The controller for my Car is the Soliton Jr.


When I was arranging to buy my car the original owner had a new 800 amp Kelly controller that was part of the deal. When he hooked it up so I wouldn’t have to, it didn’t last 3 minutes.  It was probably a rare defect for them, but I was out a controller. The owner reduced the price of the car again, since I had decided not to take his batteries. I then had to decide what controller I would use. During my research into various controllers I noticed that the warranty period on these things were about a month. I found it strange that for a device as expensive as a controller the warranty would be so short. I’ve concluded that many controllers must die very early in their lives because of operator error. I figured that manufactures were probably hoping you couldn’t even hook it up in a month, and they’d be off the hook if you killed it on the first attempt to drive your car. I’m not trying to offend any controller manufactures with the above thoughts. I can’t image making a device that hooks to a battery system capable of delivering 1000’s of amps, and selling it to the general public. This goes for about anything in an electric car. Anyway, this got me thinking that I wanted a controller with a reputation for being designed to last. If I was going to spend that much money I didn’t want to have to do it again in a couple of years. I ended up choosing the Soliton because it looks like one big heat sink, and when you read the manual you get a feeling the designers weren’t fooling around. They make it very clear what the controller can deliver for power, and for how long. Since this is my first EV conversion, I can’t really comment on the other controllers out on the market, and I’m not trying make it seem that other controllers aren’t as good or as robust. I have no way of knowing that.

Soliton Jr. In my car

The Soliton Jr has many programmable settings, and it is easy to program because you talk to it through a browser. You just hook up an Ethernet cable and type in it’s IP address, and your talking to it. It has 3 inputs that you can connect to things like the BMS, or the motor over temp switch. These can be set to work on either high or low logic inputs, and while they are designed to work at 5 volt logic levels they can handle over 12 volts of signal if you choose. I have one input connected to my motor over temp switch that goes open if it is too hot. I can the set the controller to limit the current when this condition exists. I have my low battery-warning signal from the BMS going to the other input. The controller will limit the current to just enough to get me off the road when this signal goes on. I can calibrate my accelerator range, and then program the controller so half throttle can be set to something higher. For me, I have it set to something like 75% throttle at half throttle. This makes the car behave more like my gas midget. After about half throttle, the torque doesn’t increase that much. So I’m used to only depressing the accelerator about half way. When I drove the electric Midget it was hard for me to get used to having to floor it to get 500 amps, so I changed it to deliver higher amps at half throttle. You can also set a slew-rate limit for the accelerator so if you do floor it, the controller will take some time before it delivers 500 amps. I used this at first, but now have it set to a fairly high level because I’m used to the way the car drives now.

I have a tach input from the motor to the controller, and I use one of the 3 programmable outputs of the controller to create the tach signal for my dash tachometer. The controller has an RPM limit feature, which is needed with my Warp 9 Impulse motor. It is very easy to over rev this in 1st and second gear.

When it came to mounting the controller, I had only one location it would fit after I placed my batteries. It barely fit over the passenger foot well. This caused 2 problems. The first was it made it hard to access the many wire connections that are needed. To get around this I bought male spade adapters to fit on the factory screw clamps. This made it so I could connect and disconnect wires without having to use a screwdriver. The second problem was that while the controller fit in this location, the hood was very close to the fans that provide the cooling for the controller. I found the controller was flashing it’s high temperature warning light at me on my very first drives. The controller will start to reduce the current it will supply as it’s temperature increases. This is a great safety feature, and will add to the life of the controller. I didn’t have many options for increasing the airflow to the controller, but this controller can accept water-cooling. Originally I was hoping not to do this, but I was sure glad it had the option. I added a CPU water-cooling pump, and radiator, and that stopped the over heating issue.

When I start from a dead stop, the acceleration is perfectly smooth, no jerks, no hesitation. It seems that other people talk about that problem, but I’ve never had that happen. It also comes with a simple, but effective logging program. I use the log files to measure my cars energy use. I just drive at a constant speed while logging, and then dump the file and I can compute Wh/m for that portion of the log. I’ve written them emails for advice about the cooling, and I got a reply within hours of my asking the question. It happened a couple of times, so I can attest to their quality of support.

Overall, the controller isn’t cheap, but because of everything I mentioned above, I highly recommend this controller. For me, it was pretty close to bolt it in and drive your car away.