# Hills and EVs - any issues?



## Tesseract (Sep 27, 2008)

skooler said:


> ..
> I found myself holding the car on a hill using a little bit of gas in the EV yesterday, completely static but drawing power...


This is called "hill holding" and it is brutal on a brushed motor. The current rating of the commutator and armature coils depends on them turning, so as to spread the heat losses out; when you stall the motor all of the current is concentrated into just a couple commutator segments and armature turns which can lead to rapid overheating, even at relatively low currents (ie - as low as 100A for more than a few seconds). The overheated commutator segments then tend to lift up the next time the motor is revved up, chipping or breaking the brushes.

And speaking of, the latest version of the Soliton code (1.5.2) can warn you if you are hill-holding. This new warning function was added primarily to alert you to a missing tach signal (ie - when motor current is flowing and the tach is enabled but no pulse received within a certain period), but the same situation occurs when hill-holding so it works equally well for that purpose, too.

Obviously, "brushless" motors (ie - AC) don't have this problem.


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## skooler (Mar 26, 2011)

Thanks Jeffrey,

I thought that would be the case. 

Force of habit I suppose, I realised I was doing it and then thought I'd ask the question.

I'll use the handbrake from now on.

We could do with an advantages and disadvantages section in the Wiki for each type of motor, clearly this is a disadvantage with series wound.


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## Zappo (Sep 1, 2011)

The overheating at the brushes and commutator obviously won't happen with an AC motor but there is still a real risk of overheating. AC systems would need to include a cooling system sized big enough to dissipate that heat when stalled. 

We have industrial applications where I work that have AC motors on flux vector VFDs where they are slow or stalled under load. A standard industrial AC motor can't dissipate the heat fast enough.


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## dragonsgate (May 19, 2012)

My first motor was held at a stop with power applied. It was not hill holding but the results was the same. The com got hot and afterward the motor sounded like a 10 speed coasting because the bars had lifted. I turned the bars down smooth but the motor armature was still junk. I use my left foot to hold the brake on hills and the right for the accelerator. It is almost second nature now.


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## skooler (Mar 26, 2011)

Hmmmm,

I don't like the idea of left foot braking - that puts me in the wrong mindset for road driving! It also switches the brake lights on which could dazzle anyone behind.

I'm going to see what holding it on the clutch at 500RPM or so feels like.

Where I live, pretty much every junction is on a slope so I'm going to have to find a way of doing it without risking damage to the motor.

Simple things!


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## dladd (Jun 1, 2011)

I just go quickly from brake to throttle. I roll back a little, but no more than I would if I were using a clutch. If it's really steep, I'll grab the hand brake so there is no gap between brakes and power.


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## GerhardRP (Nov 17, 2009)

skooler said:


> Hmmmm,
> 
> I don't like the idea of left foot braking - that puts me in the wrong mindset for road driving! It also switches the brake lights on which could dazzle anyone behind.


I do my braking with my right foot and hill holding and release with my left foot. Electric motors provide torque at zero RPM so there is no stall problem as with ICE.


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## dtbaker (Jan 5, 2008)

skooler said:


> Hmmmm,
> 
> I don't like the idea of left foot braking - that puts me in the wrong mindset for road driving! It also switches the brake lights on which could dazzle anyone behind.


if you are 'stopped', why would you not want your brake lights on?



skooler said:


> I'm going to see what holding it on the clutch at 500RPM or so feels like.


bad idea unless you want to replace clutch plate *often*. Just left-foot brake, or use hand-brake. yes its a different habit, but its a difference you can learn to enjoy.


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## McRat (Jul 10, 2012)

dtbaker said:


> if you are 'stopped', why would you not want your brake lights on?
> 
> 
> 
> bad idea unless you want to replace clutch plate *often*. Just left-foot brake, or use hand-brake. yes its a different habit, but its a difference you can learn to enjoy.


^^^^

Don't use a clutch for a brake. It's a bad habit to acquire.

I put my left edge of my right foot on the brake, then rotate my foot sideways to operate gas and brake simulatiously with a single foot, so I can downshift smoothly using my left foot for the clutch.


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## piotrsko (Dec 9, 2007)

I just roll up, let the motor RPM die, then switch to go pedal when light turns green. For [email protected]#$%^&* Hills, I use the E brake.


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## Woodsmith (Jun 5, 2008)

I am one who always uses the brake to hold a car on a hill. It is good practice.


Arch, when she first started driving my car, used to hold it on the clutch when on a hill. As an incentive to change her habit I threatened to give her the bill for the clutch/flywheel change (£600+) when she burned them. That stopped her!


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