fuel is directly injected into the combustion chamber) could improve fuel efficiency in the range of 15 to 20 percent! :-) Thanks to the arrival of low-sulfur fuels, it means we can use the latest in ceramic catalytic converters that will also reduce exhaust emissions to Super Ultra-Low Emissions Vehicle (SULEV) levels without worries about sulfur compounds ruining the catalytic converter.

In the case of diesel engines, the arrival of low-sulfur diesel fuel means we can use common-rail direct fuel injection for very precise fuel delivery and also use the latest in diesel engine catalytic converters that will remove diesel exhaust particulates in addition to dramatically reducing other harmful exhaust gases. By switching minivans, SUV's and light trucks to these new cleaner diesel engines it means these class of vehicles can get 35-50 percent improvements in fuel efficiency compared to the current gasoline engines being used.

Re:Seems legit to me - railroads

[psetzer]

Well, let's take a look at what we're talking about. Suppose we're trying to push an SD70MAC, which produces 6000 hp at around 1800 RPM. First things first, if you want a manual transmission, this involves the mother of all clutches. Otherwise, it involves the mother of all torque converters and a truly massive set of planetary gears. Neither is very pretty. Next up, you have to get the power to what can be at least sixteen drive wheels. Oh, and they're on pivoting bogies in some cases, which makes drive shafts much more fun. Finally, you have to have an engine with a wide powerband, and the engine won't spend most of its time running most efficiently. This is because in a manual transmission, the wheels rotate at a constant multiple of the rotation rate of the engine. If the wheels are stopped, so is the engine, unless you're depressing the clutch.

The reason for having electric drive is simple once you realize the previous facts. First, there's simply a direct shaft from the engine to the alternator or generator (Trains can be both AC and DC). That means no gears at all, and no clutch or torque converter. The wires from our generator can run to the drive motors in any manner that they wish. Finally, they connect to the wheels directly, with no gearing. Note that the speed that the engine is turning is completely independent of the speed of the wheels. This allows improved efficiency, and it lets you have any torque at zero velocity. Furthermore, note that we also have maximum torque starting out, and trains really need it when someone decides to save money by putting fewer engines on a larger consist. Even though it suffers from all the inefficiency of the two conversions, it can always run at the engine's sweet spot. However, the fuel efficiency isn't as big of a problem as it seems. Once a train is rolling, they need very little power to keep it going. The fuel that is used in the engines is also not the kind of stuff that you would put in your car, or your tractor for that matter. It's like high-sulfur 30 weight, and it costs less than any other petroleum product short of road tar.