Electric Vehicle Conversion Help - Frequently Asked Questions

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Frequently Asked Questions and Answers

How much will it cost me to do the conversion?

Not counting the cost of the donor vehicle, you will spend between $7000 and $11000. 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.

Which vehicles are the most commonly used for conversion?

Vehicles that are most often converted have a 4-cyl. engine and a manual transmission. Here is a list of the most common:

Chevy S10 pickups, Geo Metro

Dodge Colt, Shadow, Rampage

Daytona Ford Escort and Ranger

Porsche 914

Honda Civic

Mazda B2000 pickup

Datsun pickup

Plymouth Sundance

Pontiac Fiero

Suzuki Samurai, Sidekick

Toyota pickups

Volkswagen Beetle, Jeta, Golf, Rabit, Scirocco

What driving range can I expect on a charge?

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 found that when my Chevy S10 pickup truck conversion only had 16 six-volt golf cart batteries and weighed a total of 3700 pounds, I 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 was between 25 and 30 miles max at nearly full discharge. Now I have 24 six-volt batteries with a total weight of nearly 4200 lbs and a 50% DoD range of about 30 miles.

How fast will my converted vehicle go?

When I had only 16 six-volt batteries, my top speed was around 60 mph. Now, with 24 six-volt batteries, my top speed is unknown - I believe I could reach 100 mph, but will not try. 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.

How do I determine the charge state of the batteries?

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!

	State of Charge
Unloaded Bank Voltage (24 Batteries)	Unloaded Bank Voltage (16 Batteries)	% Charge	Individual Bat. Voltage	Spec. Gravity (80^o F)
152.88	101.90	100	6.37	1.277
151.44	100.96	90	6.31	1.258
150	100.00	80	6.25	1.238
148.56	99.04	70	6.19	1.217
146.88	97.92	60	6.12	1.195
145.2	96.80	50	6.05	1.172
143.52	95.68	40	5.98	1.148
141.84	94.56	30	5.91	1.124
139.92	93.28	20	5.83	1.098
138	92.00	10	5.75	1.073

How much does it cost to charge the batteries? What is the cost per mile?

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!

What can I do to keep the cost per mile as low as possible?

Use low rolling resistance tires and keep the tire pressure up.

Don't be a lead-foot. It's the same as a gas guzzler - take it easy.

Learn to coast a lot - you are traveling for free when you coast.

Use a high-efficiency charger so as not to waste energy while charging.

Plug into the neighbor's house instead of yours when charging. (I'm not serious.)

How much do batteries weigh?

The 6-V golf cart batteries are around 65 pounds each. The 12-V deep cycle batteries range between 45 and 75 pounds depending on AH capacity.

How should I care for the batteries to ensure long life?

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 sulfate 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.

More. . .

How long will the batteries last before they must be replaced?

2 to 4 years, but it all depends. More. . .

Why can’t I just use deep-cycle 12-V batteries to save space and weight?

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.

Why don't you use Lithium-ion batteries?

Lithium-ion (Li-ion) batteries are very expensive and they require an expensive charger and protection electronics for each battery. The price of lithium batteries is coming down, but still about 10 to 12 times the cost of lead-acid, including the charging hardware.

What size cabling should I use for the high-current connections?

#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.

For battery terminal connections, should I use the wing-nut bolt on the terminal post or should I use terminal-post clamps?

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.

Can I use an automatic transmission?

An automatic transmission will use more energy than a manual transmission, which means less range. I have heard it done, but not very often. Also, many automatic transmissions are computer-controlled based on feedback from the original Internal Combustion Engine (ICE).

Why do I need a transmission at all?

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 comfortably start off in 2nd gear and accelerate to about 35 mph (max.). If the ratio of my second gear is to be used for a fixed gear ratio, my top speed will be about 35 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. Also, electric motors provide acceleration torque in the low rpm range, which gear shifting accommodates.

What kind of meter(s) should I install so I can monitor as I drive?

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 analog voltmeter cannot tell you the true state of charge the same as a more accurate digital meter can. 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.

Having said that, a simple analog voltmeter will give you an 'indication' of state of charge and battery health by how far down the voltage dives during acceleration. As the batteries discharge and age, the voltage will dive more deeply during acceleration. The ammeter will indicate this by showing less and less current during acceleration.

This photo shows how I embedded the ammeter in the instrument cluster, replacing the fuel gauge. It's amazing what you can do with a hole saw!

After the conversion, will the vehicle be heavier?

Yes. My Chevy S10 started at 3,040 pounds and ended up being 3700 pounds with 16 six-volt golf-cart batteries. It is now about 4200 lbs with 24 batteries. The good news is that it is below the chassis, suspension and tire ratings and the weight ended up being evenly distributed front and rear (16 battteries). 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. I also predicted that I would need more clearance for the homemade bed. For smaller vehicles, the suspension system will be challenged, especially with passengers. Add booster springs or shocks with coil springs.

Are conversion vehicles really reliable?

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. (see Battery Service Life).

Can I make my own adapters, one for the motor shaft-to-clutch plate and one for the motor-to-transmission mount?

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.

Should I make a new bed for my truck like you did?

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, which of course is fine.

Why didn’t you put your batteries in multiple racks under the truck frame in front of and behind the rear axle?

I have seen some truck conversions that place 8 batteries under the frame in front of the rear axle and 8 batteries 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. The batteries and connections also stay clean.

Can I still have air conditioning?

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, unless you coast in gear. Also, the energy needed for this airco comes from your battery bank, shortening your range. If you have range to spare, this is not an issue.

Where can I purchase all of the components I will need?
See the Resources page. However, it is best to use Google and search for dealers.

Why don't you add a gasoline generator to keep the batteries charged all of the time?

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 almost 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. The advantage is that it enables you to take long trips.

Can I add a generator, or several generators, to my EV to keep the batteries charged?

This is a very common question, but it requires a detailed answer - click here.