Possible help / ideas?

1961 Views 8 Replies 7 Participants Last post by  laviolette
Hi everyone,

I am a Electrical Engineering student at Marquette, and in my senior design course, our group is in charge of converting one of our Student Safety Vans (Ford E-350 XL Vans) to an EV.

We have lots of ideas swirling around, and some factors that make this conversion very feasible:

120 mile range
35 mph max speed
11 hour run time (so approx. 12 hours to charge)

Right now we are debating what type of motor to use (DC / AC, with regen?), what battery technology to attempt to pursue, and motor controllers.

If anyone has any ideas / suggestions / calculators / tips, that would be greatly appreciated. I can provide more info if necessary, but wanted to keep this short and sweet to start.

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kittydog42

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I can't see you getting 120 miles of range under any condition, at least not using flooded lead acid batteries. The vehicle is too heavy. You will also lose range due to the automatic transmission. The best of conditions would be something like 48 6V batteries, connected in 4 parallel strings of 12 for a system voltage of 72V. 48 batteries would take a long time to charge.

WahooWon

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Right now our plans were to remove ALL old components (gas tank, engine, trans) and just do a direct connection from the motor to the drive shaft, with gear reduction as a probable step.

Would 120 miles still be unfeasible?

kittydog42

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I still don't think that it will cover 120 miles. The amount of lead in 48 6V batteries calculates out to over 150 miles (22lbs of lead = 1 mile as a simple calculation), but there are a lot of other factors that reduce this, most notably hills and poor aerodynamics. I think that it will also be difficult to accelerate that van with a 1:1 drive ratio and a 3.71 final drive. Now, keep in mind that everything that I am saying applies to a DC system.

With an AC system, you can achieve much higher RPM's and efficiency. You need higher voltages though, such as wiring the 48 6V batteries in series for 288V. AC systems also have regeneration as a standard part of the system. The systems are much more expensive but I think that with an AC system, 120 miles could possibly happen.

If you had 288V, you could consider trying to use an industrial 208V TEFC motor rated to 3500rpm with an industrial 208V VFD. You may be able to easily find surplus varieties of these items. Many VFD's will accept voltage directly on the DC buss and convert this into AC 3-phase for the motor. You could possibly run the motor up to 7000rpm by setting the maximum frequency to 120Hz. I think that this setup also offers regeneration by it's nature. This is an idea that I have had for some time myself.

Any which way, you are looking at big money to do this.

John

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A rule of thumb that I used when evaluating posible EV conversions with flooded lead acid batteries is that if 30% of the final vehicle weight was batteries it would have a range of 60 miles so 120 miles would equate to 60% of the converted vehicle needing to be batteries. Taking the final conversion settled on and punching it into one of the EV calculators revealed this rule of thumb to be rather optimistic. Your low top speed will help your range but the van aerodynamics wont. Another rule of thumb I used was that the vehicles weight post conversion would increase by the weight of the batteries ie. the weight of the mechanical components removed would roughly equal the weight of the electrical components installed minus the batteries. So the batteries would need to weigh 167% of the vehicles curent weight to make up 60% of the final total weight. That must be starting to push the boundaries of what is even posible.

KDas

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Hi, guys!

You all are talking about bad Cx for bus. May be it'd be possible to improve this parameter by adding some plastic constructions and create futuristic disign for this bus? I do not think that it will be to much heavy and costly but will look like fast trains in France or Japan

Just add some fairing in front of a vehicle. Somewhere in inet I saw something like that in addition to standard front construction. It was offered especially for improving Cx.

BUT for 35 mph the performance of this fairing will be under the question. As I see bad Cx has its influance above this speed.

Just an idea...

WBR,
KDas.

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Greenflight

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Yeah, that's quite a conversion cost! It was built buy Ford, GE, and the DOE, though. i.e., an amateur could probably do it for 50 grand...

Also interesting to note that the logic circuits were removed from the controller...

laviolette

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Hi everyone,

I am a Electrical Engineering student at Marquette, and in my senior design course, our group is in charge of converting one of our Student Safety Vans (Ford E-350 XL Vans) to an EV.

We have lots of ideas swirling around, and some factors that make this conversion very feasible:

120 mile range
35 mph max speed
11 hour run time (so approx. 12 hours to charge)

Right now we are debating what type of motor to use (DC / AC, with regen?), what battery technology to attempt to pursue, and motor controllers.

If anyone has any ideas / suggestions / calculators / tips, that would be greatly appreciated. I can provide more info if necessary, but wanted to keep this short and sweet to start.