Open EV thread. Ideas, debates, questions, all good here.

[trukr]

I am by no means an expert on electric vehicles. But I feel I've done enough research to guide my personal build. So with that little disclaimer out of the way, let's transfer the discussion started on the tesla thread over here.

Like the title says, all EV related curiosities, quandries, questions, confrontations, concepts and conflicts are welcome here.

Personally, I take the stance that EV's can save you money in the long run. Eventually we won't have a choice anyways, so the sooner we start looking into it the better. Plus it's possible to do a monster EV build that'll go toe to toe with the italians.

[trukr]

I'll start with a monster that makes my build idea look like an afx slot car.

The Rimac concept-1

[trukr]

Cows chasing RC's also welcome here.

[trukr]

EV primer

A little primer on the EV stuff.

DC motors are the go to motor for the DIY guys. They use brushes that need to be replaced periodically. Regenerative braking is not really an option. The system of choice for power on a realistic budget. Very good available options for controllers.

AC motors are the engineers darling. The choice of OEM's. No brushes, so no wear items to maintain. Regenerative braking capable. Higher efficiencies. Fewer options with conroller/inverters. Huge jump in budget to get to the power set ups. It's the way to go to get the most efficient car possible. Then you get obsessed with efficiency, weight, rolling resistance, aerodynamics blah, blah, blah. You end up with a car on bicycle tires that looks like a wind turbine with the prop missing.

Lead acid batteries or floodies as they're affectionately known. Low power density, terrible efficiency and cold weather performance. Abysmal cycle life. Very affordable. Good enough to get you in the game, but generally too heavy to get any kind of decent range.

LiFePo. A form of lithium batteries considered to be the safest chemistry for vehicle use. Not the same type as laptop catch on fire batteries. Higher initial investment, but cheaper in the long run because of its greatly improved cycle life. Less weight, more power.

Battery C rating. It's the safe charge and discharge rate of a battery. You can multiply a batteries effective power deliverey by it's C rating. A 100ah battery with a 2C continuous 10C peak rating becomes a 200a continous 1000a peak battery in terms of power delivery, NOT energy storage. C rating does not improve the energy storage, it multiplies the ability to deliver and accept energy.

[FUGAZZIDESIGN]

Nice thread! now we need some people showing setup's Im in the early stages, as soon as i have something to show i will.

[MacGyver]

I don’t have much knowledge on this subject but am very interested. Please keep the info coming.

[mr. K]

i've had the privilege to take part in a cursus about a hybrid car. the volvo v60. basicly, the main problem with electric cars, is batteries. you cant fill them up in a minute like petrol, wich makes it alot less attractive, but mostly, the weight and size. those batteries are seriously heavy, wich is not good for performance cars, but those things are so big, that the chassis has to be redesigned. for a space frame build, it can be done, but to modify a existing car, is nearly impossible.

[trukr]

i've had the privilege to take part in a cursus about a hybrid car. the volvo v60. basicly, the main problem with electric cars, is batteries. you cant fill them up in a minute like petrol, wich makes it alot less attractive, but mostly, the weight and size. those batteries are seriously heavy, wich is not good for performance cars, but those things are so big, that the chassis has to be redesigned. for a space frame build, it can be done, but to modify a existing car, is nearly impossible.

There are quite a few existing conversions already, but you are absolutely correct about the difficulties. The conversions have limited room for batteries and therefore suffer from limited range. 120 or so miles seems to be the upper limit, 60 to 70 seems to be the norm.

I've been factoring a good 6 to 8 inches into the floor for batteries in my chassis. The seating position will be similar to an exotic, but the overall height of the car will be comparable to a 300m. I'm designing the chassis to use the 300m as a donor including the gas engine, but with the ability to easily convert to electric when the time is right for the owner.

They do already have stage 2 and stage 3 fast chargers. A stage 2 will fully charge in 3-4 hours. The stage 3 will charge I believe up to 90% in 20-30 minutes. Also the "Better Place" concept of battery swapping stations could be a possiblitlity with Tesla recently demonstrating a 90 second full pack swap in one of their test cars. The average stop in a gas station is 7 minutes.

I've been following the drama of Better Place and Shai Agassi and have decided to access my packs from underneath as well. This way, if there is a standard pack size that becomes available it will be easier for people that have my chassis to take advantage of it. It's wishful thinking for the future and the possibility of swap stations. Either way, it'll make it easier to pull the pack to work on it. This also leaves the possibilty of purchasing a small pack for your daily commute, then renting a large one for extended trips.

With a proper tube chassis in the 500-700lb range, and composite bodies in the few hundred pound range, there is room for a healthy pack size. The weight of the finished vehicle will be comparable to an everyday modern car. The important thing is for people to size their pack for what they ACTUALLY NEED on a daily basis. Not for the once or twice a year trip.

As far as hybrids go, I don't really see a point. It's like dragging around both your wife and mistress at the same time. You may think your getting the best of both worlds but what you'll end up with is two pissed off women trying to figure out how to take your money. Your mpg is never that great, and you still need to deal with replacing the pack one day. Extended range hybrids are a little better, but you lose range on a daily basis carrying around the gas engine that you may only need a few times a year.

[trukr]

I don’t have much knowledge on this subject but am very interested. Please keep the info coming.

That's exactly what I wanted to hear. As much as I like electric cars, all the images of converted geos, saturns, s10s and stock civics hurts my soul. The bugs I don't mind.

Some interest from kit car owners would be awesome. Feel free to throw out concerns and deal breakers. Maybe as a forum community we can figure a few out.

[LamboIllinois]

Have you heard about the battery prototype that a group at the University of Illinois made? The anode & cathode were built using nano-spheres which greatly increases the ability to move electrons. They were saying that hours of charge time would become minutes & minutes would become seconds.

trukr, where do I find the EV album? Regarding my EV setup, I don't have any specific design other than an AC motor & lithium batteries. I'm just absorbing ideas.

[dratts1]

I pretty much agree with you about hybrids. The 918 Porsche is something else though.

There are quite a few existing conversions already, but you are absolutely correct about the difficulties. The conversions have limited room for batteries and therefore suffer from limited range. 120 or so miles seems to be the upper limit, 60 to 70 seems to be the norm.

I've been factoring a good 6 to 8 inches into the floor for batteries in my chassis. The seating position will be similar to an exotic, but the overall height of the car will be comparable to a 300m. I'm designing the chassis to use the 300m as a donor including the gas engine, but with the ability to easily convert to electric when the time is right for the owner.

They do already have stage 2 and stage 3 fast chargers. A stage 2 will fully charge in 3-4 hours. The stage 3 will charge I believe up to 90% in 20-30 minutes. Also the "Better Place" concept of battery swapping stations could be a possiblitlity with Tesla recently demonstrating a 90 second full pack swap in one of their test cars. The average stop in a gas station is 7 minutes.

I've been following the drama of Better Place and Shai Agassi and have decided to access my packs from underneath as well. This way, if there is a standard pack size that becomes available it will be easier for people that have my chassis to take advantage of it. It's wishful thinking for the future and the possibility of swap stations. Either way, it'll make it easier to pull the pack to work on it. This also leaves the possibilty of purchasing a small pack for your daily commute, then renting a large one for extended trips.

With a proper tube chassis in the 500-700lb range, and composite bodies in the few hundred pound range, there is room for a healthy pack size. The weight of the finished vehicle will be comparable to an everyday modern car. The important thing is for people to size their pack for what they ACTUALLY NEED on a daily basis. Not for the once or twice a year trip.

As far as hybrids go, I don't really see a point. It's like dragging around both your wife and mistress at the same time. You may think your getting the best of both worlds but what you'll end up with is two pissed off women trying to figure out how to take your money. Your mpg is never that great, and you still need to deal with replacing the pack one day. Extended range hybrids are a little better, but you lose range on a daily basis carrying around the gas engine that you may only need a few times a year.

[mr. K]

well for starters, from the cursus i took ( okay, it was an indealer cursus, so everything is made to look better than it really is ) but its seriously performance enhancing. for short trips to get groceries or visiting grandma, its nice to drive all electric, quiet and relaxed, and no fuel burnt. for sportcars this will be different. yet even with this volvo v60 (the diesel engine already is a 215hp - 440nm engine ) but the electric engine boosts it to a total of 285hp - 640nm to 120kmh, after that it quits. but it will do 0-100kmh or 0-60mph in 6.0 seconds

[trukr]

There's no question about the performance benefits of a hybrid set up for performance. It's been done forever in trains.

I think for a hybrid or any type of EV to make financial sense, you would have to save enough money in fuel costs to replace the pack for free... at a minimum. Then you still have to worry about the maintanence, limited life span and associated costs for the gas engine and its support systems. This just goes back to the way cars are already. A never ending expense that constantly depreciates with a limited usable life span.

I do like the idea of a genset you can rent and add for long trips. The genset would run at a constant ideal rpm and only provide enough power to maintain hwy speed plus say 20%. All acceleration, inclines and headwinds would draw from the pack. Most cars only need about 25hp to maintain hwy speeds, add a little on top of that to slowly replenish your pack and cross country travel becomes worry free. The trick would be to get it small enough to not need a trailer to tow it, and removable so it doesn't become a burden when not needed.

I think this is when a twin motor build becomes ideal. Once freeway speeds are achieved one motor can switch from traction to generator. Then you wouldn't need a genset, but just a small engine instead.

[trukr]

Here's a link to a calculator for hp at a given speed.

Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com

[FUGAZZIDESIGN]

Trukr, you asked wich setup i was going with for the motors, we have decided on the porsche setup.