12V system test

A couple weeks ago I started piecing together my 12V system for starting the controller and turning on the contactors. I also learned how to crimp16awg wire to various connectors. I am still not great at it, but getting better on each one. I decided to hook up a few traction pack batteries to the whole system and test it out. Here is a video of that test. It is short and I rushed through it because the camera was out of space on the memory card. I will explain more below.

There is a bit of confusion right from the start. This test is mainly a test of the 12V system in the car which normally runs the lights, accessories, radio, etc. It now will also turn on my motor controller and the contactors which switch the traction pack voltage into the controller. The meter on the right says like 16V. This meter is connected to the traction pack which is the high voltage battery pack that moves the car. For this test I hooked up (5) 3.2 volt traction batteries to the controller so I could spin the wheels after the 12V system did what it was supposed to do by turning on the controller and contactors.

So I found the wire that used to feed the solenoid for the starter. This wire is the output of the on position of the key switch. Exactly what I need to make the car function just like a normal car would. The only thing I don't use is the start position on the key switch. If you saw my previous post you will see I have the inertia switch and an emergency stop button in series after the key switch. If either of these safety items are disengaged the controller and secondary contactor will not turn on. I used the inertia switch as an on/off for this test so I didn't have to run to turn the key and then run back to try and catch the pre-charge and primary contactor switching on. As soon as I hit the inertia switch in the video, 12V is fed to the secondary contactor and controller and they both turn on. This sends traction pack negative voltage to the controller and also starts pre-charging the controller because the pre-charge resistors are across the terminals of the primary contactor which allows the pack positive to reach the controller but at a low current. The controller has a pre-charge timer in it that you can set to whatever time you want. I set it to 5 seconds for this test. The time should be set based on the size of your pre-charge resistors. I have an email somewhere which says what resistors I should use. The only drawback to this system is if for some reason the pre-charge does not happen and the timer expires and switches on the primary contactor, there will be a huge inrush of current and could fry the controller. The simplest solution is to wire a volt meter across the input of the controller so when you turn the key, if the voltage does not start climbing, you can turn off the key before the timer expires. When I hit the inertia switch you see the meter start climbing in voltage. This is the pre-charge.

So back to the sequence of events. The controller's pre-charge timer expires and sends 12V to the primary contactor and it switches on which will now allow for full current to be drawn from the batteries. Next, I hit the potbox throttle and the tires start turning. I did not have an ammeter hooked up in the video, so no idea how many amps it was drawing. I had the batteries hooked up with 16awg wire. If you look closely at the blue wire on the left when I hit the throttle, you will see it move. I don't think that is from the motor or transmission. I think it is the current flying through that little wire. Those wires were fairly warm when I was done with a few tests. When it is wired properly it will have 2/0 gauge wire which is pretty think and can handle the current.

One last item which I am updating. I had to move a few things slightly on my control board due to the hood latch which I did not have installed previously. I realized it might cause some issues with the control board and so I put it back on and sure enough it was running into the secondary contactor. I moved everything towards the firewall by an inch or so and that cleared the space. Here is the updated picture of the location of the components on the control board.

New layout w/hood latch in place

Tomorrow I will drill mounting holes for the controller and DC/DC converter because I believe they are in their final resting positions. I will also do a test crimp or two on the 2/0 battery cable and lugs. I realize it is a $4 connector, but I want to make sure I do it right before trying to make all the connections I need.