Aussie EV Autocross Special

OK So I had my second event in this car today. I hadn't fixed the batteries yet so I wasn't expecting much. I was really treating it as another opportunity to test the car and identify anything else that needs to be modified. The event was a Khanacross (similar to an Autocross). The car performed almost exactly as I expected. It would launch fairly well (about 0.5 G) but then after the first 10 seconds I would struggle to get more than about 0.1G and sometimes I was only able to maintain current speed with no acceleration at all. You can see I was forced to over compensate in the corners in an attempt to maintain speed. But my suspension needs work as its not turning in very well. The car was far from the slowest on the day and showed a tonne of potential. Even just fixing the batteries (without altering the suspension) would probably have put me up amongst the front runners.

Really I have three things to change:
1.Batteries - If I can achieve consistent acceleration throughout the course I will be awesome.
2.Camber - The right front is at 0 degrees will the left wheel is at about 3 degrees. I think matching them both at 3 degrees would be my best guess.
3.Ackerman angle - The chassis is about 10 inches shorter than the doner car where I sourced the hubs. So the angle of the front wheels when turning is far from correct. As I corner the outside wheel is trying to turn significantly more than the inside wheel. This means they fight against each other and the outside wheel scrubs and pushes resulting in severe understeer.

Here are a couple of videos from today:
[youtube]hlGXK6u4hDU[/youtube]
 
[youtube]F8C-HSnuYn0[/youtube]
[youtube]4ZpKkELHcjk[/youtube]
[youtube]-lry28gNfLk[/youtube]
[youtube]qqtAcHh0q5I[/youtube]
[youtube]j40CQkR_BNY[/youtube]
 
They do sound good but I need to start now as I only have 3 weekends left to fit and wire them.
Its looking like I will go with some second hand holden volt batteries. I will get a 7kwh pack that would give me about twice the usable capacity that I have now.
 
I am about half way towards having the new batteries installed.
Because the space already exists I am trying to show horn them in.
I have struck some trouble as I am about 40mm short in width. I have tried every combination I could think of and I seem to only have 2 options:
1. Mount the first battery to one side of the space, running length wise. Then mount the second battery 4 inches higher to clear the wider base (saving some width) but then angling the battery out so the outside edge is an inch lower (so the cage clears it).
2. Mount the first battery in the centre of the space, running length wise. Then run the second battery across the car above the first battery.

Option 1 is ugly as sin, but has a lower centre of gravity, will eventually be covered and remains below the level of the car's walls.
Option 2 is neater but raises the centre of gravity and would protrude about 8 inches above the walls of the car.

I have all but decided to run with option 1. I havealready made the frame for option 1. I just need to finish it off this weekend in time for my first serious event the following weekend.
I have also corrected the camber. Both sides are now a shade under 3 degrees. I am out of time for the ackerman angle. I will just have to live with it for this event.
 
You can see in the preceding photo how I have worked around the cooling issue.
I have taken some garden hose attachments. I have cut off the thread. I have then cut some aluminium to suit the shape of the cooling gallaries. I have drilled holes in the aluminium and sandwiched the hose fittings between two of the pieces of aluminium along with some silcon to seal it. I have then used more silicon to seal these flanges against the galleries and held in place with the threaded rods through the batteries.
 
As long as it fits... :lol: How is performance with the the volt packs? It should be waaaay better. :mrgreen:

-JD
 
No idea yet. I am restraining myself from testing it until I have the cooling hooked up. But even if it just maintains the initial acceleration provided by the old pack I would be very happy. So I am super confident it will be great. If anything I am a little worried the new pack won't have the same restriction on the current which could start overloading other components / fuses. But if that is the case I will dial back the current restriction setting on the controller.

In other words I estimate the current system peaks at around 200-250 amps and when it peaks the acceleration is near perfect. So if limit the controller to around 300 amps it should still accelerate just as good as before but will minimise any wheel spin (due to increased current) and will also protect the components / fuses. The wiring should handle 350 amps, the motor and controller can handle 400 amps. But I don't see any point pushign the boundaries when I am already getting excellent acceleration. I might change my tune if I am topping out and trying to get an edge on the competitiors. But I think that is more likely in the khanacross. The next one of those isn't until May 22.

I will have a short test by the end of this weekend but it won't be long enough to prove the overall performance. It will only prove that it is working to some degree. I fell into that trap with my tests with the previous batteries. I really won't know for sure until the next event where I can open it up fully in a controlled environment rather than a half baked spin in my yard.
 
So mate are you going to spill the beans on the cost of those batteries $$$$

You need some where to test like a trucking yard must be some where you can go after hours ???

Cheers Kiwi
 
$2800 australian. Thats for 7kwh at 150v. I still need the charger and bms. So I figure another $2000 on top of that.

I have a power transmission corridor behind my house but its grass so it doesn't stress the batteries like a true event. It is very very fun though.

Even if I had a test location I am out of time. I will be hard pressed to just finish the job by the end of this weekend. I'm not that stressed about the test. I am confident it will be fine on the day.
 
Yes they are Volt batteries.

No idea about the KMs. But they seem to be holding more than their peak voltage so to me that indicates they must not be all that old. I figure if I get 3 or more years from them I will be happy.

The best information I can find puts them at 15 - 20 C (I hope it is accurate). Ideally 9 C or above would be fine. Absolute minimum would be 7C. But this is the battery rating, I don't think it takes into account the terminals. Looking at the size of the terminals I doubt they could handle any more than about 450 amps before acting like a fuse.
 
galderdi said:
Yes they are Volt batteries.

No idea about the KMs. But they seem to be holding more than their peak voltage so to me that indicates they must not be all that old. I figure if I get 3 or more years from them I will be happy.

The best information I can find puts them at 15 - 20 C (I hope it is accurate). Ideally 9 C or above would be fine. Absolute minimum would be 7C. But this is the battery rating, I don't think it takes into account the terminals. Looking at the size of the terminals I doubt they could handle any more than about 450 amps before acting like a fuse.
Click to expand...


Will be interesting to see how they perform mate :|

Where are you competing and when?

I have to come up to QLD for job after Easter would be great to see :D


Cheers Kiwi
 
March 19/20 Motorkhana in Rockhampton
April 24 Motorkhana at Willowbank
May 22 Khanacross at Willowbank
Aug 7 Motorkhana at Willowbank
Sep 4 Motorkhana at Willowbank
Nov 6 Khanacross at Willowbank
Nov 27 Motorkhana at Willowbank

Of course this assumed I don't break the car or myself in the mean time :shock:
 
Sure do. I'll have to work out the best way to get them on to the forum. It might be easier on monday as I already have them resized at work.
 
Well I am very annoyed. The supplier I had been dealing with has gone on an overseas holiday. He should have mentioned this to me. I have been dealing with him multiple times over the past few weeks and he knew my deadline. Now I am probably going to head off on a 1500Km round trip to an event with no charger. I will probably only get through about 75% of the event. Its a very long way to go knowing I won't complete the event. Grrrrrrrrr!!!!! :evil:
 
Here is a link to the build photos:

http://s1044.photobucket.com/user/Greg_Alderding/library/
 
Right now I've lost all motivation to do anything with the car. I've had to call off the Rocky trip. And I wouldn't have it working for the next event either. So there goes my 2016 season.
 
galderdi said:
Right now I've lost all motivation to do anything with the car. I've had to call off the Rocky trip. And I wouldn't have it working for the next event either. So there goes my 2016 season.
Click to expand...

I don't know how things are in your part of the world, but Power Supplies are pretty easy to come by around here... For the past decade I've used Vicor Megapack power supplies to charge most of my EV's - with (3) 48v/4.2a cards In one, each card adjustable from 30v-70v, I can charge a pack anywhere from 30v to 210v. Or you could get a smaller PSU/charger and charge your pack In sections, and the 40ah you can pull from your new pack at 80% DOD will last much longer than the 7ah you could pull from your old pack with a 50% DOD. Don't get hung up on needing a specific charger.

-JD
 
Thanks. I have no choice but to keep looking. But its really screwed my season because I am now out of time until late april.
 
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