Brake cutoff levers and three speed switch

[donorcycle]

I am ordering parts for my first build using the "new version controller (IRFB3077, 36-48V) Infineon controller." I am wondering if I want/need a three speed switch and brake lever(s) that kill the power? Are they more trouble than what they are worth? I assume the less switch gear you have on the bike, the less there is to go wrong. Would some form of kill switch would be a good idea? If so, what do you guys recommend? I will be running 44.4 volts and not exceeding 25 MPH.

 

[jimw1960]

You only need the brake switches if you are going to set up with regen or if you have a cruise control throttle. They are a must in those cases but otherwise not needed. I also don't see any need for the three speed switch unless you just don't trust yourself to not go too heavy on the throttle.

 

[donorcycle]

Thanks,

I will be using a twist throttle, so I'm not sure why I would even want cruise control. Is there a reason?

So, worst case scenario, the throttle gets stuck and I need to stop, I will be able to overpower the motor by manually applying the brakes? I know it wouldn't be ideal, but what are the odds of the throttle sticking?

 

[jimw1960]

Cruise control is useful when you have long stretches of country road and want to be able to take your hand off the throttle without slowing down. I've never heard of a throttle getting stuck full on, but it is a remote possibility. Don't you have a key switch or on/off switch that cuts power to the controller? If that is not within easy reach, maybe at least one brake switch would be a good idea.

 

[number1cruncher]

A three speed switch may help if you find yourself limiting your throttle to below WOT most of the time. This is because the controller is most efficient and runs coolest when you are at WOT. If you don't care about energy efficiency or always run WOT, no need for one.

 

[amberwolf]

Ah, but the three speed switch still limits current exactly the same way that not being at WOT does--by not being at WOT.

So it doesn't help efficiency in that way.


It does help your hand not having to stay in what might be an awkward position, and it does limit the amount of power used up in starts from a stop and hard accelerations, depending on how your controller has the three speeds setup, it could be a significant savings of power, extending range.

If you want or need to be at the fastest speeds and hardest accelerations your bike is capable of, all the time, you wouldn't use the switch anyway.

If you intend to use a small battery pack but sometimes will want more range than you might normally get, the switch will help you do this by limiting all the parts of your usage that would use the most power, with the only user-action needed being switching over to one of those lower limits.