Throttle Pedal

Over the last couple days I’ve figured out where I want the throttle pedal. I’m using a toyota prius hall effect sensor pedal. So this pedal takes 5v from a power supply and then sends out a 0-5 volt signal to the controller depending on position. I’m going to set up a “hot pedal” regen brake system. This means the regenerative braking will kick in as soon as I start taking my foot off the “gas” pedal and even before I hit the brakes. I’ve heard that the Tesla model S has this setup and people like it a lot. I’ve heard people say that it is worse for your efficiency because you don’t coast. Maybe, but the amount of energy used to spin the motor at the same speed as the drive wheels is probably only around 200 watts or less, which (although not a good thing) is pretty small compared with the 16,000 watt hour battery pack. I will monitor the motor as I start testing the car and if it seems that the free-spin draw is excessively high, I will switch over to the standard regenerative braking activated by the brake pedal. This will allow me to coast without any draw on the battery pack.

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To set up the throttle pedal, first I made an aluminum mount in the approximate shape that I would need. I cut it across the front so I could bend it at the bend in the firewall of the car. I bolted the aluminum where I wanted the pedal. Then I duct taped the pedal to the aluminum mount and tested using it. It turned out that it was too close to the brake pedal and I kept bumping it when “emergency” stepping on the brake.

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Next I modified the aluminum mount so that I could move the pedal over to the right slightly. I TIG welded the aluminum at the angle that I wanted it and bolted the pedal to it.

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In this final position I was no longer bumping the throttle while hitting the brake and the throttle was comfortable on my foot at all angles.

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Voila! I still have to hook up the wiring and run it to the controller, but the mount is solid and I like how it feels.

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2 thoughts on “Throttle Pedal

  1. You wrote – “Maybe, but the amount of energy used to spin the motor at the same speed as the drive wheels is probably only around 200 watts or less, which (although not a good thing) is pretty small compared with the 16,000 watt hour battery pack.”

    Please explain…thanks

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    1. Hey Donna,

      A 200 watt draw would take 80 hours to deplete a 16,000 Watt-hour battery pack because 200 Watts x 80 hours = 16,000 Watt-hours. That’s the math end. The other part is that I’m making an assumption about the physical resistance in the bearings of my motor and input shaft of my transmission. The more resistance these bearings have the more power will be necessary to continually overcome it.

      If you’re interested here is a primer on power and energy.

      So a watt is a measure of POWER consumption equal to a joule per second (notice that it is time dependent). It is a measurement of the RATE of energy being used. Back to the joule… A joule is a measure of ENERGY just like BTUs or calories, but it’s a really super small amount of energy so no one likes to talk about joules when talking about real world things like lightbulbs, microwaves or especially electric cars. For instance my electric car can store about 5,760,000,000 joules of energy in the battery pack. That’s inconvenient. Also if we want to get a sense of what kind of POWER we are using then seconds enters into this and during an hour car ride there are 3,600 seconds? Uhh…
      So it’s easier to use different units and also make use of handy metric prefixes.
      All this to say that kilowatt hours (kWh) are the easiest units to use here. 1 kWh is how much ENERGY (think joules) a 1kW POWER draw (like my motor) uses in 1 hour. It is also equivalent to the amount of ENERGY used by a 250 W (0.25kW) POWER draw for 4 hours. That’s easy math. 1 kW x 1 hour = 0.25 kW x 4 hours.

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