Luigi

söndag 27 maj 2012

Test Drive

Hi all!

It's alive! I've been out on two small runs, only about 60km/h and it sounds and looks good. More data will be posted.

Here is a video showing the car in action:

tisdag 3 april 2012

I wanted to get the batteries as evenly distributed in the car as possible. In fact it turned out that I didn’t have much of a choice when it comes to battery installation. I had one rule, NO BATTERIES IN THE BACK SEAT! So that leaves me with the rear engines compartment and the small space under the front hood.

4*90Ah

2*90Ah

Four batteries are to be placed in the back of the car, two on each side of the Agni. The other two are to be fitted just behind the front of the car, where the original 12v battery was located.

In order to support the 60kg's of batteries in the rear I had to design a support beam that also would act as a rear motor/gearbox support. I decided to make it out of aluminum since it is light and it doesn't rust. This also gave me a splendid opportunity to learn how to TIG-weld.

After hours of puddle control practice and 20 liters of Argon I started with the battery frames. These are made in 3mm L-profile aluminum and the will hold the two pairs of batteries togheter.

The two frames had to rest on something and after consulting a friend I came up with a design that consists of a support beam made of 6mm U-profile aluminum that stretches from side to side in the engine compartment.

Rear support beam

The support beam is fastened on both sides of the engine compartment and also has an "arm" that connects to the original motor mount found on the fiat.

The battery frames fits tightly into the frames welded to the support beam and pack straps will be used to keep them from moving up and down.

This is the finished support beam with batteries mounted.

The battery frames and the support beam have a total weight of about four kilos.

Batteries - the achilles heel of your ev-project

What type of batteries should I use? That's a question that everyone involved in the EV-game needs to decide on. It basically all comes down to four things:

   · Type of EV

   · Planned usage/range

   · Budget

   · Complexity

Type of EV

If you are converting a boat with a displacement hull you can easily go for lead-acid batteries since that type of boat will normally perform better in the water with large ballast.

I use 100kg of lead-acid in my "double ender" and that works just fine.

Linnéa - equipped with a hybrid powertrain and lead-acid batteries.

On the other hand, if you are converting a motor cycle or bicycle you would not want the extra weight from Pb's and installation space is limited.

Planned usage/range

What is the intended use of the EV, proof of concept, daily commuter or race car? What your desired range 10, 100 or 1000km? All of these things come into count here. There are a couple of calculators available that can help you get an idea of how much power you need to do the job.

Budget

A fat budget makes all the difference. If money is not the issue you can buy top of the line cells from Kokam or A123. These cells can deliver enormous amounts of current and are made of the purest materials. We will go deeper into battery technologies later in the blog.

Complexity

4 lead-acid batteries in series and a 48volt charger, that’s pretty simple compared to a 26 cell Lifepo4 pack with BMS.

Since this blog is about the conversion of a car I guess that it falls somewere in between the two extreems. I could use six lead-acid batteries in the fiat, it has been done before, but it is not optimal. The plan with my conversion is to create a daily commuter that has a minimum range of 50 km.

My Solution

In order to keep the cost and the complexity on a human level I have decided to go with six 12 volt, 90Ah LiFeYPo4 batteries. Now these "blocks" are made up of four 90Ah cells that share the same characteristics.

15Kg 12v 90Ah

The producer claims that these four cells, if not abused, are so stable that the need for individual, per cell BMS, is nonexistent. Now I know you might think that is sound too good to be true, well I'm here to find that out for you.

I will use a simple kind of BMS but its one board per block, i.e. six boards. These "AKUMON" boards will monitor each block and will issue a 12v signal if the charge voltage exceeds 17 volts or if the battery voltage goes below 10 volts. There is also a bleed-function that will limit the current in the last stage of the charge.

The AKUMON board. Provides high and low voltage protection for LifeYPO4 blocks.

The charge to be used is a 3KW (Vmax 87,6 | Imax 32A) Lithium battery charger. The charger will have a relay connected on the power chord towars the 240v grid. If one of the AKUMON's detect a high voltage, > 17v, the relay will open and the charge will stop.

Batteries, charger and Akumon's where all purchased from www.ev-power.eu great service and good prices!

tisdag 13 december 2011

Choice off controller

In order to control the electric motor we need a controller. In its most basic form it interprets actions taken by the driver and adjusts the voltage and current to the motor accordingly. There are as many flavors of controllers as there are types of motors. A good source for finding motors and controllers that work together is www.evalbum.com.

When choosing controller you should, at least, consider the following.

· Make sure the controller matches your type of motor, DC, AC, series and so on.

· Make sure the controller can provide the amount of power you need for your application

· Make sure that the controller is easy to program and that there is some kind of support mechanism that can help you if you get stuck.

I've used the Controllers from Sevcon and Kelly and its two different worlds. First of all the Sevcon Gen4 controller is AC and the Kelly is DC.

Sevcon Gen4 G4845

. Apart from that the Sevcon controller is a state of art controller with more settings than you can ever imagine. On the down side the complexity makes is very hard to program and even if you are a dealer it can be hard to get support from Sevcon. On top of that the programming interface for the Sevcon Gen4 controller costs about $900!!!

The IXXAT 1.01.0087.10200 used for programming the gen4.

Kelly on the other hand uses a USB-to-rs232 cable that you can find in any computer store to program their equipment. Kelly's downside is, if you should believe the word on the internet, their quality. I've never heard so many bad words being said about any controller/manufacturer. I didn’t really choose Kelly, it came with the motor. But I will give them an honest try. I've already started by contacting support and they answer back in a day or two.

The problem I'm facing is that the red led on the controller is on all the time. According to the manual this means that is broken but it seems to be working quite ok. I've put together a document with pictures of the controller and schematics showing how it is connected. It has all been sent to Kelly for review. Programming of the controller is done via a GUI that runs on Windows. In order to communicate with the you need the USB-to-rs232 interface. According to Kelly all external devices, such as motor, throttle should be disconnected during programming of the controller. You don’t actually need the batteries connected as you can supply the controller with a minimum of 18 volts via J1. J1 is one of the two round connectors on the front of the controller. I hooked up a PC-supply to pin 1 (+) and pin 13 (-).

Apply power and connect the db9 connector to the controller. Make sure that you have already installed drivers for the USB-to-rs232 in windows.

The controller should, when booting up, turn on the green and the red led, after a few seconds the red one should turn off.

Start the programming software, you can get it from http://kellycontroller.com/support.php make sure you pick the right software for your controller.

I should mention that this is work-in-progress and all of the settings described here might not be 100% accurate. In other words, don’t blame me if something goes wrong. ALWAYS keep your car jacked up during testing.

This is the first window that pops up after starting the application. I'm going for a basic configuration using a 0-5v throttle as the only external device. The throttle gets 5v from the controller and by moving the lever it returns 0.9-4.10 volts to the controller. The controller also includes a micro switch but we will get to that later.

First of all I specified the throttle effective starting position to 1.2 volts. This means that that the controller won't send anything to the motor if the value from the throttle is under 1.2volts. I l left the throttle effective area end position at 4 volts.

Maximum motor current specifies the maximum current that will be sent to the motor. The value is a precentage of the total current handled by the controller. The 72601 can handle 600 Amps and the Agni has a maximum apm of 300, hence the 50% setting.

! Make sure your battery pack can supply the current specified !

On the second page we will set over and under voltage. These setting are important and will protect your battery pack. These values vary depending on the battery technology used. Get the right setting from your battery supplier.

Another setting on page two is control mode this is how your controller should behave during acceleration. I've always been told to use torque and not speed. Kelly introduces balanced and I'm guessing I will play around with these values later.

Throttle up/down rate determines how fast the controller should respond to the throttle signal

This is cool stuff, regen, regeneration of energy. Imagine that you are out driving and you run up on a red light. In order to stop you depress the brake pedal. A "normal" car does not have any means of recovering the energy generated during this phase. All the energy that kept the car moving before you pressed the brake is turned into heat. The good thing with an electric motor is that it can be turned into a generator and if your controller supports it the energy from the moving car can be returned to the battery pack instead of going up in smoke. At least that’s the theory of it.

Regen can be controlled in more than one way on the Kelly. I'll start with the simplest setup. When you step of the gas pedal regen will start! This might not be the best solution because it might be wiser to let the car freewheel down a slope then to try and capture the energy generated.

So I found out that if you connect the micro switch in the throttle to the controller you can actually decide if you want to start regen or if you want to freewheel. It works like this:

When you want to use regen you step of the pedal, but not all the way. The trick is to keep the micro switch connected.

If you want to freewheel down a long slope you let the pedal go to its starting position, which means the micro switch will be disconnected. This will deactivate regen.

See http://youtu.be/fEPFgumcJDM for more info.

When you are done with the configuration, click Finish and power-cycle the controller.

onsdag 30 november 2011

Out with the old and in with the new!

Hi again! I've started to remove the I.C.E and it's components from the car. It's a pleasure to work with the car since everything is clean as a whistle. First of all I removed the I.C.E. This can easily be done without removing the gearbox. I tried to determine the weight if the I.C.E but the scale only ran to 50Kg, I'm guessing 55-60kg.

Clean soon to be green machine!

The gearbox is ready for its new motor. I will pick it up from my mechanic this Friday. I'm thinking about plugging the hole for the starter but then again it might be good to get some air in there. The clutch will handle a lot more power with the Agni. Peak torque is about 53 Nm.

This is the clutch disc I use its for 500R/126.

This is the surprise of the day! There is a voltage regulator mounted on the left side in the engine compartment. I won't be using it so I removed it today. As I held it in my hand I noticed the resemblance between it and the pedal throttle I bought from Kelly.

Voltage regulator used to monitor charging of the 12 volt battery

Pedal throttle 5v

It turns out the bolt pattern for the two are the same! So I mounted the new throttle where the voltage regulator was once mounted and then, since I don’t want to alter too much on the car, I will connect the original wire to an lever mounted on the new throttle. Ecellent!

Electric throttle mounted where the voltage regulator used to be.

It has finally arrived! Can't wait to get going. But now it's time to go for some salmon fishing! Have a nice weekend.

Time for a major milestone! The motor has been installed in the car and it has been tested, only with 12 volts, but it turns and the clutch works just fine. I've decided to mount the controller, main contactor and fuse above the motor. I cut out an aluminum plate that is held in place by vibration dampers. Since the Kelly controller is sensitive regarding temperature I will mount a fan or to on the controller.

The Agni in place!

35mm² cable capable of 72V 500A

Some more work done today. As I said earlier the controller from Kelly needs some help to cool down. I've cut out an aluminum plate and used thermal paste between the plate and the controller. Two 120mm fans has been mounted on the controller to aid the cooling. The main contactor has been installed as well as the fuse. A thick rubber mat is used to shield the plate from the hi-power wires connecting to the controller.

Two 120mm 12v fans for extra cooling

Fuse, contactor and controller

Not to bad!

In the picture above the throttle and the lever has been installed. The lever is connected to the original wire for the gas pedal.

tisdag 22 november 2011

Gearbox adapter

So I've started to work on the adapter that will allow for the Agni 95-r to be mounted on the gearbox. There are some tricky part that needs to be solved. The flywheel has been modified and it's now 15,5 mm thick and has a diameter of 208,80 mm. The diameter is limited by the size of the clutch.

Gearbox bolt pattern and shaft

There is a pilot bearing in the crankshaft for the shaft coming from the gearbox, shown in the picture above. This bearing needs to be added to the new flywheel hub on the electric motor shaft.

Crankshaft and pilot bearing

I tried to reuse the hub on the crankshaft, by sawing it off, but the crank is hollow and there was not enough material in the hub to fasten it on the shaft of the electric motor.

New hub, lighter flywheel now we need to design the adapter. The adapter must retain the measurement given earlier in the blog regarding distance between flywheel and gearbox, 99mm.

First we will add 15,1 mm thick aluminum plate that contains the bolts that measure up to the bolt pattern on the gear box.

On that plate we will bolt a "ring" of aluminum that will hold the motor at a correct distance from the gearbox.

Agni, hub, flywheel and ring

One thing that we don't want to forget is that we need to be able to attach and remove the hub from the shaft of the Agni. In order for this to work we need a small "service windows" in the ring. The hub will be locked by two bolts aligned with the keyway.