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Discussion Starter · #1 ·
Hi all,

I am beginning an EV conversion with a mini cooper from the early 2000s (I'm still trying to choose which year I want but I know it's going to be a model from 2002 - 2010) and I'm trying to make my first purchase for either one or two potentiometers. I've heard that it's good to use two potentiometers because it can be a safety to a faulty potentiometer giving a false reading to the controller, since both potentiometers must have the same readings for any power to be sent from the controller to the motor.

So essentially my question is: is it necessary that I purchase two potentiometers because of the risk of one potentiometer becoming faulty and telling the controller to send too much (or too little) power to my motor or should I just stick with one?

Please let me know what you think.
 

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This is very much your decision. Most conversions only use a single potentiometer. However, many OEM vehicles use two; of course they are concerned about safety over millions of miles, and also could be on the hook for liability if anything bad happens.
Does your controller support two?
Have you considered buying, say, a Prius pedal? Those incorporate two potentiometers and output a 0.8-3.6 volt signal.
 

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All production vehicles with an electronic accelerator control (which is probably all of them in production now) use one pedal assembly with redundant (dual) sensors in it. This is true whether they are electric vehicles, or hybrids, or just gasoline or diesel engine driven. Anyone specifying a single sensor for a production vehicle is incompetent or reckless and should be fired.

DIY conversions are designed and constructed to very different and much lower standards. You choose your level of risk tolerance. Potentiometers rarely fail (although wiring connections probably fail more frequently), and you might want to think about whether a failure would result in no power (annoying) or maximum power (dangerous).

If the controller can take redundant inputs and pedals with corresponding outputs (such as the one from a Prius mentioned by Isaac97) are readily available, I can't image choosing to settle for a single sensor.
 

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Discussion Starter · #4 ·
Thank you for the replies! The controller I'm using is a Zilla 1K with a hairball interface but I'm unsure if it can take redundant inputs and pedals with corresponding outputs. I did a bit of research on the controller and what it's capable of handling and I found this:

"Accelerator Potentiometer Requirements
The standard unit uses a regular 5K ohm, two wire potentiometer of the type used by Curtis and other controllers.
Any throttle assembly must have at least two return springs where either one is strong enough to return the pedal alone in case the other should break.
One the input to the Hairball, below 150 ohms is off, and over 4.8K ohms is full on. Resistance over 7K ohms will cause a fault condition.
Hairballs with the -P option use a magnetically coupled accelerator pedal assembly which can be bought with the controller. It includes the pedal assembly with dual hall effect sensors and dual internal return springs."

I'm new to the EV conversion world so I don't know if this blurb from the Zilla Manual is saying that the controller can support two pot boxes or if I have to by the pedal mentioned in the last paragraph to be able to use two.

Please let me know what you think this blurb from the Zilla Manual is saying, and what I can do, if anything, to be able to enable the controller to be able to take in redundant inputs and pedals with corresponding outputs.

Here's the link to the manual (info on pot box on pg. 6): https://evwest.com/support/zilla manual 2.02d.pdf
 

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Interesting! Do you have the -P option? That determines a lot of what is possible.

The 'standard' (no -P) requires a 2-wire potentiometer; rather than needing +, -, and signal, it's just wire 1 and wire 2. Thus the controller reads resistance rather than voltage.
With -P it reads voltage from the sensor; I can't tell whether you need their pedal, does the Zilla support throttle calibration?
 

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Hi all,

I am beginning an EV conversion with a mini cooper from the early 2000s (I'm still trying to choose which year I want but I know it's going to be a model from 2002 - 2010) and I'm trying to make my first purchase for either one or two potentiometers. I've heard that it's good to use two potentiometers because it can be a safety to a faulty potentiometer giving a false reading to the controller, since both potentiometers must have the same readings for any power to be sent from the controller to the motor.

So essentially my question is: is it necessary that I purchase two potentiometers because of the risk of one potentiometer becoming faulty and telling the controller to send too much (or too little) power to my motor or should I just stick with one?

Please let me know what you think.
Unrelated but have you watched Rich Rebuilds' mini cooper conversion videos? They might be helpful if you haven't.
 
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