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Help on EV

3631 Views 14 Replies 7 Participants Last post by  zemon1
I am trying to build an EV.

I want a top speed around 150 - 175mph
I am going to construct most of the car from Carbon Fiber
I want the car to plug into a regular U.S. 110v socket
I would like to use Li ion batteries.
I also want a range of 200-250 miles
i would also like to implement Regenerative Braking

I have the carbon fiber under control but everything else i would like some of your help figuring out.:confused::confused:

Thank You,
Jeff H.
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Hi Jeff,

That sounds like a fun (expensive!) project.

Achieving speeds like that is not impossible in an EV, BUT... your vehicle will need to be very light (sounds like it will be), very aerodynamic, have very low rolling resistance, and you'll need very high voltage to achieve that sort of performance.

Having said all that, the amount of lithium batteries needed to propel the vehicle to a 200-ish mile range at typical freeway speeds will probably last just long enough to accelerate to 175 mph before needing to be recharged.

The faster you go, the more energy you pull from the pack. For example, if you drive 40 mph and want to go 80 mph, the air resistance on the vehicle will quadruple even though the speed only doubled. To go the next step from 80 mph to 160 mph, it will quadruple again. As such, each time there is a doubling of speed, there is a 4x increase required to reach and sustain that speed. This is why a Bugatti Veyron requires a 1001 horsepower engine, otherwise it would never reach its top speed of about 256 mph. It will likely consume 4x the fuel to go 256 mph than 128 mph.

Your goals are not impossible, are not cheap, and sound like a heck of a lot of fun. Please let me test drive it when it's built. :) I love fast cars.

Edit - one last thing I forgot to mention. Today's cars using lead acid batteries take as much as 10-12 hours to charge from a 110v socket, depending on depth of discharge and overall capacity. Those same cars typically do less than 40 miles range when they require that long to charge. If your car can do 200 miles per charge, then a standard 15a 110v socket may require 50 to 60 hours to recharge from "empty".

The more volts and amps you can feed the charger, the faster you can 'fill up.';)
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I already answered the question about how to charge faster. :)

The more volts and amps your circuit can sustain the faster you can pump energy back into the batteries - at least to the point of sanity for your battery type.

In the US, everyone has at least single phase 220v feeding their homes. Stuff like your clothes dryer, oven/range, water heater, etc run at these voltages typically. Most houses are fed with about 100a or more at 220v, so it would be no issue really to charge at 220v 30a if your charger and batteries supported that. That would "fill-er-up" about 4x as fast, give or take, again depending on if your batteries can take that fast of a charge.

It may be possible to make a car do 170 mph for 20 miles, but that would be a LOT of battery weight (even with dense LiFePO4 batts), and to get the type of acceleration one would expect with a vehicle that can do that, you're going to need batteries that can discharge fast enough to supply that much power.

Most EV conversions, and even those that are built from the ground up have horsepower ratings of less than 200 HP peak with less than 50 HP continuous. Neither of those figures will get you to 170 mph, even likely with a very slippery aerodynamic design with low weight. Take for example the Ferrari Enzo- since you brought up italian supercars and carbon fiber :) It produces 651 HP peak, and weighs under 2800 lbs.

LiFePO4 batts are lightweight, but I wouldn't be surprised if you needed 2000 lbs of them to accelerate to 170+ mph with any italian supercar-like swiftness and stay there for 20-25 miles. And 2000 lbs of LiFePO4 batteries will set you back the cost of an italian supercar. ;)
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