range meter or ?

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range meter or ?

themotorman
Unless the route can be programmed into the range meter system, via
integrated GPS unit, and all the battery parameters, plus driving/battery
usage history, then a range meter will be an inaccurate beast. However
something that says you have used 3/4 of capacity would be helpful and that
is doable.
My car has an old style fuel gage of the kind used in 1930's gas guzzlers
and I will make sure that "empty" on the gage still gives me a 1/4 capacity.
Since I do not plan on anything more than being 30 miles from home, and my
friends have cell phones getting home will not be a problem. There is also
the tow truck!! Yucky, but still what I had to use with my ICE when the
timing chain broke!
Expecting complex electronics to solve all ones problems is INMNSHO is not a
direction that hobbyists need to pursue. Better to concentrate on the fun
stuff..


--
When all else fails, remember failure is the success of knowing what not to
do.
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Re: range meter or ?

dave cover-2
Why can't a simple module take your current usage and and then
estimate range based on remaining pack capacity? If you are using X
W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
of range.

Isn't it that simple?

DAC

On Thu, Jul 1, 2010 at 2:08 PM, ron doctors <[hidden email]> wrote:

> Unless the route can be programmed into the range meter system, via
> integrated GPS unit, and all the battery parameters, plus driving/battery
> usage history, then a range meter will be an inaccurate beast. However
> something that says you have used 3/4 of capacity would be helpful and that
> is doable.
> My car has an old style fuel gage of the kind used in 1930's gas guzzlers
> and I will make sure that "empty" on the gage still gives me a 1/4 capacity.
> Since I do not plan on anything more than being 30 miles from home, and my
> friends have cell phones getting home will not be a problem. There is also
> the tow truck!! Yucky, but still what I had to use with my ICE when the
> timing chain broke!
> Expecting complex electronics to solve all ones problems is INMNSHO is not a
> direction that hobbyists need to pursue. Better to concentrate on the fun
> stuff..
>
>
> --
> When all else fails, remember failure is the success of knowing what not to
> do.
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Re: range meter or ?

Ben-149
On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
> Why can't a simple module take your current usage and and then
> estimate range based on remaining pack capacity? If you are using X
> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> of range.
>
> Isn't it that simple?
>
> DAC
>

Simple, but not accurate in most real-world cases. Say you used half
your energy driving 15 miles downhill and away from home. Your gauge
would estimate another 15 miles range remaining, but you wouldn't make
it if you tried to return home (now going uphill).

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Re: range meter or ?

Stephen Chapman
In reply to this post by dave cover-2
Calculating the past power used is relatively easy and relatively accurate.
Calculating future power use is a very nearly a shot in the dark and
therefore not a good indicator of range..
Stephen Chapman

On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:

> Why can't a simple module take your current usage and and then
> estimate range based on remaining pack capacity? If you are using X
> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> of range.
>
> Isn't it that simple?
>
> DAC
>
>
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Re: range meter or ?

dave cover-2
In reply to this post by Ben-149
Yes but, if you have your foot into the throttle more to go up hill,
the range estimator should show the you have less range. Remaining
capacity divided by current rate of use. Not rocket surgery.

DAC

On Thu, Jul 1, 2010 at 2:25 PM, Ben <[hidden email]> wrote:

> On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
>> Why can't a simple module take your current usage and and then
>> estimate range based on remaining pack capacity? If you are using X
>> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
>> of range.
>>
>> Isn't it that simple?
>>
>> DAC
>>
>
> Simple, but not accurate in most real-world cases. Say you used half
> your energy driving 15 miles downhill and away from home. Your gauge
> would estimate another 15 miles range remaining, but you wouldn't make
> it if you tried to return home (now going uphill).
>
> _______________________________________________
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>



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Re: range meter or ?

dave cover-2
In reply to this post by Stephen Chapman
But you don't use "future use." You just take the current rate of use.
That will go up and down as you press or release the throttle. Drive
harder, less range. Drive easier, more range.

DAC

On Thu, Jul 1, 2010 at 2:29 PM, Stephen Chapman <[hidden email]> wrote:

> Calculating the past power used is relatively easy and relatively accurate.
> Calculating future power use is a very nearly a shot in the dark and
> therefore not a good indicator of range..
> Stephen Chapman
>
> On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
>
>> Why can't a simple module take your current usage and and then
>> estimate range based on remaining pack capacity? If you are using X
>> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
>> of range.
>>
>> Isn't it that simple?
>>
>> DAC
>>
>>
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Re: range meter or ?

Stephen Chapman
In reply to this post by dave cover-2
LOL, then it is too late.  The range meter would only tell you that you were
not going to make it.  The apparent range would fluctuate wildly with every
accel/decel, uphill/downhill.  What good is that?
Stephen Chapman

On Thu, Jul 1, 2010 at 2:31 PM, dave cover <[hidden email]> wrote:

> Yes but, if you have your foot into the throttle more to go up hill,
> the range estimator should show the you have less range. Remaining
> capacity divided by current rate of use. Not rocket surgery.
>
> DAC
>
> On Thu, Jul 1, 2010 at 2:25 PM, Ben <[hidden email]> wrote:
> > On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
> >> Why can't a simple module take your current usage and and then
> >> estimate range based on remaining pack capacity? If you are using X
> >> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> >> of range.
> >>
> >> Isn't it that simple?
> >>
> >> DAC
> >>
> >
> > Simple, but not accurate in most real-world cases. Say you used half
> > your energy driving 15 miles downhill and away from home. Your gauge
> > would estimate another 15 miles range remaining, but you wouldn't make
> > it if you tried to return home (now going uphill).
> >
> > _______________________________________________
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> >
>
>
>
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Re: range meter or ?

Stephen Chapman
In reply to this post by dave cover-2
Range is a function of future use.  I have a range indicator as part of the
trip computer in my ice.  It can be easily fooled by driving habits and my
rate of gas consumption does not really change that much.  The power used by
an EV can easily change by a factor of 4-5.

On Thu, Jul 1, 2010 at 2:33 PM, dave cover <[hidden email]> wrote:

> But you don't use "future use." You just take the current rate of use.
> That will go up and down as you press or release the throttle. Drive
> harder, less range. Drive easier, more range.
>
> DAC
>
> On Thu, Jul 1, 2010 at 2:29 PM, Stephen Chapman <[hidden email]>
> wrote:
> > Calculating the past power used is relatively easy and relatively
> accurate.
> > Calculating future power use is a very nearly a shot in the dark and
> > therefore not a good indicator of range..
> > Stephen Chapman
> >
> > On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
> >
> >> Why can't a simple module take your current usage and and then
> >> estimate range based on remaining pack capacity? If you are using X
> >> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> >> of range.
> >>
> >> Isn't it that simple?
> >>
> >> DAC
> >>
> >>
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>
>
>
> --
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>
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Re: range meter or ?

Collin Kidder
In reply to this post by dave cover-2
  Well, it's much more complicated than that. Obviously I've been on
record as saying I don't think it has to be quite as complicated as
other people have suggested but it's still very close.

Most people still think that a "fuel" type gauge is advantageous and
doable. A range gauge is nothing other than a fuel gauge that also tries
to figure out how far you have to go. It can try to do this by
calculating how far you have gone so far and extrapolate from there
based on the current fuel gauge reading. Of course, in an EV the fuel
gauge almost always lies. This is as opposed to an ICE where the gas
gauge is likely reasonably accurate. This is the first big complication.
A potential solution is to keep track of how long it takes to get to the
20% mark (for lithium cells. Assume I mean LiFePO4 cells when I talk
about batteries from now on.) Once you get to 20% you look at how many
Ah you've used. If the pack is getting weaker then this # will steadily
go down. Unfortunately this requires one to drain the pack quite far.
But did you ever wonder why people tell you to drain your laptop or
cellphone battery all of the way and then recharge fully to recalibrate
the remaining power gauge? The same thing would help to calibrate the
fuel gauge on a lithium pack. It would have to be done periodically
especially when it is suspected that the fuel gauge is telling lies. One
can also try to compensate for temperature but in an EV batteries tend
to be spread out over a large area and potentially over multiple
locations. This makes getting temperature readings much more
complicated. Potentially each cell should have a thermometer. In
addition, batteries, even lithium ones, suffer from peukert factor and
thus will not give up the same # of Ah if subjected to differing loads.
Luckily this effect is small in lithium batteries but it still exists.
Add that all up and the fuel gauge idea even starts to seem complicated.
However, I think that a reasonable guess is possible. The big catch is
that a lithium pack which hasn't been monitored closely enough could
jump from 30-40% down to 20% all at once when the monitoring system
detects that it got to a voltage knee.

Now that the likely inaccurate fuel gauge has been covered, what about
the distance calculation? Well, if the upcoming trip is done on the same
sort of roads, grade, speed as the first part then the calculation will
be very easy. It would be simple extrapolation and it would be very
accurate. Unfortunately life doesn't always work that way. Maybe the
first part was pretty flat and 45MPH but the upcoming part of your trip
is very mountainous and 40MPH. This will make the calculation much more
complicated. The range meter will think you have a lot more range than
you really do. So what to do? Well, the range meter will have to "cheat"
and take away range at a much faster rate than you are really traveling.
At some point hopefully you realize that fact and adjust your plans
accordingly. The range gauge has to trend the data to see how many amps
you have been drawing lately in order to get a guess as to how much
further you can go. This will necessarily jump around a bit if you
change driving patterns.

In essence, a range gauge is nothing but a very sophisticated crystal
ball. Even a fuel gauge for an EV is really just a guess.

On 7/1/2010 2:19 PM, dave cover wrote:

> Why can't a simple module take your current usage and and then
> estimate range based on remaining pack capacity? If you are using X
> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> of range.
>
> Isn't it that simple?
>
> DAC
>
> On Thu, Jul 1, 2010 at 2:08 PM, ron doctors<[hidden email]>  wrote:
>> Unless the route can be programmed into the range meter system, via
>> integrated GPS unit, and all the battery parameters, plus driving/battery
>> usage history, then a range meter will be an inaccurate beast. However
>> something that says you have used 3/4 of capacity would be helpful and that
>> is doable.
>> My car has an old style fuel gage of the kind used in 1930's gas guzzlers
>> and I will make sure that "empty" on the gage still gives me a 1/4 capacity.
>> Since I do not plan on anything more than being 30 miles from home, and my
>> friends have cell phones getting home will not be a problem. There is also
>> the tow truck!! Yucky, but still what I had to use with my ICE when the
>> timing chain broke!
>> Expecting complex electronics to solve all ones problems is INMNSHO is not a
>> direction that hobbyists need to pursue. Better to concentrate on the fun
>> stuff..
>>
>>
>> --
>> When all else fails, remember failure is the success of knowing what not to
>> do.
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>
>

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Re: range meter or ?

Stephen Chapman
In reply to this post by Stephen Chapman
I like the 30 mile round trip example.  15 miles downhill and your "range"
meter is probably indicating 60 miles left at the turnaround.  Now a mile
into the uphill section you may be indicating 5 miles left.  What good is
that?

On Thu, Jul 1, 2010 at 2:39 PM, Stephen Chapman <[hidden email]> wrote:

> Range is a function of future use.  I have a range indicator as part of the
> trip computer in my ice.  It can be easily fooled by driving habits and my
> rate of gas consumption does not really change that much.  The power used by
> an EV can easily change by a factor of 4-5.
>
>
> On Thu, Jul 1, 2010 at 2:33 PM, dave cover <[hidden email]> wrote:
>
>> But you don't use "future use." You just take the current rate of use.
>> That will go up and down as you press or release the throttle. Drive
>> harder, less range. Drive easier, more range.
>>
>> DAC
>>
>> On Thu, Jul 1, 2010 at 2:29 PM, Stephen Chapman <[hidden email]>
>> wrote:
>> > Calculating the past power used is relatively easy and relatively
>> accurate.
>> > Calculating future power use is a very nearly a shot in the dark and
>> > therefore not a good indicator of range..
>> > Stephen Chapman
>> >
>> > On Thu, Jul 1, 2010 at 2:19 PM, dave cover <[hidden email]> wrote:
>> >
>> >> Why can't a simple module take your current usage and and then
>> >> estimate range based on remaining pack capacity? If you are using X
>> >> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
>> >> of range.
>> >>
>> >> Isn't it that simple?
>> >>
>> >> DAC
>> >>
>> >>
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>>
>>
>>
>> --
>> http://www.evalbum.com/2149
>>
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Re: range meter or ?

Dave Hale
In reply to this post by dave cover-2
On Thu, Jul 1, 2010 at 11:19 AM, dave cover <[hidden email]> wrote:

> Why can't a simple module take your current usage and and then
> estimate range based on remaining pack capacity? If you are using X
> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> of range.
>
> Isn't it that simple?
>


I think it is. And accurate enough just as is the battery gauge on my
laptop. GPS? No. My laptop doesn't know that I'm going to turn up the screen
brightness and start playing a DVD. And it doesn't have to. No need to
predict the route or the future. Is the "range" provided by my laptop gauge
correct? Sure. So I start up that hill (or turn up the screen brightness)
and suddenly my range gauge changes from saying I have 15 miles (or an hour)
remaining to 5 miles (or 20 minutes) remaining. But if I turn down the
brightness or the hill levels off, then I have 10 miles (or 40 minutes)
left.

I agree with you, it's relatively simple. And it's already been done (as in
the case of laptop battery gauges,  of which mine at least is quite
accurate).

Go for it.




>
> DAC
>
> On Thu, Jul 1, 2010 at 2:08 PM, ron doctors <[hidden email]> wrote:
> > Unless the route can be programmed into the range meter system, via
> > integrated GPS unit, and all the battery parameters, plus driving/battery
> > usage history, then a range meter will be an inaccurate beast. However
> > something that says you have used 3/4 of capacity would be helpful and
> that
> > is doable.
> > My car has an old style fuel gage of the kind used in 1930's gas guzzlers
> > and I will make sure that "empty" on the gage still gives me a 1/4
> capacity.
> > Since I do not plan on anything more than being 30 miles from home, and
> my
> > friends have cell phones getting home will not be a problem. There is
> also
> > the tow truck!! Yucky, but still what I had to use with my ICE when the
> > timing chain broke!
> > Expecting complex electronics to solve all ones problems is INMNSHO is
> not a
> > direction that hobbyists need to pursue. Better to concentrate on the fun
> > stuff..
> >
> >
> > --
> > When all else fails, remember failure is the success of knowing what not
> to
> > do.
> > -------------- next part --------------
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> >
>
>
>
> --
> http://www.evalbum.com/2149
>
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Re: range meter or ?

dave cover-2
In reply to this post by Collin Kidder
> Collin Kidder <[hidden email]> wrote:
> This is as opposed to an ICE where the gas
> gauge is likely reasonably accurate.

How accurate would the gauge in an ICE be if you only had a 2 or 3
gallon fuel tank?

I think the issues are similar independent of the fuel used.

I'm not expecting it to predict the future, just a best guess based on
known facts; current use, remaining capacity. I shouldn't be
disappointed if it tells me I have X miles of range when I'm driving
mildly and then I don't get it because I started driving like a
maniac. I would be the idiot, not the gauge.

It's not a miracle device, just a driving aid. There are reasonable
devices already working in ICE's, why not in an EV. Think about the
old fuel economy gauges. They weren't much more than a vacuum gauge.
If you drove conservatively, vacuum stayed high, you would probably be
getting better gas mileage, and the gauge showed that. If you romped
on it the vacuum was low and the gauge showed that you were getting
low economy. It wasn't predicting the future, it was just showing you
a best guess based on the current conditions.

Why can't a simple device count amp hours in your pack and estimate
instantaneous remaining range based on how you are driving? Why is
this complicated?

DAC

On Thu, Jul 1, 2010 at 2:44 PM, Collin Kidder <[hidden email]> wrote:

>  Well, it's much more complicated than that. Obviously I've been on
> record as saying I don't think it has to be quite as complicated as
> other people have suggested but it's still very close.
>
> Most people still think that a "fuel" type gauge is advantageous and
> doable. A range gauge is nothing other than a fuel gauge that also tries
> to figure out how far you have to go. It can try to do this by
> calculating how far you have gone so far and extrapolate from there
> based on the current fuel gauge reading. Of course, in an EV the fuel
> gauge almost always lies. This is as opposed to an ICE where the gas
> gauge is likely reasonably accurate. This is the first big complication.
> A potential solution is to keep track of how long it takes to get to the
> 20% mark (for lithium cells. Assume I mean LiFePO4 cells when I talk
> about batteries from now on.) Once you get to 20% you look at how many
> Ah you've used. If the pack is getting weaker then this # will steadily
> go down. Unfortunately this requires one to drain the pack quite far.
> But did you ever wonder why people tell you to drain your laptop or
> cellphone battery all of the way and then recharge fully to recalibrate
> the remaining power gauge? The same thing would help to calibrate the
> fuel gauge on a lithium pack. It would have to be done periodically
> especially when it is suspected that the fuel gauge is telling lies. One
> can also try to compensate for temperature but in an EV batteries tend
> to be spread out over a large area and potentially over multiple
> locations. This makes getting temperature readings much more
> complicated. Potentially each cell should have a thermometer. In
> addition, batteries, even lithium ones, suffer from peukert factor and
> thus will not give up the same # of Ah if subjected to differing loads.
> Luckily this effect is small in lithium batteries but it still exists.
> Add that all up and the fuel gauge idea even starts to seem complicated.
> However, I think that a reasonable guess is possible. The big catch is
> that a lithium pack which hasn't been monitored closely enough could
> jump from 30-40% down to 20% all at once when the monitoring system
> detects that it got to a voltage knee.
>
> Now that the likely inaccurate fuel gauge has been covered, what about
> the distance calculation? Well, if the upcoming trip is done on the same
> sort of roads, grade, speed as the first part then the calculation will
> be very easy. It would be simple extrapolation and it would be very
> accurate. Unfortunately life doesn't always work that way. Maybe the
> first part was pretty flat and 45MPH but the upcoming part of your trip
> is very mountainous and 40MPH. This will make the calculation much more
> complicated. The range meter will think you have a lot more range than
> you really do. So what to do? Well, the range meter will have to "cheat"
> and take away range at a much faster rate than you are really traveling.
> At some point hopefully you realize that fact and adjust your plans
> accordingly. The range gauge has to trend the data to see how many amps
> you have been drawing lately in order to get a guess as to how much
> further you can go. This will necessarily jump around a bit if you
> change driving patterns.
>
> In essence, a range gauge is nothing but a very sophisticated crystal
> ball. Even a fuel gauge for an EV is really just a guess.
>
> On 7/1/2010 2:19 PM, dave cover wrote:
>> Why can't a simple module take your current usage and and then
>> estimate range based on remaining pack capacity? If you are using X
>> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
>> of range.
>>
>> Isn't it that simple?
>>
>> DAC
>>
>> On Thu, Jul 1, 2010 at 2:08 PM, ron doctors<[hidden email]>  wrote:
>>> Unless the route can be programmed into the range meter system, via
>>> integrated GPS unit, and all the battery parameters, plus driving/battery
>>> usage history, then a range meter will be an inaccurate beast. However
>>> something that says you have used 3/4 of capacity would be helpful and that
>>> is doable.
>>> My car has an old style fuel gage of the kind used in 1930's gas guzzlers
>>> and I will make sure that "empty" on the gage still gives me a 1/4 capacity.
>>> Since I do not plan on anything more than being 30 miles from home, and my
>>> friends have cell phones getting home will not be a problem. There is also
>>> the tow truck!! Yucky, but still what I had to use with my ICE when the
>>> timing chain broke!
>>> Expecting complex electronics to solve all ones problems is INMNSHO is not a
>>> direction that hobbyists need to pursue. Better to concentrate on the fun
>>> stuff..
>>>
>>>
>>> --
>>> When all else fails, remember failure is the success of knowing what not to
>>> do.
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>>
>>
>
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Re: range meter or ?

Stephen Chapman
In reply to this post by Dave Hale
Sorry, that analogy just does not work for me.  Laptop power consumption
does not frequently change by a factor of 4-5 and if the laptop powers
itself down unexpectedly, no tow truck has to be called.  :-)

All the same, if you think it will work, "more power to you".

Stephen Chapman

On Thu, Jul 1, 2010 at 3:11 PM, Dave Hale <[hidden email]> wrote:

> On Thu, Jul 1, 2010 at 11:19 AM, dave cover <[hidden email]> wrote:
>
> > Why can't a simple module take your current usage and and then
> > estimate range based on remaining pack capacity? If you are using X
> > W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> > of range.
> >
> > Isn't it that simple?
> >
>
>
> I think it is. And accurate enough just as is the battery gauge on my
> laptop. GPS? No. My laptop doesn't know that I'm going to turn up the
> screen
> brightness and start playing a DVD. And it doesn't have to. No need to
> predict the route or the future. Is the "range" provided by my laptop gauge
> correct? Sure. So I start up that hill (or turn up the screen brightness)
> and suddenly my range gauge changes from saying I have 15 miles (or an
> hour)
> remaining to 5 miles (or 20 minutes) remaining. But if I turn down the
> brightness or the hill levels off, then I have 10 miles (or 40 minutes)
> left.
>
> I agree with you, it's relatively simple. And it's already been done (as in
> the case of laptop battery gauges,  of which mine at least is quite
> accurate).
>
> Go for it.
>
>
>
>
> >
> > DAC
> >
> > On Thu, Jul 1, 2010 at 2:08 PM, ron doctors <[hidden email]> wrote:
> > > Unless the route can be programmed into the range meter system, via
> > > integrated GPS unit, and all the battery parameters, plus
> driving/battery
> > > usage history, then a range meter will be an inaccurate beast. However
> > > something that says you have used 3/4 of capacity would be helpful and
> > that
> > > is doable.
> > > My car has an old style fuel gage of the kind used in 1930's gas
> guzzlers
> > > and I will make sure that "empty" on the gage still gives me a 1/4
> > capacity.
> > > Since I do not plan on anything more than being 30 miles from home, and
> > my
> > > friends have cell phones getting home will not be a problem. There is
> > also
> > > the tow truck!! Yucky, but still what I had to use with my ICE when the
> > > timing chain broke!
> > > Expecting complex electronics to solve all ones problems is INMNSHO is
> > not a
> > > direction that hobbyists need to pursue. Better to concentrate on the
> fun
> > > stuff..
> > >
> > >
> > > --
> > > When all else fails, remember failure is the success of knowing what
> not
> > to
> > > do.
> > > -------------- next part --------------
> > > An HTML attachment was scrubbed...
> > > URL:
> >
> http://lists.sjsu.edu/mailman/private/ev/attachments/20100701/eaf6453a/attachment.html
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> > > | REPLYING: address your message to [hidden email] only.
> > > | Multiple-address or CCed messages may be rejected.
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> > >
> >
> >
> >
> > --
> > http://www.evalbum.com/2149
> >
> > _______________________________________________
> > | REPLYING: address your message to [hidden email] only.
> > | Multiple-address or CCed messages may be rejected.
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> >
> >
>
>
> --
> Dave
> http://evalbum.com/2500
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Re: range meter or ?

Stephen Chapman
In reply to this post by dave cover-2
The calculation is easy, it is the value of the answer that is in question.
The old vacuum gauges are analgous to an ampere gauge, indicating roughly
the instantaneous rate of power consumption.

If my ice trip computer only had 1 gallon of gas on which to base its
calculation, it would be totally worthless instead of only mildly
inaccurate.  One gallon of gas is roughly equivalent to the energy carried
by most EV conversions.  As it is, my trip computer gets to average its
calculation over the consumption of 15 gallons of gasoline.
Stephen Chapman

On Thu, Jul 1, 2010 at 3:20 PM, dave cover <[hidden email]> wrote:

> > Collin Kidder <[hidden email]> wrote:
> > This is as opposed to an ICE where the gas
> > gauge is likely reasonably accurate.
>
> How accurate would the gauge in an ICE be if you only had a 2 or 3
> gallon fuel tank?
>
> I think the issues are similar independent of the fuel used.
>
> I'm not expecting it to predict the future, just a best guess based on
> known facts; current use, remaining capacity. I shouldn't be
> disappointed if it tells me I have X miles of range when I'm driving
> mildly and then I don't get it because I started driving like a
> maniac. I would be the idiot, not the gauge.
>
> It's not a miracle device, just a driving aid. There are reasonable
> devices already working in ICE's, why not in an EV. Think about the
> old fuel economy gauges. They weren't much more than a vacuum gauge.
> If you drove conservatively, vacuum stayed high, you would probably be
> getting better gas mileage, and the gauge showed that. If you romped
> on it the vacuum was low and the gauge showed that you were getting
> low economy. It wasn't predicting the future, it was just showing you
> a best guess based on the current conditions.
>
> Why can't a simple device count amp hours in your pack and estimate
> instantaneous remaining range based on how you are driving? Why is
> this complicated?
>
> DAC
>
> On Thu, Jul 1, 2010 at 2:44 PM, Collin Kidder <[hidden email]> wrote:
> >  Well, it's much more complicated than that. Obviously I've been on
> > record as saying I don't think it has to be quite as complicated as
> > other people have suggested but it's still very close.
> >
> > Most people still think that a "fuel" type gauge is advantageous and
> > doable. A range gauge is nothing other than a fuel gauge that also tries
> > to figure out how far you have to go. It can try to do this by
> > calculating how far you have gone so far and extrapolate from there
> > based on the current fuel gauge reading. Of course, in an EV the fuel
> > gauge almost always lies. This is as opposed to an ICE where the gas
> > gauge is likely reasonably accurate. This is the first big complication.
> > A potential solution is to keep track of how long it takes to get to the
> > 20% mark (for lithium cells. Assume I mean LiFePO4 cells when I talk
> > about batteries from now on.) Once you get to 20% you look at how many
> > Ah you've used. If the pack is getting weaker then this # will steadily
> > go down. Unfortunately this requires one to drain the pack quite far.
> > But did you ever wonder why people tell you to drain your laptop or
> > cellphone battery all of the way and then recharge fully to recalibrate
> > the remaining power gauge? The same thing would help to calibrate the
> > fuel gauge on a lithium pack. It would have to be done periodically
> > especially when it is suspected that the fuel gauge is telling lies. One
> > can also try to compensate for temperature but in an EV batteries tend
> > to be spread out over a large area and potentially over multiple
> > locations. This makes getting temperature readings much more
> > complicated. Potentially each cell should have a thermometer. In
> > addition, batteries, even lithium ones, suffer from peukert factor and
> > thus will not give up the same # of Ah if subjected to differing loads.
> > Luckily this effect is small in lithium batteries but it still exists.
> > Add that all up and the fuel gauge idea even starts to seem complicated.
> > However, I think that a reasonable guess is possible. The big catch is
> > that a lithium pack which hasn't been monitored closely enough could
> > jump from 30-40% down to 20% all at once when the monitoring system
> > detects that it got to a voltage knee.
> >
> > Now that the likely inaccurate fuel gauge has been covered, what about
> > the distance calculation? Well, if the upcoming trip is done on the same
> > sort of roads, grade, speed as the first part then the calculation will
> > be very easy. It would be simple extrapolation and it would be very
> > accurate. Unfortunately life doesn't always work that way. Maybe the
> > first part was pretty flat and 45MPH but the upcoming part of your trip
> > is very mountainous and 40MPH. This will make the calculation much more
> > complicated. The range meter will think you have a lot more range than
> > you really do. So what to do? Well, the range meter will have to "cheat"
> > and take away range at a much faster rate than you are really traveling.
> > At some point hopefully you realize that fact and adjust your plans
> > accordingly. The range gauge has to trend the data to see how many amps
> > you have been drawing lately in order to get a guess as to how much
> > further you can go. This will necessarily jump around a bit if you
> > change driving patterns.
> >
> > In essence, a range gauge is nothing but a very sophisticated crystal
> > ball. Even a fuel gauge for an EV is really just a guess.
> >
> > On 7/1/2010 2:19 PM, dave cover wrote:
> >> Why can't a simple module take your current usage and and then
> >> estimate range based on remaining pack capacity? If you are using X
> >> W/hrs per mile and you have Y W/hrs in the pack you have about Z miles
> >> of range.
> >>
> >> Isn't it that simple?
> >>
> >> DAC
> >>
> >> On Thu, Jul 1, 2010 at 2:08 PM, ron doctors<[hidden email]>  wrote:
> >>> Unless the route can be programmed into the range meter system, via
> >>> integrated GPS unit, and all the battery parameters, plus
> driving/battery
> >>> usage history, then a range meter will be an inaccurate beast. However
> >>> something that says you have used 3/4 of capacity would be helpful and
> that
> >>> is doable.
> >>> My car has an old style fuel gage of the kind used in 1930's gas
> guzzlers
> >>> and I will make sure that "empty" on the gage still gives me a 1/4
> capacity.
> >>> Since I do not plan on anything more than being 30 miles from home, and
> my
> >>> friends have cell phones getting home will not be a problem. There is
> also
> >>> the tow truck!! Yucky, but still what I had to use with my ICE when the
> >>> timing chain broke!
> >>> Expecting complex electronics to solve all ones problems is INMNSHO is
> not a
> >>> direction that hobbyists need to pursue. Better to concentrate on the
> fun
> >>> stuff..
> >>>
> >>>
> >>> --
> >>> When all else fails, remember failure is the success of knowing what
> not to
> >>> do.
> >>> -------------- next part --------------
> >>> An HTML attachment was scrubbed...
> >>> URL:
> http://lists.sjsu.edu/mailman/private/ev/attachments/20100701/eaf6453a/attachment.html
> >>> _______________________________________________
> >>> | REPLYING: address your message to [hidden email] only.
> >>> | Multiple-address or CCed messages may be rejected.
> >>> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> >>> | OTHER HELP: http://evdl.org/help/
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> >>>
> >>
> >>
> >
> > _______________________________________________
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> >
>
>
>
> --
> http://www.evalbum.com/2149
>
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Re: range meter or ?

Collin Kidder
In reply to this post by dave cover-2
  On 7/1/2010 3:20 PM, dave cover wrote:
>> Collin Kidder<[hidden email]>  wrote:
>> This is as opposed to an ICE where the gas
>> gauge is likely reasonably accurate.
> How accurate would the gauge in an ICE be if you only had a 2 or 3
> gallon fuel tank?
Probably just as accurate. With a smaller tank you'd use something like
a smaller, more sensitive float level or something.

> I think the issues are similar independent of the fuel used.
Well, not really. Gasoline has a coefficient of expansion but it does
not change volume by as much as a battery pack can change with
temperature. Additionally, peukert factor has no liquid analog. It would
be as if stepping hard on the gas magically made some of the gasoline in
the tank "disappear" without having been burnt. And, the loss of pack
capacity doesn't have much of an analog in the gasoline realm. It's sort
of the same as if your gas tank shrank over time.


> I'm not expecting it to predict the future, just a best guess based on
> known facts; current use, remaining capacity. I shouldn't be
> disappointed if it tells me I have X miles of range when I'm driving
> mildly and then I don't get it because I started driving like a
> maniac. I would be the idiot, not the gauge.
Yes, a best guess. Like I said, it would be best if the gauge
compensated for changing conditions by slowly adjusting the estimate.
The range estimate would be based on the remaining battery power and the
average or trended amp draw. This might mean that for every mile I drive
the estimate really goes down by 5 if I'm really on the throttle.
Eventually either conditions will change or the estimate will catch up
to the usage.

> Why can't a simple device count amp hours in your pack and estimate
> instantaneous remaining range based on how you are driving? Why is
> this complicated?
>
I would not use instantaneous readings for the reasons that others have
suggested (a rollercoaster ride of values). Instead it should average
based on previous and current load. Then I'd agree. It can be done but
one should use it only as an aid and not as the gospel according to the
gauge.

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Re: range meter or ?

Collin Kidder
  On 7/1/2010 3:40 PM, Collin Kidder wrote:
>    On 7/1/2010 3:20 PM, dave cover wrote:
>>> Collin Kidder<[hidden email]>   wrote:
>>> This is as opposed to an ICE where the gas
>>> gauge is likely reasonably accurate.
>> How accurate would the gauge in an ICE be if you only had a 2 or 3
>> gallon fuel tank?
> Probably just as accurate. With a smaller tank you'd use something like
> a smaller, more sensitive float level or something.
>
Ignore what I said here... Total brain failure and I didn't quite get
what you were asking. Stephen has a good point about this. The amount of
usable energy in an EV is far lower in an EV than a normal car. An ICE
could get like 300-400 miles per fill up. This lets it average over that
span. An EV might get 30-200. I did a car that can get 100 miles on a
charge. At 100 miles over a charge it should be possible to use a range
gauge. At 30? Probably not.

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Re: range meter or ?

Rick Beebe
In reply to this post by dave cover-2
dave cover wrote:

>> Collin Kidder <[hidden email]> wrote:
>> This is as opposed to an ICE where the gas
>> gauge is likely reasonably accurate.
>
> How accurate would the gauge in an ICE be if you only had a 2 or 3
> gallon fuel tank?
>
> I think the issues are similar independent of the fuel used.
> [....]
>
> Why can't a simple device count amp hours in your pack and estimate
> instantaneous remaining range based on how you are driving? Why is
> this complicated?

I'm with you--it's not really complicated. It IS, however, a different
instrument than the ones in an ICE. As you say, we only have a 2 or 3
gallon fuel tank. The ICE gauge has a lot of built-in hysteresis. If
I've been driving conservatively and the gauge says I have 50 miles to
go and then I floor it to the top of Pike's Peak, it will take a few
minutes before the gauge reacts and drops the estimate to 20 miles. Why
not? They've built in a 30-50 mile buffer beyond "empty" so even if
they're off by a few miles you're probably not stranded on the side of
the road.

The EV gauge, on the other hand, will have to react quickly which means
the number will bounce around a lot as you drive. But I think a lot of
drivers would use that as a challenge. "It says I can go 50 miles. Let's
see if I can't make it 60." Or "It says I've got 8 miles left. If I take
Smith street it's shorter but steeper so maybe I'll take Jones. Longer
but less battery drain." Just ride with a Prius driver some time and
watch them chase the MPG graph and you'll see what I mean.

If I was building it, I would have it count amp hours and measure your
speed. Calibration would involve telling it when your pack was "full"
and when it was "empty." You can decide what those numbers are. While
driving it would look at current rate of consumption, compare that with
amp hours remaining and calculate how long you can drive at the current
rate. Multiply that by how fast you're going and you have your range. I
think I'd update the display every 5 seconds or so. Might as well
incorporate a nice little bar graph that shows the rate of consumption
too, to give people something else to look at.

It will, of course, have to be recalibrated occasionally. If I was an
OEM putting this in my cars I could have the device talk to the BMS or
other sensors to automagically adjust itself as the pack ages. But as a
DIY-installed gizmo it doesn't have to be that smart.

--Rick


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Re: range meter or ?

Roland Wiench
In reply to this post by themotorman



----- Original Message -----
From: "Dave Hale" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Thursday, July 01, 2010 12:11 PM
Subject: Re: [EVDL] range meter or ?


On Thu, Jul 1, 2010 at 11:19 AM, dave cover <[hidden email]> wrote:

Why can't a simple module take your current usage and and then
estimate range based on remaining pack capacity? If you are using X W/hrs
per mile and you have Y W/hrs in the pack you have about Z miles of range.

Isn't it that simple?

What I use as a range indicator is the past history of data that I been
driving between point A's and B's for the last 34 years, 2 months and 28
days.

I have 14 main routes that I travel and recorded daily the Date, Ambient
Temperature, Battery Temperature, Battery Initial Voltage, Battery Ending
Voltage, Battery Cycle, Distance travel, Ampere-Hour, State of Charge
Percent, Charger Amperage, Charger Voltage and Charge time.

So If I travel one route that has indicate that I will use 2.5 AH that takes
10 amps of charging in 15 minutes and another route that uses 52.5 AH which
is recharge in 63 minutes, I then will know that I can make it with a 250 AH
battery.

Roland

Roland

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Re: range meter or ?

dave cover-2
In reply to this post by Collin Kidder
> Collin Kidder <[hidden email]> wrote:
> Gasoline has a coefficient of expansion but it does
> not change volume by as much as a battery pack can change with
> temperature. Additionally, peukert factor has no liquid analog. It would
> be as if stepping hard on the gas magically made some of the gasoline in
> the tank "disappear" without having been burnt. And, the loss of pack

Not to prolong the discussion, but I think there is a correlation
here. Maybe it applies more to carburated cars than fuel injected.
But, if you romp on a gas car your mileage will go down. If you drive
conservatively, your mileage will be greater. If not, how does the
whole hypermiling thing work. The way you  drive affects how many
miles you will get to the gallon. The way you drive also affects how
many miles you can get for a given number of amphours in your pack.

On Thu, Jul 1, 2010 at 3:40 PM, Collin Kidder <[hidden email]> wrote:

>  On 7/1/2010 3:20 PM, dave cover wrote:
>>> Collin Kidder<[hidden email]>  wrote:
>>> This is as opposed to an ICE where the gas
>>> gauge is likely reasonably accurate.
>> How accurate would the gauge in an ICE be if you only had a 2 or 3
>> gallon fuel tank?
> Probably just as accurate. With a smaller tank you'd use something like
> a smaller, more sensitive float level or something.
>
>> I think the issues are similar independent of the fuel used.
> Well, not really. Gasoline has a coefficient of expansion but it does
> not change volume by as much as a battery pack can change with
> temperature. Additionally, peukert factor has no liquid analog. It would
> be as if stepping hard on the gas magically made some of the gasoline in
> the tank "disappear" without having been burnt. And, the loss of pack
> capacity doesn't have much of an analog in the gasoline realm. It's sort
> of the same as if your gas tank shrank over time.
>
>
>> I'm not expecting it to predict the future, just a best guess based on
>> known facts; current use, remaining capacity. I shouldn't be
>> disappointed if it tells me I have X miles of range when I'm driving
>> mildly and then I don't get it because I started driving like a
>> maniac. I would be the idiot, not the gauge.
> Yes, a best guess. Like I said, it would be best if the gauge
> compensated for changing conditions by slowly adjusting the estimate.
> The range estimate would be based on the remaining battery power and the
> average or trended amp draw. This might mean that for every mile I drive
> the estimate really goes down by 5 if I'm really on the throttle.
> Eventually either conditions will change or the estimate will catch up
> to the usage.
>
>> Why can't a simple device count amp hours in your pack and estimate
>> instantaneous remaining range based on how you are driving? Why is
>> this complicated?
>>
> I would not use instantaneous readings for the reasons that others have
> suggested (a rollercoaster ride of values). Instead it should average
> based on previous and current load. Then I'd agree. It can be done but
> one should use it only as an aid and not as the gospel according to the
> gauge.
>
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--
http://www.evalbum.com/2149

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Re: range meter or ?

Collin Kidder
  On 7/1/2010 4:15 PM, dave cover wrote:

>> Collin Kidder<[hidden email]>  wrote:
>> Gasoline has a coefficient of expansion but it does
>> not change volume by as much as a battery pack can change with
>> temperature. Additionally, peukert factor has no liquid analog. It would
>> be as if stepping hard on the gas magically made some of the gasoline in
>> the tank "disappear" without having been burnt. And, the loss of pack
> Not to prolong the discussion, but I think there is a correlation
> here. Maybe it applies more to carburated cars than fuel injected.
> But, if you romp on a gas car your mileage will go down. If you drive
> conservatively, your mileage will be greater. If not, how does the
> whole hypermiling thing work. The way you  drive affects how many
> miles you will get to the gallon. The way you drive also affects how
> many miles you can get for a given number of amphours in your pack.

Yes, but I'm not talking about just using more fuel. The peukert factor
is really like losing gasoline by spraying it out of the carburetor
instead of burning it. That's in ADDITION to all of the gas you are
burning. It's really that bad. This messes up the calculations for
remaining capacity. Not so much with lithium cells but it can be bad
with lead acid cells.

One might note from my long replies that I don't mind prolonging the
discussion. ;)

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