Dual Motor Electric Go Kart Does Laps At Newcastle Kart Racing Club’s Track During EV Prize
The Funky Car Skins-ElectricCarConversionBlog.com Dual Motor Electric Go Kart recently completed several laps at the Newcastle Kart Racing Club’s Track. The event was part of the Hunter Valley EV Festival 2013 EV Prize where the Dual Motor Electric Go Kart participated in the demonstration category. Just prior to the event, I was not sure if my kart was ready as I thought I had a faulty main relay and the kart had to meet various scrutineering standards. A bit of work was required so that I could drive those laps.
What Needed To Be Done Before Getting To The Track?
Due to various other things happening in my life and working on another motor for another Electric Go Kart Conversion, I had very limited time to prepare the Dual Motor Electric Go Kart to meet EV Prize standards. In fact, I had not driven it for around 3 months. The last time I took the kart for a drive, the main relay (for the traction circuit) kept cutting out. I thought it was faulty so it was replaced, only for the problem to repeat itself. After tracing through the problem, it turned out that the batteries I used for the control circuit would run out of charge (I was using two 9 volt batteries in series which seemed to work for short while).
New Battery For Control Circuit
For this event, a different battery was used for the control circuit which was a 12 volts, 7 Amp Hour Sealed Lead Acid battery. With the control circuit consuming under 2.5 amps, theoretically this battery would last 7/2.5=2.8 hours which is sufficient. So after all, the main relay was working fine and the root cause of the problem was the battery used.
Brackets had to be fabricated (with no sharp corners) to hold this battery in place which my neighbour made. The battery was installed just under the steering column on the floor of the kart and wires were routed to the battery.
Sharp corners removed
I removed all sharp corners (most were on the traction battery rack) from the kart.
The traction batteries were flooded lead acid car batteries, but the battery posts were different so the cables were changed to suit the battery posts.
As I ran out of time at home, the kart was packed into my transport vehicle on the Saturday night and driven to Newcastle as is. At the track, the officials/volunteers found a spot around the pit area. The kart failed scrutineering twice (which did not surprise me) and I was not sure if I would be able to do some laps around the track. The time allocated to do the demonstration laps was fast approaching and I did not have much time to rectify the issues. However, thanks to the support and assistance of spectators (in particular Rob and Tom) and officials, they finished off the necessary preparations for me. Things that needed attention were
- Replacing a rear hub.
- Changing a wheel so that the same axle had the same size wheels (previously, I had one big wheel and a small wheel which was great for going around right turns, but not good for left turns. This track had both left and right turns).
- Securing the traction batteries in place.
- Securing all cables and wires.
- Sorting out loose ends and bits.
Rob, who is an experienced kart racer briefed me about the track which was important for my mental preparation.
After it was scrutineered for the 3rd time, it passed. It was time to quickly get my helmet, Leatt brace and gloves on. One of the officials/volunteers assisted me with my Leatt brace and another assisted with pushing my kart from the pits to the track entry. Rob was filming on my behalf. Without those spectators and officials/volunteers, I would not have had a chance in getting my kart on the track.
What Was Driving On The Track Like?
I did not think that the batteries would last half a lap and asked if I could just do the half circuit. That was not possible as the link that completes the half circuit was blocked so I had to do the full track. This was the first time I was on this track and it was an amazing track. The first corner I took, I had to ease off on the power because the Dual Motor Electric Go Kart was starting to over steer and going into a drift. Through the various corners, I was trying to work out if I should take a racing line or an efficient line. I also opposite locked on a number of corners which was fun. There were other vehicles on the track and I caught up to one of them on my first lap. I was not sure if the driver in front was taking a racing line or an efficient line nor was I sure if the driver knew I was behind them so I waited a few turns before over taking it on the straight. (When I spoke to the other driver later in the day, he mentioned that he did not even hear me coming.)
Upon completing my first lap, I saw official’s hands waving to come in, so I started to come into the slip lane for the pits, thinking it was for me to come in, but it was for the other vehicle I just over took to come in. I was instructed to continue driving so I did and on my second lap, I was going over the ripple strips and taking the corners faster. I had got used to the oversteer. Also, my left thumb was getting tired from holding the button (the on/off switch which activates the main relay for the traction circuit) so on the straight sections, I used my right thumb. After completing the second lap, I was amazed that I was still going. I had driven for over 2km on modified electric stater motors that were not originally designed for use for over 10 seconds. As I went past the straights, there was no one to wave me in, so I went for it to start my 3rd lap. I had started to take quicker lines and I felt I was getting faster. However, I could also smell the motor windings and I thought this was not a good sign. I kept going for a few more turns and started climbing a hill when I could really smell the motor and the kart slowed down a bit. I decided to pull over and waited for the officials to come and help me bring my kart back to the pits. Upon returning to the pits, the ambulance ensured that I was OK and not dehydrated.
Upon reviewing the video footage Rob took, I think Rob mentioned that I should have pushed it [the kart] to the top [of the hill], get on it and go. (Now, I wish I had a two way radio.) I should have done that and when I think about it, after that hill, most of the track is down hill so I could have coasted back to the pits and complete 3 full laps.
According to my battery charger, the traction batteries had 25% charge remaining.
Setup of the Dual Motor Electric Go Kart When Doing Those Laps On The Track Control Circuit
- Push button switch which turns main relay (of traction circuit) on or off.
- 12V 7.5Ah SLA battery.
- Two 12v flooded lead acid car batteries (one was a Century DIN65L and the other was a Century 68) wired in series to deliver 24 volts.
- Two modified permanent magnet starter motors electrically wired in series with each other.
Doing a few laps at the Newcastle circuit demonstrated that I could push the modified starter motors beyond their original design limits. It was fun driving around the track and having the Dual Motor Electric Go Kart oversteer around corners and to drive over the ripple strips. The people in Newcastle are fantastic and they were keen and helpful in ensuring that I could drive on the track. I hope to be back next year with a better and faster Electric Go Kart and hope to deliver some excitement for them.
- Never give up. Although the kart was not ready (even when I got to the track) and it needed further preparations, I eventually pulled through with lots of help from many people.
- Keep going and push the limits. Part way through my 3 lap, I pulled over as I could smell the motor. I should have just pushed the kart to the top of that hill and then keep driving as the rest of the lap was mainly down hill.
- Listen to good advise. Having someone like Rob give me advise on the track and kart set up meant I could make informed and better choices with less mistakes.
- You can have fun on a budget. If you have followed my Electric Go Kart story you will notice that this kart has been built on a budget, yet I was still having fun.
I have many people to thank for giving me the opportunity to drive my kart around the track. The Hunter Valley EV Festival team (officials, volunteers, ambulance etc) really organized a great event. The event’s sponsors for their support and making this event possible. The crowd/spectators (especially Rob and Tom) for helping me with preparations, set up and advise as well as the officials/volunteers for helping me out and everyone involved with the event. There were also a lot of encouraging words from the crowd and others at the event which I appreciated. My neighbor for fabricating some parts for me the day before. Funky Car Skins for doing my graphics, Canberra EV members for parts and kart development opportunities and everyone who has helped me along the way.
This is Al Bunzel signing out.
P.S. Do you think I should put a motor controller on this kart and Lithium Iron Phosphate batteries on this Dual Motor Electric Go Kart or leave it as is and rather focus on the next Electric Go Kart? Please put your comments below.