[Greasemonkey84]

Hello fellow gearheads and tinkerers.
My name is Ronnie, and i am from the Netherlands (or Holland).
Thats one of those countries that uses the metric system, and so will i. So to make it more bearable i will be using a lot of calculators to convert from metric to US en vice versa.
I will do my very best when it comes to the grammar, but if i make a mistake please feel free to correct it so i can learn from that as well.
I am a 26 year old male with an enormous curiosity for technology.
I went to school to become a car mechanic, and later on went into the construction equipment. Due to my interests in electric systems i found a job in electric chain-hoists and hydraulic lifts.

My mostly viewed TV station is discovery science, and that is where I first saw someone convert a gasoline burning Chevy camaro to fully electric. I think it was that reverend gadget guy. Ever since i saw that, i had so many questions about conversions that i went looking for info on the web. I stumbled upon this forum and read a few topics, but i still could not find my questions answered.

So far i found out that ICE stand for Internal Combustion Engine, and that the biggest factor in every conversion seems to be the budget. The bigger that is it seems, the more reach and speed you are likely to get.
I also found out that there are people who like the car to have a clutch, and some people don't.
Well i am someone who would build it with a clutch, because i believe it wil drive more natural, and will make gear changing easier.

Now a few questions:
1. Why do most systems have such high voltages? A lot of forcklifts use 48V while on this forum i have seen a lot 144V systems.

2. Can you use the standard gearbox in a such a way that u can increase your range? They told me the faster an electric motor needs to spin the more power it consumes, so if you can keep the PRM's low with a gearbox will the range than increase compared to a non shifting EV?

3. How do i calculate which motor i need? How many volts and KW for example.

4.And the last one for today: What kind of car is more suitible for conversion?
Is a light car with little room for battery packs better or a heavier stationwagon wich has about double the batterypack space?

 

[rillip3]

Now a few questions:
1. Why do most systems have such high voltages? A lot of forcklifts use 48V while on this forum i have seen a lot 144V systems.

2. Can you use the standard gearbox in a such a way that u can increase your range? They told me the faster an electric motor needs to spin the more power it consumes, so if you can keep the PRM's low with a gearbox will the range than increase compared to a non shifting EV?

3. How do i calculate which motor i need? How many volts and KW for example.

4.And the last one for today: What kind of car is more suitible for conversion?
Is a light car with little room for battery packs better or a heavier stationwagon wich has about double the batterypack space?

Hi, and welcome to the forum.

If you had to drive a forklift at 100+kph, you'd have a higher voltage forklift too. The amount of work it can do is given in watts. watts = volts x amps. If you do not increase the volts, you have to have a huge amount of amps to get your target work done. It's much easier to carry and generate high voltage than it is high amps.

Most people keep the standard gearbox. You will want to change the way you shift, however. You want to keep the RPMs in the 3000-5000 RPM range (dependent on your motor). Most people stay in second or third gear.

Calculating the wattage is largely based on your range. How far do you want it to go? How fast do you need to go? This will help us guide you better.

Finally, you want a car with a good difference in the GVWR and the curb weight. If it's a light car, you'll get better range in town (you lose mileage when acceleration with a heavy car).

 

[Woodsmith]

Hello, welcome to the forum.


1. Why do most systems have such high voltages? A lot of forklifts use 48V while on this forum i have seen a lot 144V systems.
If the voltage increases then the current decreses for the same power With lower current the cable sizes can be smaller. Also the I2R losses are reduced. In addition a series motor speed is related to teh voltage so a higher voltage will allow a higher motor rpm.

2. Can you use the standard gearbox in a such a way that u can increase your range? They told me the faster an electric motor needs to spin the more power it consumes, so if you can keep the PRM's low with a gearbox will the range than increase compared to a non shifting EV?
I believe it is the other way around. As a series motor spins faster the back emf produced opposes current flow so the motor is more efficient. However, it also produces less and less torque. The motor will run most efficiently if it is at the highests speed with just enough torque to push the vehicle along at the speed you want.
Running at very low rpm is not efficient at all.

3. How do i calculate which motor i need? How many volts and KW for example.Pass on this. Your average diy home converter makes do with whatever motor becomes available. Generally a 9" diameter motor will propel the average medium car.

4.And the last one for today: What kind of car is more suitible for conversion?
Is a light car with little room for battery packs better or a heavier stationwagon wich has about double the batterypack space?
That really depends on your motoring needs.
Smaller and lighter will require less energy, and so a smaller pack, to power it but that is no good if you have a family of four and a big dog and a boat on a trailer to move about.
Also if you only want to drive 5 miles at low speed then your vehicle can be bigger and heavier then one for driving long distance at high speed.
Best look at your needs first.

 

[meanderingthemaze]

Welcome!

Yes, I think it is best for you to describe your needs before trying to guess what is best for your scenario. Once the users of this forums know what you need, they can offer great input.

 

[Greasemonkey84]

My wife's parents live 135 KM away. This about 1,5 hours of traveling for us.
If i build an EV, i want to be able to make that trip with an average speed of 100 km/h. We almost always spend at least 1 night there so charging before returning home is no problem.

So converted from metric to US: i want to be able to make a 90 mile trip with an average speed of 63 miles an hour without cutting it close, and stil have room for luggage for my wife and son and me, and the spare tire.
Regenerative breaking isn't all that beneficial for trips like that, since it's an hour at the same speed, and i hardly need to brake if trafic is not jammed.
Dutch traffic law demands that every vehicle that wants to travel on the interstate is capable of reaching a minimal of 60 miles per hour in speed, so that is my minimum as well.

As a donor car i would most likely use my curent car. A mazda 626 2.0i stationwagon fro 1996. Long engine compartment, big trunk, and weighs about 2600 pound (1200 KG) as it is now.

If we had money for 2 cars i would just take a suzuki swift or something like that and give it a range of 30 miles, so i can commute to work and back and do some shopping.
Regardless of make and model, the car would go on a big diet before i start, and keep everything as light as possible without it becomming unsafe. I would even fabricate a bonnet from fiberglass myself if the gain is substancial enough.

Geez.... seeing it al summed up like that i think i am going to need a big budget, and high tech parts
At least i have ambition

 

[Woodsmith]

That requirement puts you in the lithium battery camp straight away. It isn't impossible just costly.

You may be better off converting a small local commuter car for your 30 mile range and saving the Mazda for the long range run and maybe convert that later when battery costs are more resonable.

I need a 70 mile range at 60-70mph for my commute and I am working on a lightweight reverse trike to keep the weight down to 350kg plus batteries and myself. It would be nice to keep he overall weight less then 500kg but I doubt that will happen (I blame the 'honey seat' supporters as it can't possibly have anything to do with wanting big wire wheels!)
However, I simply couldn't afford to buy the batteries for a heavier vehicle.

 

[Greasemonkey84]

That requirement puts you in the lithium battery camp straight away. It isn't impossible just costly.

You may be better off converting a small local commuter car for your 30 mile range and saving the Mazda for the long range run and maybe convert that later when battery costs are more resonable.

Yeah, that does put my wish of building my own EV a lot closer to reality than converting my mazda. Maybe a toyota starlet or a suzuki swift. Those weigh about half the weight of the mazda.

Wich brings up another question:
Most small cars have the gastank under the backseat i believe.
Can you install battery-packs under the backseat, or do they get to hot to place them there?

 

[Woodsmith]

The former gas tank position is good if there is enough space.
Don't forget access for monitoring or checks if required.
There is often space over the motor/transmission but you may want to place the controller there too.

Also when the radiator is removed and any other plumbing parts that opens out the potential too.

Easiest thing is to have a look in the garage for your chosen car and see where others have put the batteries and other bits.

 

[meanderingthemaze]

When finding a location for your batteries, keep in mind accessibility and airflow. You should be able to solve heat issues with fans if done properly, but ideally, you would have a natural air flow to keep things simple. Lithium ion are supposed to be maintenance free in theory, but in reality, you are going to want to be able to access the batteries if something should arise.

I agree with Woodsmith about the range issue. If people could get 90 miles at 60mph easily, I think EVs would already be a lot more popular.

 

[Greasemonkey84]

They would be mor popular for sure. But with the gasoline prices here, i wonder why. Because we have to pay 1,52 euros per litre.
Now 1 galon is about 4,5 L wich means that here in NL we pay about 6,80 euro per galon of gasoline in some gasstations. But if you don't fuel up on the interstate it can save about 0,05 euro per litre wich is about 22 cent for each galon of fuel because the locations are cheaper and smaller. One would think that with these criminally insane prices EV's would be more popular anyway, but no. Most dutch people think they are not handy enough to build an EV themselves or are just too lazy. And if you want to buy 1 straight of the shelves, you have to pay way to much.
I.E.:a volkswagen golf varriant EV kosts you 70.000 euro's to convert!
Even Plugin hybrids aren't popular here. Extra fact of the matter is that a lot of people (like me) have no personal driveway. We either rent/buy a garagebox or park on public parkingstrips. If i ever buy a house i want at least my own driveway, preferably with a garage.

 

[meanderingthemaze]

Well, you're not alone. In the US, we too have the same types of attitudes and lack of infrastructure for charging at homes that don't have driveways, or apartment buildings.

It takes time, but it also takes us bugging people about it to keep it in the forefront of their minds.

 

[Greasemonkey84]

Today me and my brother were chatting about electric cars and how to build them. All of a sudden he asks:"If you take a 4 wheel driven car and keep the ICE mounted on the front axle, is it than posible to mount an electric motor to the rear axle at the diff and sepparate the front and rear so you have a homemade plugin-hybrid?
I thought that was a pretty good question. What do you guys think: Can a system like that be done, or is it too difficult or expensive to combine both systems?
Here in Holland you can buy a secondhand hybrid prius for about 7500,- euro's, so it might be more interesting to just buy one and give it a charger. But i'm simply curious if it's possible to make one myself.

It has become clear allready that i'm better of building a small EV that can take me to work and back with some juice left in the packs.
I just discovered a detour that has no highway so the 60 mile limit wouldn't be so important, but would be a nice bonus.
So that would make my plan as follows:
-Find a small car of a model that is commonly found on scrapyards for cheap parts, between 700 and 900 KG (1500 -1900 pound roughly).
-my commute to work is 25 miles, so if my range would be 35 to 40 mile per charge i would be safe for a 2-way trip, and i could still do my shopping with it.
-With my new route to work the top speed only needs to be 50 but 60 would be nice.
-Since it's only for commute and shopping, it would be possible to lose the backseat and put a bat box there if that doesn't mess up the weightdistribution to much.

All i need to know now for the preparations is how many volts does my system need to be, and how many batteries do i need for a 35 to 40 mile range at a speed of 53 miles per hour for a 15000-19000 pound car?

 

[rillip3]

Today me and my brother were chatting about electric cars and how to build them. All of a sudden he asks:"If you take a 4 wheel driven car and keep the ICE mounted on the front axle, is it than posible to mount an electric motor to the rear axle at the diff and sepparate the front and rear so you have a homemade plugin-hybrid?
I thought that was a pretty good question. What do you guys think: Can a system like that be done, or is it too difficult or expensive to combine both systems?...

In short, no. Long answer:

Yes, you can do this. However, you'll probably have to upgrade the suspension to take more load, as you're no longer remove the ICE, and adding several hundred pounds of batteries, electric motor, controller, etc. There is also considerable engineering to be done to make sure the motor isn't over-spun while the ICE is on (if you're doing power assist, like the Prius) or to switch over to the ICE when the pack is depleted (ala the Chevy Volt).

The amount of engineering/mechanics/electronics required is beyond your average enthusiast DIYer. But it is completely possible.

EDIT:

I missed the fun part of your post, MATH BITS!!

Assuming 250 wh/mi (300 is standard but you're talking about a < 2000 lb car), at 40 miles you'll need 10,000 wh. If you're going to use Flooded Lead Acid batteries (cheap) you'll need 10,000 x 1.5 (add 50% for Peukert) x 1.2 (keep 20% in reserve for a safe depth of discharge) so you get 18 kwh. The voltage is not really important, technically. You can get this energy with 12v, or 10,000v. But to keep the current needed down, it's best to go somewhere in the 100-200 range. 120v is a very common input voltage for a DC motor, so let's work with that. 18,000 / 120 = 150 Ah batteries, very doable.

If you get AGM or Lithium batteries instead, you can do better because Peukert is lower. Cost is the main factor against both. AGM gives better performance, but will likely have fewer life cycles than FLA. Lithium has more life cycles and performance than FLA, but costs much more, and BMS is usually needed as well. Lithium is its own can of worms you'll have to research more about, but AGM would look like this:

10,000 x 1.2 x 1.2 = 14,400 wh. 14,400 / 120 = 120 Ah batteries.

As you can see, if you increase the voltage, you can decrease the Ah needed. Your controller and motor will determine what voltage you can use. The upper limit on most motors is 120, but some can go to 144, 156 or more. If you go much higher, like 300, you're looking at AC instead of DC.

If you go with PbA batteries, you'll need ten 12v batteries for 120v. Or twenty 6v batteries, if you prefer. Battery selection will depend on price, personal preference, space, and other factors you'll want to research more. Most people now use 12v because of price and availability.

 

[Greasemonkey84]

seem doable.
And if i take 20 12V batteries of 150 Ah and make 2 strings of 120 volts in parralel, will that give 2x150=300 Ah?
There are also some terms i don't understand:
What is FLA -> Flooded Lead Acid?
What is AGM?
What is BMS?
What is peukert?
And where can i find those math bits to do some calculating myself?

 

[rillip3]

seem doable.
And if i take 20 12V batteries of 150 Ah and make 2 strings of 120 volts in parralel, will that give 2x150=300 Ah?
There are also some terms i don't understand:
What is FLA -> Flooded Lead Acid?
What is AGM?
What is BMS?
What is peukert?
And where can i find those math bits to do some calculating myself?

First place to check is the wiki:

http://www.diyelectriccar.com/forums/showthread.php?t=669&redir_from=668

Here's a quick rundown of the ones you asked about.

FLA = Flooded Lead Acid (PbA = lead acid, more generic, encompasses FLA, AGM, Gel, other types)
AGM = absorbent glass mat. Instead of having liquid electrolyte in them like FLA, it's in a glass mesh of sorts. This prevents it from being spilled and some other effects as well.
Peukert is an effect that reduces the usable energy of batteries. When you see a 120 Ah battery, that's a 20 hour rating. That means it can deliver six amps for 20 hours. It cannot, however, deliver 20 amps for 6 hours. The faster you take the energy out, the more internal resistance you encounter. That is the peukert effect. As you decrease the amount of time you spend taking energy out, you increase the amount of energy that goes to losses in the form of heat, instead of electricity.
BMS = battery management system. Typically only required for Lithium batteries, it monitors the voltage of each battery and helps ensure that one cell is not being overly drained. Lithium cells are not as fault-tolerant as lead-acid batteries and need to be babied a little more with some form of monitoring and balance. Some people will argue it is not strictly needed, however, it is generally considered best practice for Lithium, and unnecessary for PbA.

As for the parallel string, yes you can do that. However, a 120 Ah battery is going to weigh somewhere around 90 lbs. I don't think you want to try to shove 20 of them in the car. In general, you're better off getting a bigger Ah battery than putting them in parallel. For example, a 150 Ah AGM battery weighs about 100 lbs. (45.5kg). A 75 Ah AGM battery weighs 58.5 lbs. Two 75 Ah batteries in parallel have the same voltage, but weight 17 lbs (~8kg) more than the 150 Ah battery.

 

[meanderingthemaze]

I would also suggest that you take a read through the wiki. It covers the basics and will make your questions more specific which in turn will make the answers you get more useful.

Re 4x4 hybrid: I have no idea about 4x4 gearing, sorry.

Re Prius conversion: I'm no expert but from what I understand it is not a trivial task. It requires hacking the software (and voiding any warranty) and then understanding how to tweak it to get what you want. It's very doable, there are companies out there that will even sell you the conversion kit, but it's probably much easier to do a pure electric conversion to another car. Of course, if you're a software engineer, then maybe it's the other way around.

Best of luck

 

[Greasemonkey84]

Thank for the info guys.
I just genarlly checked the wiki, and i gues i have about a week of reading to do. If i remember everything the first time that is
The time to study is once agian upon me...

 

[Greasemonkey84]

I've read a lot the last couple of days, and started some calculations.
I picked a donor car , a 1992 suzuki swift that weighs 750 KG (1650 pounds) wich i would like to run on 120 or 144 Volts.

I found a short formula that stated you need 35W per KG or 35 kW per 1000 KG.
In that formula i calculated that i need about 27 KW for my motor.
That is all really great, but i still need to count the weight of the energy-pack.
I can not find a simple formula to estemate how many batteries i need, so calculating what motor i need i seems useless because the weight isn't right.

rillip3 did some explaining a few posts back, and said :
Assuming 250 wh/mi (300 is standard but you're talking about a < 2000 lb car), at 40 miles you'll need 10,000 wh. If you're going to use Flooded Lead Acid batteries (cheap) you'll need 10,000 x 1.5 (add 50% for Peukert) x 1.2 (keep 20% in reserve for a safe depth of discharge) so you get 18 kwh. The voltage is not really important, technically. You can get this energy with 12v, or 10,000v. But to keep the current needed down, it's best to go somewhere in the 100-200 range. 120v is a very common input voltage for a DC motor, so let's work with that. 18,000 / 120 = 150 Ah batteries, very doable.

I would probably go for 220 Ah batteries, and than 120/12=10 batteries would be enough for my commute. so if i figure out the weight of those, i can better calculate the power of the motor (and the rest).
Did i get that right?

 

[rillip3]

I've read a lot the last couple of days, and started some calculations.
I picked a donor car , a 1992 suzuki swift that weighs 750 KG (1650 pounds) wich i would like to run on 120 or 144 Volts.

I found a short formula that stated you need 35W per KG or 35 kW per 1000 KG.
In that formula i calculated that i need about 27 KW for my motor.
That is all really great, but i still need to count the weight of the energy-pack.
I can not find a simple formula to estemate how many batteries i need, so calculating what motor i need i seems useless because the weight isn't right.

rillip3 did some explaining a few posts back, and said :
Assuming 250 wh/mi (300 is standard but you're talking about a < 2000 lb car), at 40 miles you'll need 10,000 wh. If you're going to use Flooded Lead Acid batteries (cheap) you'll need 10,000 x 1.5 (add 50% for Peukert) x 1.2 (keep 20% in reserve for a safe depth of discharge) so you get 18 kwh. The voltage is not really important, technically. You can get this energy with 12v, or 10,000v. But to keep the current needed down, it's best to go somewhere in the 100-200 range. 120v is a very common input voltage for a DC motor, so let's work with that. 18,000 / 120 = 150 Ah batteries, very doable.

I would probably go for 220 Ah batteries, and than 120/12=10 batteries would be enough for my commute. so if i figure out the weight of those, i can better calculate the power of the motor (and the rest).
Did i get that right?

If you go with 120 v, then yes, you need 10 batteries. 220 Ah batteries are going to be pretty heavy. For AGM, I saw 168 lbs (77kg) per battery each; that's a total of 1,680 lbs or ~770kg. If you go with Flooded lead acid, it may go up or down; data on FLA batteries can be somewhat hard to find without having picked a specific battery manufacturer/model because they're not easily shipped and so not posted online much.

If you went with the 150 needed for the range estimate I did earlier, you'd be looking at 99 lbs/45kg each, which would be 990 lbs/450kg, a significant weight and cost reduction, but you'd have less range (about 33 miles less; 220-150 = 70 Ah. 70 ah x120 v / 250 wh/mi = 33.6mi or 54km.)

 

[Greasemonkey84]

I took a look on a few dutch battery supliers, and on one of them they made a attention point out of the outdoor temperature.
The last 3 years we have had -20 celcius a weeks strait.
When i still went to school they tought me that frost can affect a car battery.
After looking in to it, i found a site that stated cold can cut the range in half if it gets cold enough. So if i use 230 Ah batteries that should compensate for the range loss in the winter.

If i insulate the energy pack with rockwool or some kind of foam it will make the car heavier, but wil that have any positive effect on the winter temerature of the energy pack, or is that useless because the gained weight affects the range aswell?
And if so: does that then mean that an EV is far from ideal in the winter, or are there other systems that can make an EV winterproof?

Edit: i am corresponding with different supliers to recieve information on weight,capacity, cycle-life, charging currents , price, etcetera (hoping for discount)