Most of yesterday and the entire day today was full of rain. I wasn’t able to get much done compared to Saturday. Most of the day has been spent planning, researching, and cleaning the garage.
I’m working in a tight space with the motor controller, contactor, and motor. It’s difficult to bend thick cables, and harder to work with thick terminals overlapping each other.
I was in a tough spot with trying to get two wires connecting to the motor controller, and I was wondering if it was important that the wire from the motor goes to the controller, rather than directly to the contactor. Electrically, it didn’t seem to make much of a difference.
C-Car and one DIY EV conversion owner said their controllers were wired up in this way. I sent an email out out the manufacturer.
I have an SR-72500 Motor Controller.
I am installing this in a CitiCar, which was previously controlled by applying 3 different voltages to the motor.
I’m looking at the Generic Series /w SW202 Reverse wire schematic in the operators manual SR (page 22)
On all diagrams in the manual, I see:
1 wire going from the SW180 contactor to the motor controller B+ terminal
1 wire going from the motor controller B+ terminal to the series motor A1 terminal
I’m working in a tight space and it’s difficult to get two lugs onto the B+ terminal.
Can I have the wire to the motor come directly from the SW180 contactor? These are the changes I am proposing:
keep 1 wire going from the SW180 contactor to the motor controller B+ terminal (no change)
add 1 wire going from the SW180 contactor to the series motor A1 terminal
remove 1 wire going from the motor controller B+ terminal to the series motor A1 terminal
Technically speaking it will work, electrically speaking you’re going to cause an issue doing that. If this was a low current system, like a stereo then this would be fine, but since we’re low voltage high current we have to know where current is at all times. So when you put the two wire connection on the solenoid it turns the motor and controller into two separate loads the moment the solenoid closes and both are fighting to get the current coming out. Motor is bigger, it gets the current, and the controller just watches things happen without doing its job.
If you wire it that way, it will operate though, it may just do some weird things randomly.
I was taken back a bit. I half expected a basic answer of something along the lines of – only wire it the way we say to do it. This person went into detail of “WHY” with a simplified explanation. It’s exactly the answer I needed. I actually feel like I learned something.
I posted the manufacturers response on the Facebook post for the other C-Car owners to learn about as well.
Yesterday I was able to put some cables onto the motor, switches, and controller. I wired up the main contactor solenoid to the motor controller and a small switch as a safety measure to prevent the solenoid from being activated while working on it.
The main contactor was flipped to allow the cable to the controller to be made shorter. The suppression diode was too close to the metal mount for the SW202 switch, so I bent it into a new shape that actually made it a bit more ridged and let me get my hands down into the area much easier.
I also started to setup a couple relays to allow 12 volts to pass to either side of the SW202 switch based on if the car is going in forward or reverse. While I was at it, I started labeling the wires so it would be easier to figure out how to connect everything up once I started running wires from the dashboard.
Search for Parts
I found that out of 10 colors of automotive wire, I didn’t have pink. Pink is used to identify power for “reverse”. I went to a hardware, automotive, and farm supply store and couldn’t find the following:
- Pink automotive wire
- Relay with a 12v coil to pass 48v over the switch (actually, I couldn’t find any relays)
- Battery side wall terminal
I’ve never really looked around an automotive store in the past. Usually I order something online and go to pick it up. I was shocked at how little the store seemed to have.
Gutting Old Parts
I pulled out the 48 volt and 12 volt battery chargers. I started removing all of the loose wires inside the battery compartment under the seat. I’ve got three of the original wires unthreaded from most of the zip ties leading to the front of the car. I was starting to run into a difficult time in the front part of the car.
The vent from the motor to the flap has been removed. I need to determine how to heat and defrost the car now that the motor can not support it.
I placed all four lithium battery modules in the car and found that I had enough room to place the battery charger under the seat as well. I’m considering the best placement while considering where the J-1772 inlet can be installed.
The battery modules had little nubs on the side that prevented them from sitting flush against the car. I cut them off and they now sit flush, giving an extra quarter inch to the space available beside them. I also noticed that the two newer chargers are missing the black cable that connects to the battery charger. I’ve been thinking about mounting some small angle brackets to the bottom of the battery box to prevent the modules from moving around while driving.
I’m still thinking about how to connect the four batteries. Each terminal is difficult to reach with the thick 2/0 wire terminals. I was considering adding a terminal fuse to each battery to have something to bolt onto for easier access. I also saw a copper butt seam flag connector as well that might work, letting me create two large wires rather than 10 smaller ones to connect them all together.