GAUGES FOR MY EV?

[Josh and Jenifer]

I'm having a little trouble sorting out what I need as far as gauges for my S-10 conversion.  Does anyone have any suggestions as to what works best?  I guess I would like to have a little computer screen,  RPM, Miles/Hr, battery pak voltage, Watt/Hrs used, etc.  But I'm not sure what is available,  I've been looking at stuff on the web so long, I've gotton myself confused.  

Thanks

Josh

www.jcsevparts.com
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[Bob Rice-2]

   Hi Josh;

   I'm old fashioned a bit here. I like plain old analog type panel meters.
Large format3-4" square. Usually install 12 volt "Grain of Wheat" type
bulbs, you model RR guyz know them. Any Hobby shop that sells parts would
know them, glue two of them inside the meter faces area. put them in series
so the'll last forever.I'm surprised at the relative lack of selection at
the EV parts depts. E Bay has a selection of stuff, IF you have time to wade
through it!? Got 3 600 amp Miller meters from welding gear? for 12 bux each.
Of course yur not done<g>! Gotta hunt down some 600 amp SHUNTS! Found them,
too. Shunts were cheep, too.All Electronics in CA. Volt meters, too, same
hunt thing!IF ya have a GOOD quality meter, like say, a Simpson, 60-70 bux,
nowadaze, you can get used to how your volts read, or how far yur gunna go!
Sorta like a sailer reads the wind on a sailboat, to trim his sails. Yur Amp
meter helps too, between the two you WILL learn how far yur going! How
"Soft" the pack is getting, FAR from home<g>!

   OK that's my "Beginner" pack. Read all that OTHER stuff, too. But don't
go crazy. Christ! There are ENOUGH diss-tractions driving nowadaze. Case in
point; Radios, that you need an engineering degree to operate! Just to turn
on, tune, you have to look at and diddle, you will not see the broad in the
Escalade on the fone blowing by the STOP sign, to take evasive action! I
sorta like my dashbored PLAIN, to keep an eye on traffic and the stupid shit
EVerybody else is pulling.

    YMMV, though.

     Bob
----- Original Message -----
From: "Josh Creel" <joshhcreel@...>
To: "Electric Vehicle Discussion List" <ev@...>
Sent: Monday, February 04, 2008 8:44 AM
Subject: [EVDL] GAUGES FOR MY EV?

> I'm having a little trouble sorting out what I need as far as gauges for
> my S-10 conversion.  Does anyone have any suggestions as to what works
> best?  I guess I would like to have a little computer screen,  RPM,
> Miles/Hr, battery pak voltage, Watt/Hrs used, etc.  But I'm not sure what
> is available,  I've been looking at stuff on the web so long, I've gotton
> myself confused.
>
> Thanks
>
> Josh
>
> www.jcsevparts.com
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
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[Frank John]

Josh,

I use an analog ammeter and voltmeter mounted in plain view.  You can calculate max speed in each gear so as to not overspeed your motor, so you don't necessarily need motor RPM (although this would be cool).  You can also use an E-Meter to keep track of AH out and AH in.  I think the ammeter and voltmeter are minimum requirements.

Devices like PakTrakr (?), EVision add capability but I don't feel I need them at this point.


----- Original Message ----
From: Josh Creel <joshhcreel@...>
To: Electric Vehicle Discussion List <ev@...>
Sent: Monday, February 4, 2008 8:44:02 AM
Subject: [EVDL] GAUGES FOR MY EV?


I'm
having
a
little
trouble
sorting
out
what
I
need
as
far
as
gauges
for
my
S-10
conversion.  
Does
anyone
have
any
suggestions
as
to
what
works
best?  
I
guess
I
would
like
to
have
a
little
computer
screen,  
RPM,
Miles/Hr,
battery
pak
voltage,
Watt/Hrs
used,
etc.  
But
I'm
not
sure
what
is
available,  
I've
been
looking
at
stuff
on
the
web
so
long,
I've
gotton
myself
confused.  

Thanks

Josh

www.jcsevparts.com
_______________________________________________
For
subscription
options,
see
http://lists.sjsu.edu/mailman/listinfo/ev





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[Roland Wiench]

Hello Josh,

I find that the most important gage for a EV is the motor amp meter.  This
gage takes off the a shunt that is install between the controller and the
motor.

Next is the battery amps which is taken from a shunt between the battery and
the main contactor.

Lets say your motor is rated for a continuous ampere of 200 amps, a battery
ampere meter will not read that. The battery amps may be reading 50 amps
while your motor may be at 200 amps.

Thinking your batteries are rated for 800 amps and you running the battery
ampere at 200 amps, your motor amperes could be way over 600 amps.

A motor like a ADC and Warp can only with stand a short burst of over ampere
for a short time, so motor ampere is the one to watch.  Many people have
overheat or burn out there motors because motor indications was not use.

The next meter is a meter to find out how much energy is use from the
battery and replacing that energy to the correct level and at what rate.

This would be like a E-Meter such as a Link-10. It reads the amount of
ampere-hour use and recharge, it also records the amount of watthours,
battery amperes, battery voltage, percentage of charge and battery
temperature.

The next meter would be a tachometer, so you do not over speed the motor.
Some controllers, have a speed sensor input where you input the maximum rpm
of the motor.

If you do not have a tachometer for now, here is a formula you can use to
find out what the maximum mph in each gear would be:


                               RPM x Tire Circumference
                       MPH  =  -------------------------
                               Overall Gear Ratio x 1056

The Overall Gear Ratio is axle ratio times the transmission gear ratio in a
selected gear.

The Tire Circumference is the one rolling turn with the weight of the
vehicle on the tire.  Is measure by placing a mark on the tire and the
ground and make one rotation and placing another mark on the ground.  Then
measure between the two marks.

For example, my motor maximum rpm is 6000 rpm and my tire circumference is
90 inches.  My rear axle is 5.57:1 and if I want to find out how fast I can
go in 1st gear which my is a 2.75:1, then to find the overall ratio, I take
5.57:1 times 2.75:1 = 15.3175:1 overall ratio.

So in 1st gear this becomes:


                             6000 rpm x 90 inches
                 33.3 MPH =  --------------------
                             15.3175  x 1056

Therefore I will normally not go over 30 mph in 1st gear.  You then can
calculated what the maximum speed you can go in all the other gears.

Roland

> ----- Original Message ----
> From: Josh Creel <joshhcreel@...>
> To: Electric Vehicle Discussion List <ev@...>
> Sent: Monday, February 4, 2008 8:44:02 AM
> Subject: [EVDL] GAUGES FOR MY EV?

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[Mark Ward-2]

Hi Roland,

My car uses an automatic transmission so I was planning to look at motor current to find the shift points.  What do you think of that approach?

Mark Ward
95 Saab 900 SE "Saabrina"
www.saabrina.blogspot.com


---- Roland Wiench <ev_7@...> wrote:

> Hello Josh,
>
> I find that the most important gage for a EV is the motor amp meter.  This
> gage takes off the a shunt that is install between the controller and the
> motor.
>
> Next is the battery amps which is taken from a shunt between the battery and
> the main contactor.
>
> Lets say your motor is rated for a continuous ampere of 200 amps, a battery
> ampere meter will not read that. The battery amps may be reading 50 amps
> while your motor may be at 200 amps.
>
> Thinking your batteries are rated for 800 amps and you running the battery
> ampere at 200 amps, your motor amperes could be way over 600 amps.
>
> A motor like a ADC and Warp can only with stand a short burst of over ampere
> for a short time, so motor ampere is the one to watch.  Many people have
> overheat or burn out there motors because motor indications was not use.
>
> The next meter is a meter to find out how much energy is use from the
> battery and replacing that energy to the correct level and at what rate.
>
> This would be like a E-Meter such as a Link-10. It reads the amount of
> ampere-hour use and recharge, it also records the amount of watthours,
> battery amperes, battery voltage, percentage of charge and battery
> temperature.
>
> The next meter would be a tachometer, so you do not over speed the motor.
> Some controllers, have a speed sensor input where you input the maximum rpm
> of the motor.
>
> If you do not have a tachometer for now, here is a formula you can use to
> find out what the maximum mph in each gear would be:
>
>
>                                RPM x Tire Circumference
>                        MPH  =  -------------------------
>                                Overall Gear Ratio x 1056
>
> The Overall Gear Ratio is axle ratio times the transmission gear ratio in a
> selected gear.
>
> The Tire Circumference is the one rolling turn with the weight of the
> vehicle on the tire.  Is measure by placing a mark on the tire and the
> ground and make one rotation and placing another mark on the ground.  Then
> measure between the two marks.
>
> For example, my motor maximum rpm is 6000 rpm and my tire circumference is
> 90 inches.  My rear axle is 5.57:1 and if I want to find out how fast I can
> go in 1st gear which my is a 2.75:1, then to find the overall ratio, I take
> 5.57:1 times 2.75:1 = 15.3175:1 overall ratio.
>
> So in 1st gear this becomes:
>
>
>                              6000 rpm x 90 inches
>                  33.3 MPH =  --------------------
>                              15.3175  x 1056
>
> Therefore I will normally not go over 30 mph in 1st gear.  You then can
> calculated what the maximum speed you can go in all the other gears.
>
> Roland
>
> > ----- Original Message ----
> > From: Josh Creel <joshhcreel@...>
> > To: Electric Vehicle Discussion List <ev@...>
> > Sent: Monday, February 4, 2008 8:44:02 AM
> > Subject: [EVDL] GAUGES FOR MY EV?
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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[Lee Hart]

Josh Creel wrote:
> I'm having a little trouble sorting out what I need as far as gauges
> for my S-10 conversion.  Does anyone have any suggestions as to what
> works best?  I guess I would like to have a little computer screen,
> RPM, Miles/Hr, battery pak voltage, Watt/Hrs used, etc.  But I'm not
> sure what is available,  I've been looking at stuff on the web so
> long, I've gotton myself confused.

The absolute minimum is an analog ammeter (battery amps) and voltmeter
(battery volts). An expanded scale voltmeter is good (like 100-150v for
a 120v pack). You can read them fast without taking your eyes off the
road. Once you learn what they mean, you can manage your batteries
pretty well.

Digital gauges are an improvement for voltage, because small difference
are important. Amps are more of a relative thing; digital tends to jump
around a lot and take longer to read (more time with your eyes off the
road).

Some form of state-of-charge ("fuel") gauge comes next. The cheap ones
are all basically voltmeters marked "Empty...1/4...1/2...3/4...Full".
Not very accurate, but neither are the gas gauges in most cars.

Engineers are interested in numbers, and want to measure all sorts of
things. Amphours, Kilowatts, Temperature, Number of Cycles on batteries,
etc. The E-meter / Link-10 is probably the best deal for the price, but
there are others.

Things really start to get complicated if you want to measure (or do
something about) individual battery voltages.

--
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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[Roland Wiench]

Hello Mark,

I have use both type of transmissions.  It was first a GM TH-350 with and
then without the torque converter.  The clutches only lasted 1000 miles with
out the torque converter.  I now use a GM TH-400 TCI automatic that is
converted to manual using a manual value body which is a shift only
transmission like a manual.

I use the large 4 inch tachometer that is converted to a motor ampere meter
by programming the Zilla for AMP ON TACH which I can read the motor ampere
on the tachometer.

I can pull away from 0 mph at a normal street acceleration and can keep it
at 200 motor amps on a level grade.  If there is a slight up hill grade, it
may go to 300 amps while holding the accelerator peddle at one constant
position.

I find as the speed increases from 0 to 30 mph on this slight up hill grade,
the motor ampere will go from 0 to 300 amps, and as it hits 300 amps, and
even while the speed is increasing, the motor ampere is now dropping from
300 amps back to 200 amps.

Now if the EV happens to be on level grade and then the GE 11 inch motor
will come down to 150 motor ampere while my battery ampere is about 50 amps.

Before I had a motor ampere meter install, I really cook the motor windings
to a nice dark brown color by just watching a battery ampere which read 180
battery amperes and the battery voltage was at 170 volts.

I found out, later when I install a motor amp meter, that I was pulling
about 600 motor ampere! on a long 2 mile up grade hill that ran for about 10
years.  I had a motor shop re enamel the windings and was able to run
another 15 years, until a silver solder welded connection came apart and had
that repair and re enamel again.

Using a motor amp meter, I now keep the GE-11 motor ampere to about a 175
amps normal running and the battery amperes at a 40 amps normal running at
30 mph.

The Warp 9 motor which I use as a back up spare motor, will run at 200 motor
amps at about 50 battery amps for the same speed.

Roland


----- Original Message -----
From: "Mark Ward" <thescreendoctor@...>
To: "Electric Vehicle Discussion List" <ev@...>
Cc: "Roland Wiench" <ev_7@...>
Sent: Monday, February 04, 2008 8:42 AM
Subject: Re: [EVDL] GAUGES FOR MY EV?

> Hi Roland,
>
> My car uses an automatic transmission so I was planning to look at motor
> current to find the shift points.  What do you think of that approach?
>
> Mark Ward
> 95 Saab 900 SE "Saabrina"
> www.saabrina.blogspot.com
>
>
> ---- Roland Wiench <ev_7@...> wrote:
> > Hello Josh,
> >
> > I find that the most important gage for a EV is the motor amp meter.
> > This
> > gage takes off the a shunt that is install between the controller and
> > the
> > motor.
> >
> > Next is the battery amps which is taken from a shunt between the battery
> > and
> > the main contactor.
> >
> > Lets say your motor is rated for a continuous ampere of 200 amps, a
> > battery
> > ampere meter will not read that. The battery amps may be reading 50 amps
> > while your motor may be at 200 amps.
> >
> > Thinking your batteries are rated for 800 amps and you running the
> > battery
> > ampere at 200 amps, your motor amperes could be way over 600 amps.
> >
> > A motor like a ADC and Warp can only with stand a short burst of over
> > ampere
> > for a short time, so motor ampere is the one to watch.  Many people have
> > overheat or burn out there motors because motor indications was not use.
> >
> > The next meter is a meter to find out how much energy is use from the
> > battery and replacing that energy to the correct level and at what rate.
> >
> > This would be like a E-Meter such as a Link-10. It reads the amount of
> > ampere-hour use and recharge, it also records the amount of watthours,
> > battery amperes, battery voltage, percentage of charge and battery
> > temperature.
> >
> > The next meter would be a tachometer, so you do not over speed the
> > motor.
> > Some controllers, have a speed sensor input where you input the maximum
> > rpm
> > of the motor.
> >
> > If you do not have a tachometer for now, here is a formula you can use
> > to
> > find out what the maximum mph in each gear would be:
> >
> >
> >                                RPM x Tire Circumference
> >                        MPH  =  -------------------------
> >                                Overall Gear Ratio x 1056
> >
> > The Overall Gear Ratio is axle ratio times the transmission gear ratio
> > in a
> > selected gear.
> >
> > The Tire Circumference is the one rolling turn with the weight of the
> > vehicle on the tire.  Is measure by placing a mark on the tire and the
> > ground and make one rotation and placing another mark on the ground.
> > Then
> > measure between the two marks.
> >
> > For example, my motor maximum rpm is 6000 rpm and my tire circumference
> > is
> > 90 inches.  My rear axle is 5.57:1 and if I want to find out how fast I
> > can
> > go in 1st gear which my is a 2.75:1, then to find the overall ratio, I
> > take
> > 5.57:1 times 2.75:1 = 15.3175:1 overall ratio.
> >
> > So in 1st gear this becomes:
> >
> >
> >                              6000 rpm x 90 inches
> >                  33.3 MPH =  --------------------
> >                              15.3175  x 1056
> >
> > Therefore I will normally not go over 30 mph in 1st gear.  You then can
> > calculated what the maximum speed you can go in all the other gears.
> >
> > Roland
> >
> > > ----- Original Message ----
> > > From: Josh Creel <joshhcreel@...>
> > > To: Electric Vehicle Discussion List <ev@...>
> > > Sent: Monday, February 4, 2008 8:44:02 AM
> > > Subject: [EVDL] GAUGES FOR MY EV?
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
>
>

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[Roger Stockton]

Lee Hart wrote:

> The absolute minimum is an analog ammeter (battery amps) and
> voltmeter (battery volts). An expanded scale voltmeter is
> good (like 100-150v for a 120v pack). You can read them fast
> without taking your eyes off the road. Once you learn what
> they mean, you can manage your batteries pretty well.

I'd suggest that if you have a modern controller then the absolute minimum is a voltmeter on the battery pack.  If the meter is analog, then expanded scale is pretty much essential, but if it is digital (e.g. just a DMM situated conveniently) you don't need an expanded scale.

If you have a contactor controller where *you* must control the current, then I would agree that a battery ammeter and voltmeter are the bare minimum.

Cheers,

Roger.

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[Lee Hart]

Roger Stockton wrote:
> I'd suggest that if you have a modern controller then the absolute
> minimum is a voltmeter on the battery pack...

You still need the ammeter, because voltage without knowing current is
largely meaningless.

--
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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[Roger Stockton]

Lee Hart wrote:

> You still need the ammeter, because voltage without knowing
> current is largely meaningless.

You've been driving with too many guages for too long! ;^>

Voltage on its own is *very* useful:

- when you hit 1.75V/cell under load, the battery is empty.  It doesn't help you at all to know what the current happens to be, since it is whatever it needs to be for your present driving conditions.  All you can do is stop and charge or reduce the load so the voltage remains at/above 1.75V/cell under load.  Again, as you reduce the load it doens't help one bit to know exactly how much current you are drawing since all that matters is that the  voltage is kept at/above this minimum.  After the EV has sat for some time, the unloaded voltage indication offers basic fuel guage capability.

- when driving, the voltage will sag with load, thus providing an indirect indication of the battery current.  You don't know just how much current you are drawing, but you can readily determine if you have reduced the current draw by shifting gear or easing up on the throttle based on whether the battery voltage sags further or rises in response to the change.

I stand by my claim that as long as you are using a controller with a current limit, then you can get by quite well without the battery ammeter.

Indeed, I think it is quite arguable that the first ammeter added to the system should probably be a motor current ammeter if the intent is to provide safety.  A battery side ammeter is very useful indeed, but it will not tell you anything about how you might be abusing the motor should you run in high gear at low speeds (low power and so low battery current but high and potentially damaging motor current).

Cheers,

Roger.

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[Paul-253]

On Feb 4, 2008, at 5:44 AM, Josh Creel wrote:

> I'm having a little trouble sorting out what I need as far as  
> gauges for my S-10 conversion.  Does anyone have any suggestions as  
> to what works best?  I guess I would like to have a little computer  
> screen,  RPM, Miles/Hr, battery pak voltage, Watt/Hrs used, etc.  
> But I'm not sure what is available,  I've been looking at stuff on  
> the web so long, I've gotton myself confused.

The first meter you *really* need is a volt meter. Either digital or  
analog with an expanded scale to show the range between 1.5 volts per  
cell and 2.5 volts per cell (or a little more.)

The second meter you need is a battery pack amp meter. If you have a  
contactor controller its as important as the volt meter but with a  
current regulated speed controller you can survive without it.

 From these basics there are many options that improve you knowledge  
while driving and make it easier to check at a glance. An E-meter or  
E-vision would provide a lot more useful information. Motor amps, or  
brush temperature gauges are good ways to keep an eye on just how  
hard you are working the motor. EVers are creative, there are a lot  
of other ideas!

I plan to install a digital volt and amp meter in place of the fuel  
and temperature gauge in my current conversion project. It has long  
skinny analog meters in there now that will provide a nice openings  
to install panel meters. I don't plan to install any others EV  
related instruments except that the Zilla controller will operate the  
ALT and OIL idiot lights. With experience you can tell a batteries  
state of charge pretty well just by what the actual voltage is at  
common current levels. A meter that tracks amps hours would be  
helpful while learning that :-) (actually, it would still be helpful!)

Paul Gooch

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[Roland Wiench]

When I contacted Otmar at Café Electric about a Zilla, he ask me what type
of EV do I have.  So I email him some photos of my EV and looking at the
dash, he said, where is your motor amp meter and how much battery ampere do
you normally pull?

I said, this is a triac Cable Form controller, and the amp meter shunt is in
series in the battery positive line that goes directly to the A1 motor
terminal. The battery negative goes to the main contactor that has a 300 amp
free wheel diode across it and then goes to the controller.

Otmar said the ampere will be different between the free wheel diode and the
motor.  This is the motor ampere which will be more than the battery ampere.

I said I normally pull 180 amps and some times 600 amps going up a steep 2
mile hill to work every day.  Otmar said to install a motor amp meter to see
what the motor pulls, so we know if you need a Zilla 1k or a Zilla 2k.  So I
did.

I took a test run up a slightly up grade hill that was 3 miles long, holding
the battery ampere to 90 amperes, and the about 300 motor amps at 30 mph at
6000 rpm.  So this is the ratio between the battery and motor ampere of
about 3 to 1.

Otmar then said you will need a Zilla 2k to be able to pull that 2 mile
steep hill which you may get over 300 batteries amps.  I said that is true,
if I keep it in final gear.

I said I will be retire by the time I modified these rig with a Zilla, so I
will not travel up the hill to work any longer. All my normal driving is in
city driving, which I now keep the continuous motor ampere at 200 amps and
the battery ampere of 75 amps.

So I choose a Zilla 1K because I would have to make the EV bigger to get it
in.  The Zilla 2K which I would like to have, would not fit in anyplace.

If you know what the ratio between your battery ampere and motor ampere,
with the type of motor controller you have, then you could RED LINE a
battery amp meter, to stay at a safe motor ampere.

Roland


----- Original Message -----
From: "Lee Hart" <leeahart@...>
To: "Electric Vehicle Discussion List" <ev@...>
Sent: Monday, February 04, 2008 4:04 PM
Subject: Re: [EVDL] GAUGES FOR MY EV?

> Roger Stockton wrote:
> > I'd suggest that if you have a modern controller then the absolute
> > minimum is a voltmeter on the battery pack...
>
> You still need the ammeter, because voltage without knowing current is
> largely meaningless.
>
> --
> 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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[Morgan LaMoore]

On Mon, Feb 4, 2008 at 5:45 PM, Roland Wiench <ev_7@...> wrote:

> If you know what the ratio between your battery ampere and motor ampere,
> with the type of motor controller you have, then you could RED LINE a
> battery amp meter, to stay at a safe motor ampere.


No. The ratio between battery amps and motor amps depends on the rpms and
torque; it changes while you drive.

If you're going slow but using lots of torque, there will be a big
difference and motor amps could be 10 times higher than battery amps, but if
you're going as fast as your motor will let you at that torque, the motor
amps and battery amps will be about the same. It all depends on the speed.

-Morgan LaMoore
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[Roger Stockton]

Roland Wiench wrote:

> I took a test run up a slightly up grade hill that was 3
> miles long, holding the battery ampere to 90 amperes, and the
> about 300 motor amps at 30 mph at 6000 rpm.  So this is the
> ratio between the battery and motor ampere of about 3 to 1.

> If you know what the ratio between your battery ampere and
> motor ampere, with the type of motor controller you have,
> then you could RED LINE a battery amp meter, to stay at a
> safe motor ampere.

I think there are two problems with this, though I agree it sounds good in theory.  First, there is the chicken and egg situation that you can't know the ratio of battery to motor current without having ammeters on both sides of the controller, and it seems a little pointless to install both in order to try to figure out how to avoid buying more than one of them ;^>

Second, there is the more fundamental problem that the ratio of motor current to battery current is not fixed; it varies depending on what the battery and motor voltages are.  At low speed, the current multiplication may be quite high since the motor volts will be low and the battery volts are high.  As the controller is just about to exit current limit, the battery volts and motor volts are nearly equal and the current multiplication will have dropped to about 1:1.

There is simply no way to mark a battery-side ammeter to give you any indication of safe motor current since there is no way to indicate that you are creeping along in 5th gear instead of 1st and are pumping full rated current through the motor while the battery current is still at a seemingly safe low level.  You might mark the battery ammeter with multiple "red lines", one for each gear (the way some speedos are marked with shift points for each gear), but this still wouldn't allow for the fact that the current multiplication decreases as the motor volts/RPM increase, and so you would be safe operating below these limits but would also limit yourself to a fraction of the available (safe) power at higher speeds.

Now, if you have a contactor controller, it has a fixed current multiplication of 1.0, so battery current *is* motor current, so a single ammeter can then cover both.

Cheers,

Roger.

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[Roland Wiench]

`That is true if you apply more torque at the slow speed, but I do not do
that, because I reduce my torque by shifting down. In final gear it will
start to become even if it can go that fast.

Here is the results in each gear that I record with my manual transmission
using a GE-11 motor at 6000 rpm.

1st gear ratio of 19.495:1 at 6000 rpm at 25 mph equals 161 motor amps at 65
battery amps.

2nd gear ratio of 13.925:1 at 6000 rpm at 35 mph equals 230 motor amps at 75
battery amps.

3rd gear ratio of 5.57:1 at 4000 rpm at 60 mph  equals  300 motor amps with
a battery ampere of 250 amps which is now becoming closer.

The estimate torque at very low speed of 10 mph is about 8 ft-lbs in 1st
gear and becomes about 50 ft-lbs at 60 mph in final gear.

Roland


----- Original Message -----
From: "Morgan LaMoore" <morganl@...>
To: "Electric Vehicle Discussion List" <ev@...>
Sent: Monday, February 04, 2008 5:02 PM
Subject: Re: [EVDL] GAUGES FOR MY EV?

> On Mon, Feb 4, 2008 at 5:45 PM, Roland Wiench <ev_7@...> wrote:
>
> > If you know what the ratio between your battery ampere and motor ampere,
> > with the type of motor controller you have, then you could RED LINE a
> > battery amp meter, to stay at a safe motor ampere.
>
>
> No. The ratio between battery amps and motor amps depends on the rpms and
> torque; it changes while you drive.
>
> If you're going slow but using lots of torque, there will be a big
> difference and motor amps could be 10 times higher than battery amps, but
> if
> you're going as fast as your motor will let you at that torque, the motor
> amps and battery amps will be about the same. It all depends on the speed.
>
> -Morgan LaMoore
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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