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Electric Vehicle with No Starter Relay

2542 Views 7 Replies 4 Participants Last post by  dtbaker
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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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

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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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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