|1. FocusEV Home||2. About Me||3. Decisions, Decisions||4. Acquiring the Parts||5. Removing the Engine||6. Mating the Motor|
|7. Battery Placement||8. Beefy Suspension||9. Wiring||10. Fuel Gauge||11. On the Road||12. Pictures of the Project|
|13. Tach and Speedo||14. Fuel Gauge||15. Power Steering Pump||16. Upgrade to Lithium|
FocusEV Frequently Asked Questions
I've received several questions from technical and non-technical folks. I'll try to answer them here. Keep in mind that I'm new to this so it's possible I'll get some details wrong.
Will your wife be willing to come pick you up in the middle of the night when you've driven too far and run out of "juice"?
Even though the range of an EV is limited more than a gas powered car, an EV doesn't run out as suddenly as an empty gas tank. In an EV the performance slowly degrades as the batteries drain down. (Think of a dim flashlight with weak batteries.) So from the instrumentation that I'll have in the car and by paying attention to performance I'll know when it's time to crawl back home or find an electrical outlet. Since outlets are pretty much everywhere in a city like Minneapolis I'll carry an extension cord for "opportunity charging". This means stopping at a business or home and asking for a few cents worth of electricity to get me back on the road. Other EVers tell me that they've never been turned down once they explained the electric vehicle concept.
An additional property of lead-acid batteries is that after partial discharge they gain back a limited amount of energy by letting them rest. So by sitting idle for a while they actually "grow Amps". And therefore Judy won't have to come get me in the middle of the night.
Will the FocusEV have a "gas gauge"?
For instrumentation I will initially install a 180-Volt Voltmeter and 500-Ampere Ammeter. These will provide a crude estimate of the energy I'm draining from the batteries and how much remains. I will need to learn how to estimate the state of discharge based on these instruments. But these instruments alone don't meet one of my criteria for the car - that anyone be able to operate it without special knowledge. Eventually I will design and build a computer-based energy meter that will display the remaining energy in the battery pack, the state of each individual battery, and the rate that energy is being drained. Once I've got the circuitry to monitor such things it will be interesting to figure out useful ways to display it. I'm planning a graphical vacuum fluorescent display mounted on the dash to present this information to the driver.
How does the cost per mile compare to a gasoline powered car?
This answer of course changes as the cost of gasoline goes up, but here's my estimate. To start, you need to know that electrical energy is measure in Watt-hours, or Wh. One Wh means using 1 Watt of power for exactly 1 hour. So a 100-Watt bulb burning for 1 hour uses 100 Wh. The utility measures energy in increments of 1,000 Wh, or 1 kilo-watt hour, or 1 kWh.
I'll assume that the car uses 300 Wh per mile. This should be achievable goal if I drive with energy conservation in mind. The electrical utility that feeds my home (Xcel Energy) charges me almost exactly 10 cents per kWh. If I drive 30 miles a day at an average energy of 300 Wh per mile then I'll use 9,000 Wh, or 9 kWh. The efficiency of the charger is less than 100%, and all of the energy that goes into the batteries doesn't get stored as usable electricity to eventually move the car - some of it goes into heat. If I assume that the efficiency of the charger and the battery heat losses add up to 80% (a number I cannot yet verify) then the amount of power that I need from Xcel Energy to move the car 30 miles is 11.25 kWh (9 kWh/80%). So the daily cost is 11.25 kWh x 10 cents = $1.12. This is the added cost on my electric bill per day. Therefore the cost per mile is $1.12 / 30 miles = 3.75 cents per mile. If I assume that the same car with a gasoline powered engine gets 25 miles per gallon, and that gas is $4.00 per gallon (it may very well be beyond that by the time you read this) then the cost per mile would be $4.00 / 25 miles = 16 cents per mile.
16 cents vs. 3.75 cents. So the gas car at $4.00 per gallon is more than 4 times as expensive per mile as the FocusEV.
Have you considered adding a generator to get some of the energy back to re-charge the batteries?
This question comes up a lot, but if you know anything about electrical generators you know that the energy required to spin them goes up as the amount of electricity generated goes up. And it takes a LOT of energy to spin the generator. So the bottom line is that it takes more energy out of the battery pack to turn the generator than the energy produced to put back into the battery pack. It will always be true that you cannot gain using this method, as explained below.
One of the laws of physics that can NEVER be broken is that energy is never created or destroyed - it is only converted from one form to another. All systems that convert energy strictly adhere to this law. The sun. A nuclear reactor. A solar cell. An internal combustion engine. An electrical generator.
And in virtually every process of energy conversion there is an inefficiency, or loss. This doesn't mean that energy is lost in the process, (since energy cannot be destroyed) but that it is converted to a form that you can't make use of. For example, in an internal combustion engine (ICE) you convert the energy in the gasoline (that originally came from the sun and went into the plant life that decomposed and turned to crude oil over millions of years) into rotational motion. But the ICE is VERY inefficient in that most of the energy from the gasoline is converted to heat. So the ICE converts the energy in the gasoline to heat (mostly) and rotation to move the car (less so.)
In our example of adding a generator, it takes energy out of the batteries to spin the generator. The energy to spin the generator takes away from the energy available to move the car down the road. And the resulting electricity that goes back into the pack from the generator is LESS than the energy it took away from moving the vehicle, since the generator also has losses (friction, even if small, converts some of the energy to heat.)
One of the keys to energy efficiency for the future of the human race is in using energy conversion processes which most efficiently convert to forms of energy that we can use. There are several energy ideas being pushed, like hydrogen fuel-cells (some call them fool-cells), and converting corn to ethanol. Unless the losses in these energy conversion processes are significantly impoved, they are simply not the answer in my humble opinion.
Why convert a Ford Focus?
See the explanation at the page called Decisions, Decisions I chose the 4-door sedan over a hatchback because the hatchback had too little space for batteries in the rear. I chose the sedan over the wagon because the wagon is heavier to begin with, which would reduce range slightly. I also want to keep the batteries separate from the passenger compartment, since the batteries can vent gasses that I don't want to breathe, and there's a slight risk of explosion. (Just as there's a slight risk of explosion of gasoline in all of our cars.)
How are the batteries wired up, series or parallel?
The batteries are connected in one series string. This will provide a pretty high voltage (high enough to be lethal) and has the same current flowing through all batteries to the motor controller. The motor controller steps down the voltage (and steps up the current) to the electric motor. The voltage delivered to the motor is controlled according to the position of the accelerator pedal (formerly known as the gas pedal.)
How much energy can the battery pack store compared to gasoline?
If I use a pack of seventeen 8-Volt Golf cart batteries, which are made for deep duty cycle use, I'll have a pack voltage of 136V. Each battery is capable of delivering a constant 56 Amperes for 117 minutes. (The car will draw higher current, which will reduce the actual time, but for purposes of calculating stored energy I'll use this number.) The theoretical stored energy in Watt-hours is 136V * 56A * 117 minutes / (60 minutes per hour) = 14,850 Wh, or 14.85 kWh. A gallon of gas contains about 36 kWh of stored energy, so the EV carries the stored energy contained in less than 1/2 gallon of gas. It should be apparent from this that Internal Combustion Engines waste a LOT of energy - mostly as heat.
How far will the EV go on a charge?
This is kind of unknown until the car is on the road and I can test and refine it, but I have used some calculators to estimate range. In an EV we can't use all of the energy in the batteries - discharging them completely will render them useless. So I will need to be careful not to use more than 50% to 60% of capacity. If assume that I can use 55% then my usable energy is about 0.55 * 14.85 KWh = 8.1 kWh. (See the stored energy above.) If I can make the car efficient enough to use an average of 300 Wh per mile, my range would be roughly 8.1 KWh/300Wh = 27 miles, give or take.
What can be done to increase range?
Decreasing drag is the thing that can help. This means making sure the tires are aligned, the tire pressure is kept up, and the transmission and brakes don't create excess drag. It also means driving slower since the drag due to wind resistance goes up as the square of speed. (The drag at 70 MPH is 4 times the drag at 35 MPH) I'm practicing my "hyper-miler" driving techniques to ensure I'm an efficient driver of the EV. (Coasting whenever possible, including up short hills, timing traffic light to roll through, limiting my acceleration from a stop, not exceeding the speed limit on freeways, etc.)
How much will the FocusEV weigh?
I had the car weighed on the day before I began disassembly at a local metal recycler. It weighed 2620 lbs. - 1620 lbs. on the front axle and 1000 lbs. on the rear axle. After removing the engine and associated cooling, fuel, and exhaust systems, then adding battery racks, the electrical controller and battery charger, wiring, and over 1000 lbs of batteries I expect that the car will weigh around 3,450 lbs. The car is rated at 3,630 lbs. (GVWR) which means that the structure, tires, brakes, etc. are designed to carry this much weight. Lots of EVs on the road exceed their GVWR but I want to avoid that situation. I will be installing heavier springs in the rear since that axle will go from 1000 lbs. to over 1,500 lbs.
Will the car be heated?
There are two areas that need to be heated; the batteries (most critical) and me. If the batteries aren't kept reasonably warm then they lose range in cold weather. Or in the worst case they are destroyed because they freeze when discharged. So I'll have foam insulation surrounding the batteries (isolated from the battery acid by fiberglass panels) and have heaters inside the battery boxes. (I refer to them as the BTIS boxes - Batteries Think It's Summer boxes.) The heaters will run on 110 VAC power from an outlet overnight while the car charges, and possibly at work on those really frigid days. As one EVer in a southern state wrote, those in the North coddle their batteries in cold weather with down blankets and sips of hot chocolate.
The interior will also have 110 VAC heaters that I'll run on some sort of timer so that the car warms up before I get in. (It should actually be a better situation than my current car which of course doesn't warm up for several miles.) I'll also have an on-board heater in the usual heater location, mainly to keep the windshield defrosted. That heater will run off the battery pack and will decrease the driving range somewhat.
Will the FocusEV have Air Conditioning?
Nope, AC takes too much power and would decrease my range. Plus it adds the complexity and weight of an auxiliary motor, the compressor, and the condenser. For the few hot days we have here in Minnesota I'll sweat it out. And I don't really mind the heat that much - I spent an entire summer in Austin, Texas driving a car without AC and it was just fine for me.
Will the car have regenerative braking (referred to as "regen")?
I started out with this on my criteria list, but then I started looking more closely at the cost and benefit. To get efficient regen I found that an AC motor and controller would be the best choice. This system is fairly efficient and is used by most companies that have built commercial EVs. This approach has the advantage of a sophisticated controller that is built for regen. But the cost of the motor and controller alone came to something like $6,000. This definitely didn't fit all of my other criteria. So I chose to go with a lower cost, simpler series-wound DC motor. (My brand-new motor and controller cost just under $3000.) Series-wound DC motors have been around forever and this approach appears to meet all of the other criteria for my EV. It also turns out that because most of my driving is in town and my speeds are relatively low, the amount of energy to be recovered with regen is not that great. And since regen doesn't provide 100% efficient recovery of energy the gain would not be that great for my situation.
And here's another FAQ on EVs
Updated 6MAY2008 CHS