Paul & Sabrina's cheap DIY 144v motor controller

[jyanof]

Originally Posted by duncan

I would like a panic button that tells the controller to cut current,
(my software could fail at some point!)

Should I do this by putting a switch in the throttle pot line?
Or is this a feature that should be added to the new board?

I'm of the opinion that a hardware interruption is safer than a software feature. You should have some way of de-activating a contactor in your battery circuit.

This could be a manual switch that's accessible in the cabin, a button that deactivates a contactor solenoid, or a handle that's connected to a circuit breaker under the hood.

my setup uses the switch on the pot box to cut out the main contactor so that every time the pedal is released, the battery is disconnected (except for the precharge resistor). This has the added advantage of stopping the car at the first instinctual reaction of the driver if something goes wrong (by lifting the foot off the accelerator) and actually came in handy when some internals of my controller shorted out (see post above).

Keep in mind that not just the software can go bad and that no software will open a mosfet that failed shorted (or a bolt that wore through the insulation and bridged B- and M- like happened to me).

Use the potbox switch does present timing challenges (the controller motor output must begin after the contactor closes and end before it opens). One option may be to use this method during your initial testing and resort to a big red button afterwards.

anyway, hope that helps.

[duncan]

Hi Jyanof

I intend to use a main emergency disconnect - I have an old forklift connector that I am going to run a handbrake cable to

And I would switch off the main contactor - although I have heard of these welding shut

But these are both last resort actions

I was thinking of a stop button or throttle pot disconnecter as a less violent stop

But maybe that is bad thinking and I should go immediately to the emergency disconnect??

[sawickm]

Originally Posted by jpirkola

I have converted a Cub Cadet Garden tractor to EV.
Any suggestions or help is accepted.

Hi Jim,

You might want to check out this link: http://ecomodder.com/forum/showthrea...trak-9129.html

A EcoModder fourm member Ben Nelson restored a Elec-Trak tractor. He also shares in the ReVolt fourm and might give you some advice.

- Mark

[jyanof]

Originally Posted by duncan

I was thinking of a stop button or throttle pot disconnecter as a less violent stop

But maybe that is bad thinking and I should go immediately to the emergency disconnect??

hm, I'm just thinking that in an emergency, I'd like the first resort to be a very effective way of stopping the vehicle (pedal disengaging the main contactor, for me). I also have a manual circuit breaker whose handle is within reach of the driver. If that doesn't work, there are two fuses in the traction pack, but I'd have to stand on the brakes. I'm also reinstalling the clutch - depressing the clutch would stop the car, but also grenade my motor.

as an example, my controller failed when I was backing out of a space in a parking lot. with other cars just a few feet away, I'd have surely hit them if I did not have a quick way of shutting things down.

[bennelson]

My car is clutchless.
But it still has the clutch pedal.

I rigged the clutch pedal to a very large physical disconnect.

If I ever have a problem with the car, turning the key one click disconnects the main contactor (and doesn't lock up the steering.)

In event of an emergency, I can stomp on the clutch pedal, and it will turn the whole traction system off. (Also keep thieves from stealing the car, as the first thing the typical manual transmission drive does is push in the clutch.)

When I was doing the "test until failure" stage of testing on the original Open ReVolt, it finally failed right when I started the car in a parking lot.

Seems to me that if a controller is going to fail, right when you turn on the main contactor is a likely time. Kinda like how light bulbs usually burn out right when you flip the switch.

I always start my car with the gear selector in neutral. If the controller did fail, so what, you are parked, and just flip the key to off.

Jyanof, when your controller failed, were you already moving? Was it right after your turned your car on?

Learning how things break is the best way to learn how to improve them.

[jyanof]

Originally Posted by bennelson

Jyanof, when your controller failed, were you already moving? Was it right after your turned your car on?

Learning how things break is the best way to learn how to improve them.

I think my controller failed while sitting turned off in the parking lot after I got to work. Weird, I know, but I attribute the failure to thermal cycling and/or vibration. I didn't realize the failure (despite the warnings) until I started the car and pressed the pedal (which closed the main contactor).

If you haven't see it, there's a lot of details in this post, including the root cause and corrective action (ha, stole that buzzphrase from work).

joe's controller failure and fix

[bennelson]

Ah yes, I remember reading that.

My potentiometer has the micro-switch, which COULD be used to turn the main contactor on and off as you press or release the accelerator.

I do NOT have it hooked up that way. To me, that always seemed like overkill. And a lot of going "clack clack clack".

If you have the pot micro-switch rigged to the main contactor, that means that you already have the car in gear when your activate the main contactor. (Right? Why would you press the accelerator unless you wanted to drive?)

If you have a device that fails in the ON position, and it is most likely to fail right when you turn it on, and it gets turned on by being in gear and pressing the accelerator......

Hmm. Just doesn't sound like a good policy.
All gasoline cars are designed so that they have to be in park or neutral to turn them on.

An electric car should be the same way.


PS:
(In this case - "ON" means having the controller activated and connecting the main contactor.)

[dave koller]

Just a side note my pot has a switch I use to engage a latching relay that is to secondary contactor - it stays latched UNLESS I hit brake or clutch. Same idea but no clack clack. Even if it were to stick the key releases the primary and all or the E(mechanical)kill cable pulls it all apart...

[jyanof]

Originally Posted by bennelson

Ah yes, I remember reading that.

My potentiometer has the micro-switch, which COULD be used to turn the main contactor on and off as you press or release the accelerator.

I do NOT have it hooked up that way. To me, that always seemed like overkill. And a lot of going "clack clack clack".

To each his own... the contactor is barely audible and is a small inconvenience for the advantages provided, the most basic being that the motor will never get power unless commanded to by my foot.

If you have the pot micro-switch rigged to the main contactor, that means that you already have the car in gear when your activate the main contactor. (Right? Why would you press the accelerator unless you wanted to drive?)

If you have a device that fails in the ON position, and it is most likely to fail right when you turn it on, and it gets turned on by being in gear and pressing the accelerator......

Hmm. Just doesn't sound like a good policy.
All gasoline cars are designed so that they have to be in park or neutral to turn them on.

An electric car should be the same way.

I think you have a separate argument (starting the car in neutral) than actuating the main contactor with the pedal. I think the neutral thing is good practice, but I take a calculated risk with my setup by not doing so. If 150V is applied directly to my motor when it's in neutral, it'll overspeed and explode. I will never turn the car 'on' in neutral for this reason, but run the risk of the controller failing while in gear. Hence, the reason for my overkill pedal/contactor arrangement.

When my controller failed, I would've been out a $1500 motor too if I started in neutral. Others might accept this as a price for added safety, but instead, the cost was just a few electronic components despite being just as safe (as evidenced by actually experiencing a failure).

Additionally, I would argue that one of the controller's failure modes is something blowing when it first is commanded to conduct current after it has already been turned on. I think there have already been several examples in this thread of this (yours and mine are the only case I recall where something failed beforehand). In my case, the failure was unrelated to things getting switched on or off and could have easily happened while in the middle of driving. In this case, starting the car in neutral would not help and some sort of emergency disconnect is required. If there's not much room in the direction the car is going, things gotta disconnect fast!

So, I agree that starting in neutral is probably safest. I still argue that having the pedal actuate the contactor is also safest.

[bennelson]

The great thing about ANY custom project is that you can design it exactly how you want.

Overall EV design is ALWAYS going to say that you NEED an emergency disconnect - it's just common sense.

Although we have been talking much lately about wrecking controllers, etc., we don't mean to scare anyone off. EVs are actually SAFER that gasoline cars. How many gas cars do you know with an emergency OFF button? ( That could have come in handy with those Toyotas that while back.. )

In all seriousness though, anything homebuilt, designed by consensus, etc does not have the same level of testing and certification as if it were manufactured by a giant corporation.

It does allow us much greater flexibility, super-cool features, and lower cost then if a part was simply purchased.

And the fun and pride of doing it yourself!