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Allen_okc
07 May 2012, 0819
Are contacters necessary - and how much energy do they take away from the battery pack?

it just seems to me there is a better way to use a safety kill switch system - how about just use a manual power cut off switch and a off while on solenoid in case of a emergency shut down...

podolefsky
07 May 2012, 0942
Contactors are totally necessary. Mostly because they are designed to break thousands of amps in case of a fault. You could set something up that was normally closed and opened with voltage applied, but you need voltage to get it to open. A contactor that opens when you remove the voltage is more reliable, especially since you need it most when something went wrong.

They barely draw any power. A 24V LEV200 draws 0.6A, or about 14W. At cruise, a typical bike draws over 2000W, so it's <1% of total power. An EV200 is even less.

thesprocket26
07 May 2012, 0946
just a thought, if you were to crash your bike and it started to short, the contactor would open and hopefully prevent meltdown if it was drawing every amp possible. just in case you werent in the best condition to get up and hit the OFF switch ;-)

also, if you have the throttle wired through the contactor, the contactor will only be closing when you roll on the throttle. if your controller fails in the ON position, once you roll off the throttle it will break the field on the contactor coil and disco power to your controller/motor - preventing a runaway situation

Hugues
07 May 2012, 1051
....

also, if you have the throttle wired through the contactor, the contactor will only be closing when you roll on the throttle. if your controller fails in the ON position, once you roll off the throttle it will break the field on the contactor coil and disco power to your controller/motor - preventing a runaway situation

that sounds interesting, but i'm not completely sure i follow you, would you have a diagram showing how to wire the throttle this way ?
so you mean: the controller stops responding but it's still supplying power to the motor, then when you bring the throttle to the zero position, this would open the contactor ?
could this be done also through a switch on the brake lever ? or kill switch ? because in case of emergency, the first reflex is to press the brake lever, i think.

thanks for your help,

Allen_okc
07 May 2012, 1107
:o Thank You fellows - im with Hugues and his question...

my first reaction has always been grab the brake first...

good point Hugues...

Allen_okc
07 May 2012, 1111
in case of a accident, heaven forbid - drag racing your required to wear a break away key just in case of a accident...

Nuts & Volts
07 May 2012, 1158
in case of a accident, heaven forbid - drag racing your required to wear a break away key just in case of a accident...

And that lanyard/key will cause the contactor to open up

ARC EV Racing
07 May 2012, 1208
just a thought, if you were to crash your bike and it started to short, the contactor would open and hopefully prevent meltdown if it was drawing every amp possible. just in case you werent in the best condition to get up and hit the OFF switch ;-)


That's really the job of the main fuse - it opens if you get a short and protects the power circuit. It can only do that if it's between the pack and the fault though, which is why you need the fuse in the circuit as close to the pack as possible.

The contactor really needs to fail safe so that its default position is open. As Podolefsky said the power they draw is insignificant compared to the other demands on the pack.

thesprocket26
07 May 2012, 1255
sorry i wasnt more clear. I was assuming there is a fuse installed on the pack.

i think I also had Curtis/Sevcon controllers on my mind, and they have a seperate contactor for the traction leg of power that goes to your electric motor. So in a way, I was thinking that you would have two contactors installed (along with the assumed fuse). Main contactor to power up your controller, and a secondary that would make and break from controller M+ connection to your motor + connecton. maybe that is redundant.

also, depending on how you have your controller programmed (with a delay of M+ power?) you could have arcing on the pads of the secondary contactor(when it opens and closes), which would wear out and have to be replaced (contactor pads) from time to time

Allen_okc
07 May 2012, 1302
since the contactor doesn't use that much current, it seems to be the necessity of the system...

for the amount of heat they put out, seemed like it would eat a lot of current...

EVcycle
07 May 2012, 1621
Just ask Tammy,

She crashed her EV Bike at Rockingham (oil on the track) and the disconnect strapped to her wrist cut off all the power by removing the
voltage at the contactor. The bike stopped as apposed to catching fire, or running down the track without her.

I just happen to catch the event just as she went down..... :0
The back end is just starting to wash out from hitting the oil.
This is the first time anyone, even her, has seen this photo.


http://southernslingshots.com/The%20last%20ride%20012a.JPG


Keep the contactor!

CliC
07 May 2012, 1656
Are contacters necessary - and how much energy do they take away from the battery pack?

it just seems to me there is a better way to use a safety kill switch system - how about just use a manual power cut off switch and a off while on solenoid in case of a emergency shut down...

The contactor is very much like a solenoid; it's a coil/electromagnet that moves some metal prongs that make/break the power circuit. As for using it over a manual switch, the switch is only good for human intervention; the contactor is how the bike electronics can shut off main power if the need arises. And unlike solid-state devices, it is a "hard" switch that has passive failsafe (a spring opens the contacts when the coil is de-energized), making it somewhat more reliable in catastrophic failure power-interruption scenarios, as long as it hasn't been consistently overloaded to the point that the contacts weld.

I agree that the fuse is required as well. I'm not sure what the short-curcuit current availability on these packs is, but with industrial motor controls that I deal with our contactor rated for 100 or 200A switching is typically short-circuit protected by a breaker that can interrupt 65,000A.

Allen_okc
08 May 2012, 0515
geez ED - i hope she was alright!!! the track looks like it has a sheen on it too...

maybe it would be a good ideal to have a disconnect on the street bikes too... i thought about what would happen in case of a accident, bent parts are easy to fix compared to a motorcycle that burned to the ground...

Allen_okc
08 May 2012, 0519
Thank You CLIC - ive been there when those contacts have welded themselves to a closed circuit... semi trucks do it all the time...

Hugues
08 May 2012, 0747
...maybe it would be a good ideal to have a disconnect on the street bikes too... i thought about what would happen in case of a accident, bent parts are easy to fix compared to a motorcycle that burned to the ground...

I was discussing this with my bike shop, having a bracelet that will shut off the power if the contact is released.
But how many of you guys actually wear this, outside of racing ?
I guess you need to keep one hand on the handlebar at all time, or have a long enough cable so you can release your hand once in a while,
does not seem too comfortable.

How about a switch under the seat ?
If pressure is released, power is cutoff, makes sense ?
technically possible ?

Allen_okc
08 May 2012, 0918
i've learned most things are possible - the same sensor and another in the belt is used in your car to tell it you are not wearing a seat belt... the one in the seat is in the center of the bottom pad - the passenger doesnt need it...

but you can also get a radio type, like the system used in a harley davidson on the key start - without the trigger when trying to start the bike, it wont start...

EVcycle
08 May 2012, 1633
i've learned most things are possible - the same sensor and another in the belt is used in your car to tell it you are not wearing a seat belt... the one in the seat is in the center of the bottom pad - the passenger doesnt need it...

but you can also get a radio type, like the system used in a harley davidson on the key start - without the trigger when trying to start the bike, it wont start...


I like that idea......

EVcycle
08 May 2012, 1635
I was discussing this with my bike shop, having a bracelet that will shut off the power if the contact is released.
But how many of you guys actually wear this, outside of racing ?


It is more for racing. A required item for IHRA and NHRA.