# [EVDL] driving habits / efficiency



## EVDL List (Jul 27, 2007)

Hi folks,

Not sure where exactly I got the advise from but I've been following the
"put it in 2nd and forget it rule" most of the time (I never go above
40 mph). I shift to 3rd at about 30-35 mph. Somewhere I got it in my head
that using 1st gear would risk blowing my motor. And I've also been
complaining about poor range. Then today I found these "driving tips" in the
EVDL archive. They suggest I've been doing it all wrong:

http://www.evdl.org/docs/jet_driving_tips.pdf

These are apparently from the owner's manual that came with the Jet
Industries conversions. From a brief scan of the EV album it looks like
most of those cars used series wound DC motors (I have an ADC FB1-4001 -
also a series wound).

I went online and found a "maximum speed" calculator and using 5200 RPM
(conitinous value for 120V that I found somewhere) and my tire size, gear
ratios and final drive ratio, here are the max speeds it came up with:

1st = 25 mph
2nd = 44 mph
3rd = 67 mph
4th & 5th = faster than I'd ever want to drive.

Am I missing something? Should I be following the "tips" in the above .pdf
file?

- Peter Flipsen Jr
Pocatello, ID
http://www.evalbum.com/1974
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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

Using the conversion from rpm to mph in each gear is correct. If you do not 
have a rpm indicator them use the maximum mph at each gear.

My maximum motor rpm is 6000 rpm, but I stay about 500 rpm below that when I 
shift into the next gear.

In 1st gear my mph is 25 mph at 6000 rpm, so I shift to 2nd at 20 mph.
In 2nd gear my mph is 36 mph at 6000 rpm, so I shift to 3rd at 33 mph.
In 3rd gear my mph is 92 mph at 6000 rpm which I stay below that when I'm 
going down a long hill.

Here is a formula for converting rpm to mph:


Rpm x Tire circumference
Mph = ---------------------------
Gear Ratio x 1056


Tire circumference is measure as a rolling circumference. Put a mark on the 
tire and floor and roll the tire one turn and put another mark on the floor. 
Measure between these two marks in inches.

The Gear Ratio is the overall gear ratio which is multiplying the 
transmission gear times the differential gear.

If I try to pull away from a stop and accelerated up to 30 mph in 2nd gear, 
my motor ampere my peak at 600 amps and 150 battery amps. At 30 mph by 
motor amp is 150 amps with a battery amps of 65 amps.

Now starting out in 1st gear, the motor ampere gets between 200 to 300 amps 
and the battery amp is 75 amps to 100 amps.

My indicated motor torque at 25 mph in 1st gear is 9.5 ft.lbs while in 2nd 
gear, it is about 13 ft.lbs. The more torque the motor delivers, the more 
ampere is needed.

Roland



----- Original Message ----- 
From: "SLPinfo.org" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Wednesday, May 20, 2009 5:14 PM
Subject: [EVDL] driving habits / efficiency


> Hi folks,
>
> Not sure where exactly I got the advise from but I've been following the
> "put it in 2nd and forget it rule" most of the time (I never go above
> 40 mph). I shift to 3rd at about 30-35 mph. Somewhere I got it in my 
> head
> that using 1st gear would risk blowing my motor. And I've also been
> complaining about poor range. Then today I found these "driving tips" in 
> the
> EVDL archive. They suggest I've been doing it all wrong:
>
> http://www.evdl.org/docs/jet_driving_tips.pdf
>
> These are apparently from the owner's manual that came with the Jet
> Industries conversions. From a brief scan of the EV album it looks like
> most of those cars used series wound DC motors (I have an ADC FB1-4001 -
> also a series wound).
>
> I went online and found a "maximum speed" calculator and using 5200 RPM
> (conitinous value for 120V that I found somewhere) and my tire size, gear
> ratios and final drive ratio, here are the max speeds it came up with:
>
> 1st = 25 mph
> 2nd = 44 mph
> 3rd = 67 mph
> 4th & 5th = faster than I'd ever want to drive.
>
> Am I missing something? Should I be following the "tips" in the above 
> .pdf
> file?
>
> - Peter Flipsen Jr
> Pocatello, ID
> http://www.evalbum.com/1974
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> Usage guidelines: http://evdl.org/help/index.html#conv
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> 

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## EVDL List (Jul 27, 2007)

Jet Industries lists 20 HP @ 4900 RPM for the Electrica.

For my car with oversize tires this calculates out to

1st gear 27.4 MPH

2nd gear 47.9 MPH

3rd gear 79.8 MPH

4th gear Not calculated or used.

The sun visor in the car list Max Speed as

1st gear 20 MPH

2nd gear 35 MPH

3rd gear 55 MPH

4th gear 55+

For constant speed minimum current draw is about 5 MPH slower
than these listed speeds.

Starting in 2nd gear produces the maximum acceleration, and
maximum current drain.

John in Sylmar, CA
www.evalbum.com/1749

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## EVDL List (Jul 27, 2007)

Thanks for your responses guys - this morning on my way into work I tried
starting out in first and using my usual gentle foot on the accelerator I
did not smoke the tires. Acceleration is a bit slower overall but I did
very definitely notice that I don't get the big spike to 400+ Amps that I
was getting when I started off in 2nd - it's now much closer to 200-225 and
it quickly drops to around 100. Switching to 2nd at 20 mph or so I get
another spike to 250 Amps or so but again it drops off quickly especially on
flat terrain (not that easy to find here). But the engine / transmission
"whine" is clearly much louder than before. Will see if driving this
way helps the range much.

Not sure if it will help the whine or not, but I hope to switch to synthetic
tranny fluid soon.

btw Roland - I do have a hall effect tach ready to install so hopefully I'll
be able to see actual RPM soon.

- Peter




> JS <[email protected]> wrote:
> 
> > Jet Industries lists 20 HP @ 4900 RPM for the Electrica.
> >
> ...


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## EVDL List (Jul 27, 2007)

> SLPinfo.org wrote:
> 
> > Thanks for your responses guys - this morning on my way into
> > work I tried starting out in first and using my usual gentle
> ...


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## EVDL List (Jul 27, 2007)

Roger,

You're not the first to suggest this - Cor van de Water was even so nice as
to send me a very simplified wiring diagram some time ago for doing the
change. I tend to avoid "tinkering" as much as possible as I am neither an
engineer nor a mechanic (I had the conversion done by someone else). And
the car is zero emission transportation for me, not a "project" or a "hobby"
as it is for many on this list (I don't mean to imply that the hobbyists
aren't also concerned about the environment but it's a question of different
perspectives and very definitely different skill levels). But I am slowly
getting a little more comfortable with making little changes as I learn more
about the car and so I may yet attempt it.

- Peter



> Roger Stockton <[email protected]>wrote:
> 
> > SLPinfo.org wrote:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

Roger,

Just thought about this some more. I don't yet have a tach installed. I'm
looking at motor amps not RPM (although I clearly hear the faster motor
speed). But it was my understanding that battery amps would never be higher
than motor amps (although they could be the same). Is that not true?

- Peter



> SLPinfo.org <[email protected]> wrote:
> 
> > Roger,
> >
> ...


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## EVDL List (Jul 27, 2007)

> SLPinfo.org wrote:
> > You're not the first to suggest this - Cor van de Water was even so nice as
> > to send me a very simplified wiring diagram some time ago for doing the
> > change. I tend to avoid "tinkering" as much as possible as I am neither an
> ...


----------



## EVDL List (Jul 27, 2007)

> SLPinfo.org wrote:
> 
> > You're not the first to suggest this - Cor van de Water was
> > even so nice as to send me a very simplified wiring diagram
> ...


----------



## EVDL List (Jul 27, 2007)

> SLPinfo.org wrote:
> 
> > Just thought about this some more. I don't yet have a tach
> > installed. I'm looking at motor amps not RPM (although I
> ...


----------



## EVDL List (Jul 27, 2007)

Roger,

That's a very helpful explanation - thanks. I actually have a tachometer
though I haven't installed it yet (another bit of tinkering I've been
avoiding) which would help me monitor what's happening with the motor at
least indirectly if I moved the shunt.

Unfortunately having the "converters" move the shunt is not practical as
they are 2 1/2 hours away in Salt Lake City and I don't have an easy way to
get the car there.

Bottom line seems to be that if I really want to have a better handle on the
most efficient way to drive the car, I may just have to dive in and tinker
so I can obtain the right data. I'm not totally inept but just inexperienced
and lacking a little confidence.

Thanks again.

- Peter



> Roger Stockton <[email protected]>wrote:
> 
> > SLPinfo.org wrote:
> >
> ...


----------



## EVDL List (Jul 27, 2007)

I'd offer to come help you, but I dont leave Boise very often. Were
you planning to bring your EV to the Idaho Green Expo? If so I could
help you then, though it is 3 months away.

-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555





> SLPinfo.org <[email protected]> wrote:
> > Roger,
> >
> > That's a very helpful explanation - thanks. I actually have a tachomet=
> ...


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## EVDL List (Jul 27, 2007)

Don't know what or where that is so clearly I had no plans.

- Peter



> Jon Glauser <[email protected]> wrote:
> 
> > I'd offer to come help you, but I dont leave Boise very often. Were
> > you planning to bring your EV to the Idaho Green Expo? If so I could
> ...


----------



## EVDL List (Jul 27, 2007)

First, I assumed you are they guy in Twin Falls, ID. If not, then my mistak=
e!

the Green Expo is this: http://www.idahogreenexpo.org/

in Boise on July 18-19. Last year we had 4 EVs there. This year there
may be as many as 9, if everyone can make it (more likely ~5).

-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555





> SLPinfo.org <[email protected]> wrote:
> > Don't know what or where that is so clearly I had no plans.
> >
> > - Peter
> ...


----------



## EVDL List (Jul 27, 2007)

Nope - I'm in Idaho, but I'm over in Pocatello.

- Peter
http://www.evalbum.com/1974



> Jon Glauser <[email protected]> wrote:
> 
> > First, I assumed you are they guy in Twin Falls, ID. If not, then my
> > mistake!
> ...


----------



## EVDL List (Jul 27, 2007)

ahh, thats right, Wayne Anderson (http://www.evalbum.com/1397) is in
Twin Falls. I wonder if he might be willing to help you out?

-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555





> SLPinfo.org <[email protected]> wrote:
> > Nope - I'm in Idaho, but I'm over in Pocatello.
> >
> > - Peter
> ...


----------



## EVDL List (Jul 27, 2007)

Jon,

Not sure if I need the help, really. If I decide to move the shunt I
actually think I can manage it. I just have to make the decision and set
aside some time for it. It's like my tach - I can probably figure it out,
but I just have to do it.

But, ultimately this whole discussion was really about how I should be
driving the car. Should I just start in second gear all the time and forget
it, or follow the guidance in the Jet Electric manual I found in the EVDL
library where I would start in first? I've been doing the latter for 2
days now (start in 1st and shift to 2nd at 20-25 mph; I would shift to 3rd
at 40 mph if I ever got going that fast; I do put it in 3rd when going down
some of the steep hills here). I already notice that the "motor amps" no
longer spike much above 200-225. That gives me hope that my next set
of batteries could be gels and I wouldn't burn them out prematurely (in that
case of course I would definitely want to move the shunt or put in a second
one and a switch on my gauge).

The whine of the revving engine in 1st gear (though I may be imagining this)
also appears to be lessening somewhat. I wonder if by avoiding first (which
I never used before a few days ago) I did not break the motor in properly
(or, God forbid, maybe I did some damage). With just over 1000 EV miles on
it the motor should be broken in by now but ...

- Peter



> Jon Glauser <[email protected]> wrote:
> 
> > ahh, thats right, Wayne Anderson (http://www.evalbum.com/1397) is in
> > Twin Falls. I wonder if he might be willing to help you out?
> ...


----------



## EVDL List (Jul 27, 2007)

When I drove a '74 Honda Civic with a Prestolite motor, I found that there 
was no point to using first gear. The gearing in that trans was so low that 
the motor torque curve fell off before I was more than barely rolling. I 
usually drove in second gear round town, and in third at higher speeds. I 
seldom used fourth.

Newer cars are often geared higher, so it might make more sense to use first 
gear with those vehicles. 

There is a somewhat greater danger of overspeeding the motor in the lowest 
gears. 

>From what I've seen, and others' experience may be different, if you are 
operating a series motor at its rated voltage it's unlikely to overspeed 
under load regardless of gear. The back-EMF seems to limit RPM naturally. 
However, most EV hobbyists run their motors above rated voltage (as much as 
double the rated voltage). And, as I say, my admittedly limited experience 
may not be either indicative or prescriptive.

David Roden - Akron, Ohio, USA
EVDL Administrator

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----------



## EVDL List (Jul 27, 2007)

> Not sure where exactly I got the advise from but I've been following 
> the "put it in 2nd and forget it rule" most of the time (I never go 
> above 40 mph). I shift to 3rd at about 30-35 mph. Somewhere I got 
> it in my head that using 1st gear would risk blowing my motor. And 
> I've also been complaining about poor range.

This is how I tell my wife to drive my EV. She's used to automatics, and
doesn't like shifting. It isn't the most efficient way to drive, but is
simple and works OK. Here's my reasoning:

You could blow your motor in 1st gear if you simply "floored it". The
car would keep on accelerating until motor speed got so high that it
blew up. The same thing would happen to your ICE vehicle if there
weren't an RPM limiter in the computer. So, the easy advice is "don't
use 1st gear".

In second gear, most lower-powered EVs won't go fast enough hurt the
motor. My LeCar will get up to perhaps 50 mph in 2nd if you leave it
floored long enough; that's about 6000 rpm which is tolerable for an ADC
L91 6.7" motor. And, it still accelerates well and can still climb any
reasonable hill in 2nd gear.

Third gear allows a higher top speed; but you don't have enough starting
torque to accelerate or climb hills. 4th gear is essentially useless; 
you never drive fast enough to need it, and using it at lower speeds 
makes the motor turn so slowly that it doesn't get adequate cooling.

So the easy advice is "use 2nd gear up to 40 mph or so, then 3rd gear 
above that."

> Then today I found these "driving tips" in the EVDL archive.
> They suggest I've been doing it all wrong:
> http://www.evdl.org/docs/jet_driving_tips.pdf

Jet's guidelines will work as well; but they have their own set of 
unstated assumptions and limitations.

On page 1, it confuses motor current with battery current. It says "An 
electric motor running at its fastest safe RPM will draw the lowest 
current. This is equivalent to low fuel flow in an ICE."

It's *battery* current that is equivalent to fuel flow in an ICE. For 
best efficiency, you drive so *battery* current is the lowest. This is a 
*different* point than the one that produces the lowest motor current 
(motor current is in general *higher* than battery current).

The Jet vehicles had the ammeter in series with the *battery* -- not the 
motor. When they mention current in the rest of the paper, all of their 
current readings are battery current, not motor current.

They are assuming golf cart batteries, which is why they suggest keeping 
the current below 250 amps.

The Jets had GE EV-1 SCR controllers. The EV-1 is not particularly 
efficient at light throttle, and is the most efficient at full throttle 
when the bypass contactor is closed. Thus, they emphasize shifting to 
keep motor RPM high so they can keep the controller as close to full-on 
as possible. This is why their "driving tips" suggest starting in 1st 
gear instead of 2nd, and shifting to keep the motor at higher RPM.

Modern controllers are more efficient at light throttle, so it's not as 
important to keep motor speed high. Modern AGM batteries have a lower 
internal resistance so higher currents are more practical. In my own EV, 
efficiency is better if I don't use full throttle and wind the motor RPM 
up too high, because losses from the internal fan lower efficiency.

Ultimately, you need to watch your own ammeter, and figure out for 
yourself what gear is the most efficient at each speed in your EV.

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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