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Old 07-19-2010, 07:54 PM   #1 (permalink)
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Electric Assist Project: E-charger (2000 Subaru Outback)

The What: An electric motor assist with PHEV capabilities.

The When: Should start work in the next month. I plan to get the batteries with the next paycheck and the motor with the one after that.

The Why: Partly for fun, partly for fuel saving, partly for just outright doing something that hasn't been done before.

The How: Less than 5000$

And begin..

OK, after some research, I've started saving up my pennies (and nickles, and dimes, and quarters, and dollars..) to buy the necessary parts. Here is the current plan:

Start off with 8, 6Volt Trojan T105's that I can get locally for a good price, giving me a 48V 225AH pack. These will fit in my trunk area without limiting too much space, and I would still be able to access the spare tire well. I plan to keep the car as functionally stock as possible with this project. And Subaru's are very annoying if you don't have a full sized spare with you. (Ask me how I know that.) Ideally, I'd like to cover up the batteries with something like a fake sub-woofer box to hide them, but that's way down the line.

With the batteries in the back, an independent throttle somewhere in the cabin (Thinking the gear shifter right now, but nothing certain) I plan to get an electric motor from Thunderstruck EV, and am considering to attach it to one of 3 points:

1) Chaining it into a half-shaft and powering one wheel with the motor. This is what Coyote X has done with his Metro, and it was shown to work.

2) Bolting it between the drive-shaft and the rear differential. This is what the Eco+Muscle project did on there similar project, and it was also shown to work. The only plus side I see here is power would go to both rear wheels versus 1 wheel using method 1. Both of these methods have a problem with proper gearing (An important aspect in WV, both of these methods would essentially have a 1 speed transmission, I either wouldn't have enough power for hills or I would run out mph on the highway and over rev the motor) which leads me to option 3..

3) Attaching it directly to the engine via a drive belt. A sort of "Electric Supercharger" This would be the most practical, but probably least efficient method. (Since the stock engine would still have to spin up to RPM X to get me moving, according to scangauge this max's out around 100 mpg, but in neutral I've seen as high as 400 mpg). Essentially, the car will be driven normally, but with the assist it will drive as if it's always going downhill. This method is probably what I will be going for. I was worried that the belt might not be able to handle the power at first, but I realized that a parasitic drag of a supercharger is anywhere from 25 to 100 HP, and that power is transmitted via a serpentine belt. If that much power can be transmitted via a belt, why couldn't it work in reverse?

Using either of the first 2 methods, I was worried that gearing would be a major problem. I would either not have enough gearing to go up hill, or I'd have to find a way to disable the motor after XX mph. Using method 3 I still get to keep full use of the stock transmission, giving me proper gearing at all times.

Here is a picture of a similar engine bay to mine, that someone added a supercharger too:





The e motor would be roughly the same size, so assuming I can get a proper sized pulley on the motor, it should be good. I'd also plan to power the crank directly with a 3rd belt instead of powering it off of the P/S pump as shown in the picture. In fact, the person who did the above later used the same method!



Lots more piping and things in this picture though. But you can see what he's done still. He says it works well and he's completely satisfied with it after many miles.

One last thing: I can't simply put the car in neutral and go around with the engine off, the transmission's clutch pack will not accept it and will burn up in just a few miles.

Any questions or comments from you guys? I'd like to have at least someone tell me this idea could work.


Last edited by brucey; 08-04-2010 at 04:45 AM..
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Old 07-19-2010, 10:06 PM   #2 (permalink)
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It could work - BUT, 500+ pounds is a lot of extra weight to be carrying around all the time. And if you put all the batteries in the back, your vehicle might be a little tail-heavy. You might need helper springs or higher-rate springs in the back. And watch it on the curves!

I highly recommend Mike Brown's book Convert It! as a great guide. He shows how to build an EV safely, and what he says should apply to what you're trying to do also.
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Old 07-20-2010, 07:34 AM   #3 (permalink)
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It will work, and it will be a lot of work.

I don't like option #1. Too much problem with suspension and the drive axle moving around on you.

What motor were you thinking of using?
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Old 07-20-2010, 11:28 AM   #4 (permalink)
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Option 3 is the better, and I can explain why.

Less fabrication, and almost no modification of the vehicle. Simple is sometimes much better, and generally more user friendly.

You have to use the transmission anyway; as you said you can't go around in neutral, BUT you could get most of the benefit of coasting with the engine off with the electric motor in place of a supercharger.

As you likely know, when the vehicle is coasting in gear, the fuel turns off. Breaking that down, your throttle position sensor reads 0, your vehicle is in gear which keeps the crank turning, so the computer turns off the fuel. If you had an electric motor helping to keep the crank turning for longer you would be able to have extended coasts with no fuel being burned, which is equivalent to coating with the engine off.

Since the only scenario where the fuel would go off would be during 0 throttle, a switch could be wired to activate the motor when the throttle is at 0.

Option 3 also means you'll only need a limited rev range for the electric motor, which is right in its ballpark.

And with the correct sized belt, they are capable of handling extreme torque and power. Many industrial motor applications use belts to transmit power, and generally do a great job of it. Somehow I doubt you'll be needing all the power a good belt can transmit.

Obviously there are huge gaping holes in how to do it, but with the EV community alive and well here, I doubt it'll take long to learn what is needed.

Good Luck. I've been thinking about doing the same exact thing myself.
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I think you missed the point I was trying to make, which is that it's not rational to do either speed or fuel economy mods for economic reasons. You do it as a form of recreation, for the fun and for the challenge.
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Old 07-20-2010, 11:46 AM   #5 (permalink)
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some cars, like an alpha romeo I recall, have the transmission in the rear. So that adding an electric motor between the clutch and transmission is relatively easy (sprocket).
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Old 07-20-2010, 01:47 PM   #6 (permalink)
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Patrick: I regularly carry upwards of 1000 lbs inside the car, and in highway driving it seems to cancel itself out with pulse and glides. I know in the city my mileage will be worse, but the battery pack should pay for itself then. (: The car already has heavy duty overload coils in the rear, stiffer struts all around, and upgraded swaybars front and rear, so I know it can handle the weight.

Daox: Yes I know it will be but a lot of work sounds fun to me. (: I plan on going with the AC12 from Thunderstruck. They recommended I go with 72V with the motor, but I'm going to try 48V first to see how it goes. 72V would be a problem with my goal of keeping the car functionally stock (Don't know where I'd set the 4 extra batteries) I also know I could probably get by with a smaller motor this way, but I really wanted regenerative braking and for the system to be able to pull it's own weight. Looking around, it looks like the only thing I'll have trouble making myself will be the pulley on the motor. I might have to find a machine shop to match the splines to a pulley to connect to the crank. The motor is good for 7000 RPM and my stock engine maxes out at 6000 RPM, so to match them up I'm going to go for close to a 1:1 drive.

Shadetree: Watching the scangauge, at low speeds (<40 mph) it is very hard to get my automatic to go into fuel cut. It's also downright impossible to get it to fuel cut with the A/C on, but that's rare that I use it anyway. But when the engine does go into fuel cut, the electric motor is going to have to move the weight of the car AND turn over the (not running) engine it might be a bit much power to ask of it, which is why guessing from the scangauge, the motor will still spin up to accelerate but be using very little fuel. Even with the the throttle closed I still don't always see fuel cut unless I'm decelerating. I can go down a mountain and will gain speed and hover around 100 mpg. This is true from about 35 mph all the way up to 75 mph. Even though I'm gaining speed, the motor has to use more fuel to spin the motor up to X RPM. It might take some getting used to, but I do plan to have 2 independent throttles. This also has the nice ability that anyone can drive the car, I'll just have a switch that I can turn the E-drive off.
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Old 07-20-2010, 02:27 PM   #7 (permalink)
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Just a thought. If you do somehow wire it so that when the engine cuts fuel the electric motor takes over, be sure to turn the electric motor off when braking.

Also, not sure how you are going to get regen braking in this scenario.

Good Luck!

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Old 07-20-2010, 04:30 PM   #8 (permalink)
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Quote:
Originally Posted by brucey View Post
One last thing: I can't simply put the car in neutral and go around with the engine off, the transmission's clutch pack will not accept it and will burn up in just a few miles.
Why? Is this a regular clutch or part of the 4WD system?
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Old 07-20-2010, 05:04 PM   #9 (permalink)
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If you really want regen, you should have it so it can capture the max amount of energy. I'd avoid the engine accessory belt setup.

Also, why not go with 6 - 12V batteries?
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Last edited by Daox; 07-20-2010 at 05:14 PM..
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Old 07-20-2010, 05:22 PM   #10 (permalink)
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I've thought about this (but haven't done anything) and came up with a few possibility:
1- mount it where the AC compressor used to be, easier for me than you, as my compressor is in a box in the spare bedroom. There are a lot of complications with this, and you seem to have spotted most of them. And I don't really know if that little belt is idea for transferring more than 5hp

2- mill gear teeth into your brake disks (2 or 4 of them) and mount a little brushless motor to you strut mount. This would require a lot of machining and you would only be able to gear it for the highway, but that might be okay...

3- (the one I'm considering at the moment, if only I had the $$) A electric assist boat tail trailer. Two birds with one stone. It would be a little hairy having a trailer pushing your car, but with the right linkage it could work out. This idea needs much more planning.

Edit: Speaking of boat-tails, can you hit me up with a link to your boat tail thread? I found it via google some time back, but I just skimmed it then. never mind, found it.

For manual controlling of the motor; I was thinking a T-handle throttle from a boat would do the trick (and with style), with a switch to put it into a charging circuit for slowing.


Last edited by Dr. Jerryrigger; 07-20-2010 at 06:22 PM..
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