[etischer]

Another nice feature would be to monitor bus voltage. If for some reason the precharge contactor or resistor failed, you don't want the main contactor to close.

Are those cube relays switching pack voltage or are they used to drive another contactor?

Originally Posted by DIYguy

Thank RF! Very nice. I'm in the middle of some basic mechanical stuff, but will be getting to the electrical controls through the winter. I have thought briefly about this timing requirement.... but due to current tasks, haven't pursued it. Are you building any of these devices for sale by chance?

I was thinking.... what might be nice is an output to drive an "idiot light" (pardon the expression...but it works for me lol) when the precharge time is satisfied.

I assume you are monitoring the vacuum pump to ensure that the brakes are fully functional before starting? Could, perhaps, the verification of this be a signal from a vacuum switch verifying adequate vacuum presence?

Regards,
Gary

[rfengineers]

Originally Posted by DIYguy

Are you building any of these devices for sale by chance?

Yes, I am building them for sale. Please contact me off list for details.

Originally Posted by DIYguy

I was thinking.... what might be nice is an output to drive an "idiot light" (pardon the expression...but it works for me lol) when the precharge time is satisfied.

A good idea. Assuming there is enough interest in the product, I will look into implementing it in a later version. Right now I just listen for the "clunk" of the contactor closing to tell me I am ready to go.

Originally Posted by DIYguy

I assume you are monitoring the vacuum pump to ensure that the brakes are fully functional before starting? Could, perhaps, the verification of this be a signal from a vacuum switch verifying adequate vacuum presence?

Yes, that is how it works. A signal from the vacuum switch (that turns the pump on-and-off in response to the vacuum level in the system) is used to indicate that the system is ready to go.

[rfengineers]

Originally Posted by etischer

Another nice feature would be to monitor bus voltage. If for some reason the precharge contactor or resistor failed, you don't want the main contactor to close.

Yes, that can be done but is a bit more complex. I am trying to put together a basic, affordable device. If there is interest I can work on a more sophisticated model.

Originally Posted by etischer

Are those cube relays switching pack voltage or are they used to drive another contactor?

The precharge relay switches the pack Voltage at low currents.
The contactor enable relay switches a ground for the contactor. The contactor Voltage could be 12V or pack Voltage. It depends on your EV's particular design.
The purpose of the external relays is to avoid bringing pack Voltage onto the circuit board.

[etischer]

I think it would be a good idea to check the rated voltage on the relays to make sure they are rated to switch high voltage. There is a certain liability when selling a product, it may be used in ways you haven't thought of, for which you may be liable if it fails. But like you, I am planning to sell my EV products once they are proven =) I'm gonna have to take out an umbrella insurance policy or something! I'm building an inverter for the Siemens/Ford AC motor.

There should be some feedback from the main contactor telling the drive that the contactor is closed. If the driver tries to drive off before the main contactor closes, all the power will go though the precharge resistor instead of the contactor. This could burn up the resistor, and cause some damage. I'm not trying to scare you off or be a jerk, just try to analyze the side effects of every possible failure. And remember no two EV's are alike in the DIY world.

Originally Posted by rfengineers

Yes, that can be done but is a bit more complex. I am trying to put together a basic, affordable device. If there is interest I can work on a more sophisticated model.


The precharge relay switches the pack Voltage at low currents.
The contactor enable relay switches a ground for the contactor. The contactor Voltage could be 12V or pack Voltage. It depends on your EV's particular design.
The purpose of the external relays is to avoid bringing pack Voltage onto the circuit board.

[rfengineers]

Originally Posted by etischer

I think it would be a good idea to check the rated voltage on the relays to make sure they are rated to switch high voltage. There is a certain liability when selling a product, it may be used in ways you haven't thought of, for which you may be liable if it fails. But like you, I am planning to sell my EV products once they are proven =) I'm gonna have to take out an umbrella insurance policy or something! I'm building an inverter for the Siemens/Ford AC motor.

There should be some feedback from the main contactor telling the drive that the contactor is closed. If the driver tries to drive off before the main contactor closes, all the power will go though the precharge resistor instead of the contactor. This could burn up the resistor, and cause some damage. I'm not trying to scare you off or be a jerk, just try to analyze the side effects of every possible failure. And remember no two EV's are alike in the DIY world.

Good point on the cube relays, I will check on that.

The controller will not run the motor on only the precharge resistor. If you demand any appreciable current the large drop across the precharge resistor will cause the controller to go into low-Voltage shutdown.

[electriKAT]

RF - please forgive my ignorance, but what is the drawback to leaving the pre-charge resistor on all of the time? Is it bad for the controller? Or dangerous? Initially I was thinking that it would drain your pack, but a capacitor is essentially an open circuit to DC current once it's charged, so that part should be negligible.

[rfengineers]

Originally Posted by electriKAT

RF - please forgive my ignorance, but what is the drawback to leaving the pre-charge resistor on all of the time? Is it bad for the controller? Or dangerous? Initially I was thinking that it would drain your pack, but a capacitor is essentially an open circuit to DC current once it's charged, so that part should be negligible.

That is an excellent question.

Many DIY'ers use a high-Voltage cutoff of some type, a circuit breaker or Anderson plug for example, and normally turn off their HV when the car is parked. The step-start prevents them from powering up in the wrong order.

For systems that always have HV applied to the contactor (such as my EV) it can be a shock hazard since it leaves high Voltage on the controller terminals even when the car is turned off.

There is nothing wrong with leaving it on all the time as long as your controller terminals are well guarded.

Joe

[dr01allen]

instead of a time delay, would it be useful to compare the voltage drop across the resistor? That way, regardless of resistance value, you know the capacitors are charged when it drops to 0.

[rfengineers]

Originally Posted by dr01allen

instead of a time delay, would it be useful to compare the voltage drop across the resistor? That way, regardless of resistance value, you know the capacitors are charged when it drops to 0.

That is a good idea that I may develop later. I wouldn't bother letting it go to zero. Just let it drop enough, say by half-or-so, so that there is less chance of arcing of the contacts.

[engineer_Bill]

Originally Posted by dr01allen

instead of a time delay, would it be useful to compare the voltage drop across the resistor? That way, regardless of resistance value, you know the capacitors are charged when it drops to 0.

I've heard of several people using a small wattage light either across the precharge resister, or as the resistor. When the light goes out the caps are charged.