Electric Vehicle with No Starter Relay

2542 Views 7 Replies 4 Participants Last post by dtbaker, Feb 27, 2014

PSUstudent

Discussion Starter · Feb 25, 2014

The college I am at is currently revamping our electric vehicle. And while we do realize that in a normal vehicle (gas powered) there is normally a starter solenoid or relay. We were curious if the one in the vehicle was even needed. What would be the benefits/ downsides to having no starter relay in the vehicle. Instead, we were debating on going to a 2 switch system, where the initial switch is a single pull double throw, allowing us to turn on the peripherals (lights, music, etc.) and the second switch would turn on the controller, allowing for a double failsafe system. We are using a Curtis 1238r controller at the moment. Any advice would be greatly appreciated.

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Duncan

· #4 · Feb 26, 2014

PSUstudent said:
So is there any danger from a current spike when the power is first applied to the motor? A professor expressed his concern that this could be the case.

Yes - the motor controller has some large capacitors

Normal procedure is

Power the controller "brain" - normally 12v

power to one of the contactors
You will normally have a contactor (high power relay) in each leg of the battery

Pre-charge
If you close the second contactor you will get a damaging power surge
So you use a resister (I am using an old kettle element) to moderate that surge
When the voltage has climbed enough THEN you close the second contactor

Some controllers do this internally (Soliton)

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Duncan

· #6 · Feb 26, 2014

PSUstudent said:
I really appreciate the advice! We are using the curtis 1238r controller, but we were hoping that instead of the suggested setup, which has a relay set up to turn on when on switch is flipped, we could replace it with a switch and resistor to limit current to prevent the spike.

No you don't "replace it" with a switch and resistor to limit current
You use both

The switch and resistor are just for charging the capacitors - the main current is too much for a switch and is carried by the contactors

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