Restoration

As you all know I got a bit too cocky chasing Porsches on the highway and the Agni had a brush meltdown. The first thing I needed to do was to get a new brush holder and new brushes. As it turns out one of my friends from the diyelectriccar.com forum is the distributor of Agni in Europe, www.jozztek.com, Jozztek has a deep knowledge of the Agnis and a lot of racing experience as well. I could not reuse any of the old parts so I got the brush holder fitted with brushes. Jozztek matches all brushes so that the voltage drop/resistance is the same between brushes.

Meltdown brush holder

New brush holder from Jozztek with matched brushes

Next thing on the list was to restore the commutator. When the brushes melted there was a lot of arching going on and the surface of the commutator, where the brushes connect, had to be refurbished. In order to refurbish the commutator surface I needed a "grindstone". Luckily I found a company just outside of Stockholm that specializes in DC-motors. www.karma.se has a wide range of brushes and tools for restoring electrical motors.



Commutator before resurfacing

You need to spin the motor in order to resurface the commutator. The RPM of the motor should be around 500 when using the stone from www.karma.se. Jozztek shared his bright idea to use the old brush holder and two old brushes to drive the motor during grinding. Split the brush holder in half and attached two brushes, one negative and one positive.

The Agni gives you 71 rpm/V so if you connect is to a 12V battery it will spin at about 800 rpm. Cut the grind stone so that you can fit it to the commutator. Use a vacuum cleaner during the grinding to collect the dust. You don’t have to apply a lot of pressure to the stone and you will feel when is working. Change position of the stone often and keep it steady.

Stop the motor every now and then and inspect the result. Don’t overdo it!

The picture above shows the commutator after it's been resurfaced. Next on the list is too fit the new brush holder and adjust the timing of the brushes.

Fried!

Just to show you what happens when you push the Agni above its limits:

I need to replace both the brush holder and the brushes. I need to get my foot of the gas and the water cooling in place J

This is a picture showing the armature of the Agni. I might have to prep the surface before installing new brush holder and brushes.

Street legal!!!

After two years of hard work the car is now done! I got "him" street legal today.



Performance modifications

I ran into an interview with the designer of the Agni 95R, Cedric Lynch, on the net and I found an interesting part about water cooling the Agni in order to boost performance. Now I know I'm not ready yet but this is FUN!
Apparently one can run about 50% more power into the agni if these steps are followed:

"It is possible to cool an Agni motor with water spray. The best place to spray is on the inner part of the armature opposite to the side the brushes run on, and you need about 40 millilitres per minute which you get from a 1mm jet fed by gravity with a 250mm head. Turn the water off before stopping the motor, so that it does not remain wet when it is not in use."

This is what I'm looking at right now:

The tank is located 250mm above the spray nozzle. The cooling water is controlled by a solenoid, normally closed. The solenoid is in turn controlled by a bimetal thermal switch, normally open, that triggers at 80C.

It just might work!

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:

 

 

Battery Installation

Battery installation

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!