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THE MOST INFORMATIVE WEB SITE FOR ELECTRIC VEHICLE CONVERSION |
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Frequently
Asked Questions and Answers
Not counting the cost of the donor vehicle, you will spend between $6500 and $9500. It depends on the type of vehicle you are converting, which determines the size motor, controller and number of batteries. The total cost also depends on how much metal work you can do yourself. See the Bill of Materials page for cost estimates for major components.
Lead-acid battery based EV conversions are limited to a maximum range of 50 miles in 60 to 90 degree weather using the maximum practical number of 'fresh' golf cart batteries that end up almost completely drained, which is very bad for the batteries. In other words, 50 miles is the maximum stretch limit. Most conversions have a range of 30 to 40 miles with the batteries ending up heavily discharged. An ideal daily range is 20 to 30 miles because it most likely will not over-discharge the batteries to excessively shorten their life.
There are many variables that determine range including size and weight of vehicle, number of batteries, capacity of batteries, age of batteries, air temperature, driving habits, terrain and the quality of your charger. If your daily range requirement is less than 30 miles, you should get reasonable service from your batteries, probably two years, maybe a little more.
I have found that my Chevy S10 pickup truck conversion, which has 16 six-volt golf cart batteries and weighs a total of 3700 pounds, had a maximum range of about 35 miles, 20+ miles at the 50% point. Keep in mind that driving habits impact distance. Also, as the batteries age, range decreases. After 1 1/2 years, my range is now between 25 and 30 miles max at nearly full discharge.
My converted Chevy S10 has a top speed of almost 60 mph using 16 batteries. Most people who convert a Chevy S10 use 20 batteries, have a top speed of near 80 mph and a range of about 40+ miles (not at 80 mph). I don’t have a need to drive on the freeway, so a top speed of 60 mph and a range of 35 miles are just fine for me.
A simple way to measure state
of charge is to measure the voltage of the battery bank a couple hours
after you have driven it – and before you start charging, of course.
The chart below is the one that I use to determine the percent
charge remaining. You can
make your own chart for the number of batteries you use.
The third column, Individual Bat. Voltage, is simply multiplied
by the number of batteries to create the first column. Many say
that measuring the specific gravity is the best way to determine charge
level, but who wants to mess with battery acid!
The
actual cost to charge your batteries depends on your overall design,
your charger and your driving habits. In my case, the cost per
mile ranged between 5 and 6 cents when the batteries were new and the
cost of electricity was 9.7 cents per kwhr. The cost per mile now, after
1 1/2 years is between 6 and 7 cents per mile. The cost of
electricity for me is now 12 cents per kwhr. I have devoted an entire page
to carefully answer this question. Click here!
The
6-V golf cart batteries are around 65 pounds each.
The 12-V deep cycle batteries are usually about 10 pounds more.
·
Use
a quality charger that has three charge phases: constant current,
constant voltage with decreasing current and a lower constant voltage
for the final phase. The
final charge phase is often called the finishing phase or the soak-in
phase. The charger should
also provide a manual equalization charge mode that you can use at wide
intervals to restore balance to your series connected batteries.
Equalization removes sulphate build-up on the plates and helps
restore performance. ·
Keep
the batteries charged. ·
Do
not routinely discharge the batteries down to 40% or less of remaining
capacity . ·
Check
water levels in the batteries at least once per month, especially during
hot weather. Only add water
after charging, not before. ·
Never
add acid to the batteries. · Inspect the battery terminals to ensure they are tight. A loose terminal connector has contact resistance that will create a large amount of power loss in the form of heat and even melt the lead terminal post down.
It's
beginning to look like 2 years for me, but it all depends. More.
. .
Assuming that your goal is to have the same voltage either way, you will have less capacity and range using the 12-V batteries. However, if the vehicle is small and light, 12-V batteries are the best option because of lack of space and the need for less weight. Many Geo Metro and VW Rabbit conversions use 12-V batteries. Realize that these are not 12-V automobile batteries. They are deep-cycle batteries intended for golf cart and other electric vehicle use. 8-V golf cart batteries are also available as a design option.
Lithium-ion (Li-ion) batteries are very expensive and they require an expensive charger and protection electronics for each battery. A company I investigated recently offers 12-V Li-ion batteries for vehicle applications at a cost of $2500 each plus another $500 each to cover the special electronics and charger. Compare one of these to two of my 6-V golf cart batteries at a cost of only $130.
#2 should be the smallest cable size that you use to interconnect the batteries, high-current fuse, circuit breaker, high-current contactor, current shunt, controller and motor. #4 and #6 are smaller diameter sizes that should not be used – too much power loss and heating. Visit your local welding supply store to obtain a flexible welding cable of size #2, #1 or larger. I used #2 and it is just fine for my application.
Terminal-post clamps are best because they offer more contact surface area to handle the high current and will stay tight. If you decide instead to use the wing-nut bolt on each terminal post, make sure you use the correct size cable terminal end, usually a 5/16” hole and that you use a spring-type lock washer under the wing nut. If you fail to use the lock washer, the wing nut will become loose, contact resistance will increase rapidly, heat will increase dramatically and the terminal post will melt – not pretty.
An
automatic transmission will use more energy than a manual transmission,
which means less range. I
have heard it done, but not very often.
This
is a very common question. If
a transmission is not used, a gear ratio that allows the motor to start
easily under load must be used. The idea behind this is to ensure
that the motor is not over burdened when moving the vehicle from a dead
stop. With such a starting and fixed gear ratio, the vehicle will
reach a top speed that corresponds to the top safe RPM of the motor.
For example, I can start off in 2nd gear and accelerate to about 30 mph.
If the ratio of my second gear is to be used for a fixed gear ratio, my
top speed will be about 30 mph. To get higher speeds, gear
shifting is needed.
Gear shifting allows for increased speed as the electric motor
stays within its rpm design range.
Most people install both an ammeter and a voltmeter. The ammeter helps you determine when to shift gears and how to optimize the use of the 'gas' pedal and conserve energy. The voltmeter is of little use at all because it will vary widely as you accelerate and coast. The voltmeter cannot tell you the true state of charge until the vehicle has rested for a couple hours. Unless it is a digital voltmeter, it won't be accurate enough anyway. So, an inexpensive multimeter can be used to measure your bank voltage until you are familiar with the discharge and range capabilities. If you have some extra money, you may be able to find a computing meter that keeps track of discharge and shows you what is left.
This
photo shows how I embedded the ammeter in the instrument cluster,
replacing the fuel gauge.
Yes. My Chevy S10 started at 3,040 pounds and ended up being 3700 pounds. The good news is that it is below the chassis and suspension ratings and the weight ended up being evenly distributed front and rear. I did add height-raising extensions (shackles) to the back of the leaf springs and a set of air shocks. The reason I did this is because the front of the vehicle was now lighter and caused the front to be higher than the rear. I wanted the rear to be slightly higher. For smaller vehicles, the suspension system will be challenged, especially with passengers. Add booster springs or shocks with coil springs.
My
experience thus far (see Evaluation), and the experience of
many others, says yes! Build
it well. Keep an eye on
battery water and terminal tightness.
Still an unknown to me is exactly how long my battery bank will
last until I am forced to replace it (see Battery
Service Life).
A few people have done so. However, you need access to a metal lathe and other precision tools. It is a difficult process that requires a precision outcome. Balance and alignment are critical. My advice is to buy these parts already precision manufactured and ready to bolt on.
I
discovered that the truck bed on my Chevy S10 weighed 320 pounds.
The truck weighed 3,040 pounds with the bed and 2,720 pounds with
the bed off. I made a
light-weight bed using 2” square aluminum stock, used for patios, and
ABS plastic sheathing (3/16” on the sides and ¼” on the bed floor).
That saved me a couple hundred pounds.
It allowed me to make a nice compartment with a lid to cover the
batteries. Some people make
simple flatbeds, add trailer lights and call it done.
I
have seen some truck conversions that place 8 batteries under the frame
behind the rear axle – that’s 500 pounds of weight behind the rear
axle. It not only places a
great strain on the rear springs, but it also adds a lot of outward
force when going around a corner – not good on wet or icy pavement.
Placing the batteries in a secure steel rack behind the cab and
resting on the frame yields an even balance of weight front and rear and
provides great handling.
Some
people do try to keep the air conditioning (airco).
They use a motor that has a shaft sticking out of both ends.
The front shaft interfaces with the flywheel and clutch assembly. The
shaft sticking out the back end is used to mechanically connect to the
airco compressor. Keep in
mind that if you do this, you will have no airco when the motor is
stopped, which as it turns out is a lot of the time during stops and
coasting. Also, the energy
needed for this airco comes from your battery bank, shortening your
range.
This is a very common question. The short answer is that the generator would have to be fairly large to constantly replace the energy that is being used. The gasoline engine on the generator would be large enough to run the vehicle directly without the generator or electric motor. That brings you back to a conventional vehicle.
The long answer involves some math. In round numbers, let's say it takes 16 kWhrs of energy to replace what is used from the batteries over a 1 hr period (average speed of around 35 mph). It means that a 16 kW+ generator must be used over that 1 hr period to replenish the used energy. At 100% efficiency, it takes 1 horsepower (hp) to create 746 watts (W) of electricity. In reality, the conversion process is not 100% efficient, meaning that it is more like 1 hp can create only 634 W (0.634 kW), a safe estimate at 85% efficiency. Now, we divide 16 kW by 0.634 kW and we get 25.2. That means we need a 25.2 hp gasoline engine to drive the generator to produce 16 kW of electrical power. Over the 1 hr period of operation, that's 16 kWhrs of electrical energy.
The advantage of such a system is that you have a limitless range of travel, like a conventional vehicle, as long as you don't exceed an average speed of 35 mph or run into other circumstances that would increase the battery drain beyond what the generator can replace. If you plan on driving at a higher average speed, the kWhr energy usage will be higher and a larger generator and engine will be needed.
The disadvantages include the extra weight, system complexity, noise, increased maintenance and being once again tied to gas pumps and prices.
This is a very common question, but it requires a detailed answer - click here. |
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