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Old 05-05-2009, 02:52 AM   #1 (permalink)
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DIY hybrid (detailed noodling of crankshaft-mated electric assist method)

I have an idea for a DIY hybrid conversion:
* Start with a car with a small engine and a manual transmission, maybe a small pickup truck.
* Add a motor (a small forklift motor, perhaps?) and attach it to the crankshaft with a motorcycle-type chain or a strong belt.
* Since brushed DC motors don't work very well for regen, regen will be implemented with a heavy duty alternator modified to operate at the hybrid system voltage and with a control signal from the control electronics.
* The original alternator will be replaced with the modified one and a DC/DC converter used to keep the 12v system working.
* The electrical drive system will be under independent control (Insight manual-style) to allow the driver to choose gas or electric power.
* A relay will be used to turn off the engine for EOC and EV mode.
* A panel with switches and indicators will be added to allow the driver to manually manipulate the operation of the hybrid system.
* Since it's a hybrid, the electrical system does not have to be very powerful. 96v or even 48v should be enough.
* An additional spring will be added to the accelerator to provide a clear indication of the most efficient engine operating point, above which power should be obtained from the electrical system.
* Since the crankshaft speed will vary greatly, run the power steering from a motor (maybe a vacuum cleaner motor?) under electronic control. The power assist will be greatest when stopped (maybe indirectly sense load using current to save energy?) and ramped down as speed increases. (For what it's worth, a 120v vacuum cleaner motor will start to rotate with just 12v, so it might perform well enough at 48 or 96v for our application.)

The most complex part will likely be the control electronics. It will, for instance:
* Be based mostly around hardware for easy development and reliability.
* Coordinate the transition between gas and electric power. The car could start on electric power alone, and if the driver chooses, the engine powers up once it reaches a minimum operating RPM.
* Manage the main battery pack. In normal mode, it will restrict the amount of power, but in EV mode, it will allow as much as the hardware is capable of. That is done to reduce resistance losses in the batteries.
* If the brake pedal is depressed, disable electric assist and maybe automatically regen at the optimum rate, while allowing the driver to fine tune the amount with the control lever.
* In EV mode, maybe tap into the TPS to allow the accelerator pedal to work.

Some issues are:
* Would turning the engine at low speeds be a problem? Maybe an auxiliary oil pump should be used to ensure lubrication at all speeds? (How does the new Insight solve that problem?)
* Would the engine have enough friction to greatly affect EV mode performance?
* Would the motor have enough friction to greatly affect normal (hybrid) mode efficiency? Maybe a one way clutch can solve this?

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Old 05-05-2009, 09:41 AM   #2 (permalink)
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It sounds like a pretty descent setup. Very early IMA like. Those engines didn't have an EV mode. I'd think mainly due to engine drag. The clutch idea may be a problem because it would have to handle some pretty high torque at low rpms.
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Old 05-05-2009, 12:44 PM   #3 (permalink)
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Put your motor after the trans, and use the trans in neut to remove engine friction from the equation.
The engine can be OFF and the truck will drive under electric power until you decide to use gas. No oiling worries either.
For short trips you would use electric alone and for longer trips you could switch to gas when pack voltage got too low,
Then use the gas engine to charge the batteries while you were on your way to Grandmas house.
Once you reach Grandmas, you then have a full pack to run around town and get the can of cranberry sauce you forgot.
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Old 05-06-2009, 12:56 AM   #4 (permalink)
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Nice Metro! Very good idea
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Old 12-05-2009, 11:50 AM   #5 (permalink)
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Other hybrid ideas could include using a 4-wheel drive vehicle with the original engine going to two wheels, and an electric motor added to the other.
That would be a "thru-the-road" hybrid.

Another variation would be a rear-wheel drive vehicle with the drive-shaft modified for an electric motor to be put in-line with it.
NetGain (NetGain Motors, Inc. Home) has a system like this designed for automatic transmission pickup trucks, which uses an electronic box connected to the OBD2 for controlling the throttle.

If the same idea was applied to a manual transmission S10 or Ranger, it could be a very efficient vehicle. I am not sure what the best was of controlling the throttle would be though.

One that I have thought about for a while would be something like a 4x4 Geo Tracker. It has a reasonably small engine for good fuel economy. The motor would be hooked to the other two wheels opposite of the engine powered ones.

I don't know what all the details would be for actually attaching the motor (I'm not much of a 4-wheel guy...) but it could be a cool little vehicle.
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Old 12-18-2009, 07:58 AM   #6 (permalink)
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That NetGain solution looks quite good. It's a shame it doesn't do regen though. I wonder what the benefit would be of using it purely as a regen system. By this, I mean not using it as a PHEV. Using the same motor but super capacitors for short-term storage. A controller would be needed that, for example, instigated regen at 0% throttle and added power at >15% throttle. Quite simple logic and would recoup some lost energy. The idea being that you get similar/better short-term performance to a faster model, with slightly better (?) economy than the base model you start with.

Taking a BMW 318d as an example, an extra 100bhp brings it up to similar power to the 335d, yet economy would still be as per the 318d. 6kg of Maxwell supercaps will give you enough juice for 100bhp for ~1.5 seconds. Alternatively, A123 lithium cells will give you 100bhp in 23kg for ~2 minutes, so make that ~1 minute for 50% DoD.

Thoughts? Any ideas how you'd get a controller that would work in that fashion? Admittedly, I'm unlikely to try it out!
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Old 12-18-2009, 11:32 AM   #7 (permalink)
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To get the most miles out of every kWh and gallon, you want the car to be as small and aerodynamic as possible, so hatchback > pickup. You should pick a car that can be converted to manual power steering, since DIY electric power steering is reinventing the wheel. Manual brakes are a bonus.

You should read about Mike Dabrowski's DIY through-the-road hybrid, which is a hybrid of neighborhood electric vehicle and 1st gen Insight. It's simple, easily reversed, and if something goes wrong with it, the car's original powertrain is unaffected.

You should carefully consider what you want to do with regenerative braking, and how often you'll use it. Hypermilers who have the road to themselves seldom brake. I, OTOH, use regen in traffic and highway offramps every day. The regenerative braking on the Insight is 10KW. It'll have to do, but I wish it were stronger/faster.

Quote:
* Would the engine have enough friction to greatly affect EV mode performance?
Yes. Just look at how fast your car slows down in DFCO vs EOC.
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Old 12-18-2009, 01:27 PM   #8 (permalink)
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Quote:
Originally Posted by RobertSmalls View Post
You should carefully consider what you want to do with regenerative braking, and how often you'll use it. Hypermilers who have the road to themselves seldom brake.
That's true if you drive mostly in the flatlands. Those of us who live where there are significant hills tend to use the brakes a lot more.

I'd really appreciate a hybrid that had enough battery capacity to collect the excess energy from a typical (for me) descent of 2500-4500 ft, and use it on the uphill. (The Insight will recharge completely in about 1500 ft of 6% grade.)
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Old 12-18-2009, 04:55 PM   #9 (permalink)
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Why not just use an AC motor to begin with and get regen automatically?

Something similar to what you described has been done by coyote X here I believe, on his metro. But I don't think its finished.
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Old 12-18-2009, 05:19 PM   #10 (permalink)
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Throttle control
Motor controller reads the Throttle position sensor. In EV it won't squirt any fuel into engine. In ICE mode it wont apply any voltage to motor. More importantly you don't have to figure out where to mount it.

AC
AC motors like to run at a specific RPM. It may be desirable to mount this before the transmission. I would think you would need a fairly stout power inverter to generate AC, but don't know boo about them.

Don

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