Estimating costs: Check my logic

classic Classic list List threaded Threaded
29 messages Options
12
Reply | Threaded
Open this post in threaded view
|

Estimating costs: Check my logic

Steve Kobb
Here's a cost estimate for the energy that I'll use in my 2002 S10 conversion.

Critiques and confirmations are both welcome.

*********************************************

My office is 16 miles from my home. I drive there and back 5 days a week.


It takes approximately 300 watt-hours to drive 1 mile.


300 wh per mile * 16 miles = 4800 wh

Green Mountain Energy charges me approximately $0.15 per killowatt-hour.


I have to put in a little more energy than what I take out for driving, just because of the inefficiencies of energy transfer.


4.8 * $0.15 = $0.72 * 1.1 overcharge factor = $0.792 consumed power per trip

My pack consists of twenty-six 6-volt batteries -- a total of 156 volts. Manufacturer: US Battery Model: US2000. This pack cost me $3384.


Pack capacity is 129 amp hrs at the 2-hr rate, according to a US Battery table entitled "Ampere Hour Capacity".

This table is available at http://www.usbattery.com/usb_images/USB%20Ampere%20Chart.pdf

4800 wh divided by 156 volts = 30.77 amp-hours.

30.77 ah divided by 129 ah = 23.85% DOD (Depth of Discharge).
 

23.85% DOD results in a projected longevity of 2800 cycles, according to a US Battery chart entitled "Expected Cycle Life vs. DOD".

This chart is available at http://www.usbattery.com/usb_images/cycle_life.xls.pdf

$3384 divided by 2800 cycles = $1.2086 battery cost per trip
Total energy cost of trip = $0.792 consumed power + $1.2086 battery cost = $2.00 per trip (or cycle)

$2.00 divided by 16 miles per trip = $0.125 per mile

vs.

Using mileage figures from http://www.fueleconomy.gov/:

My 1999 Infiniti gets 19 mpg city and 26 mpg highway.
I'll use 20 mpg.

16 miles divided by 20 miles per gallon = 0.8 gallon per trip

Current average local price as reported by http://www.houstongasprices.com/: $3.49 per gallon

At $3.49 per gallon, one trip has $2.792 fuel cost.
$2.792 divided by 16 miles per trip = $0.1745 per mile

Per mile cost differential: $0.0495

32 miles per day times 5 days per week times 50 weeks = 8000 miles per year
8000 times $0.0495 = $396 fuel savings per year (assuming that gas stays at $3.49).
 
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Lloyd Wayne Reece
Steve  I think your logic is good but their are a ton more costs to add
to the ICE that will really tip the balance in favor of your conversion.
Tune Up costs so many cents per mile.
Oil and Lube every 3 to 5,000 miles
Transmission check-up.
Radiator Flush
I'm just trying to remember what the Jiffy Lube guy tried to pull on me
the last time I put my car in for a simple change.
He tried to run me a $300.00 bill when all I wanted was to have him
change my transmisson fluid.

I'm sure there are more things but wear and tear on an ICE is one of the
greatest hidden costs that everybody forgets to figure in.  With all
those moving parts and computer controls you need a real expert with
expert prices sometimes to keep it all running.  At least that's what
the repair industry trys to sell.  Your electric will most likely not
have as many problems and most of the battery/cable problems you can fix
yourself in an hour and with a lot less parts costs that say oh you need
a new temp sensor or carb or distributor etc.. etc....

Lloyd Wayne Reece
1981 Lectra Centauri
Las Vegas, NV


Steve Kobb wrote:

>Here's a cost estimate for the energy that I'll use in my 2002 S10
>conversion.
>
>Critiques and confirmations are both welcome.
>
>*********************************************
>
>My office is 16 miles from my home. I drive there and back 5 days a week.
>
>
>It takes approximately 300 watt-hours to drive 1 mile.
>
>
>300 wh per mile * 16 miles = 4800 wh
>
>Green Mountain Energy charges me approximately $0.15 per killowatt-hour.
>
>
>I have to put in a little more energy than what I take out for driving, just
>because of the inefficiencies of energy transfer.
>
>
>4.8 * $0.15 = $0.72 * 1.1 overcharge factor = $0.792 consumed power per trip
>
>My pack consists of twenty-six 6-volt batteries -- a total of 156 volts.
>Manufacturer: US Battery Model: US2000. This pack cost me $3384.
>
>
>Pack capacity is 129 amp hrs at the 2-hr rate, according to a US Battery
>table entitled "Ampere Hour Capacity".
>
>This table is available at
>http://www.usbattery.com/usb_images/USB%20Ampere%20Chart.pdf
>
>4800 wh divided by 156 volts = 30.77 amp-hours.
>
>30.77 ah divided by 129 ah = 23.85% DOD (Depth of Discharge).
>
>
>23.85% DOD results in a projected longevity of 2800 cycles, according to a
>US Battery chart entitled "Expected Cycle Life vs. DOD".
>
>This chart is available at
>http://www.usbattery.com/usb_images/cycle_life.xls.pdf
>
>$3384 divided by 2800 cycles = $1.2086 battery cost per trip
>Total energy cost of trip = $0.792 consumed power + $1.2086 battery cost =
>$2.00 per trip (or cycle)
>
>$2.00 divided by 16 miles per trip = $0.125 per mile
>
>vs.
>
>Using mileage figures from http://www.fueleconomy.gov/:
>
>My 1999 Infiniti gets 19 mpg city and 26 mpg highway.
>I'll use 20 mpg.
>
>16 miles divided by 20 miles per gallon = 0.8 gallon per trip
>
>Current average local price as reported by http://www.houstongasprices.com/:
>$3.49 per gallon
>
>At $3.49 per gallon, one trip has $2.792 fuel cost.
>$2.792 divided by 16 miles per trip = $0.1745 per mile
>
>Per mile cost differential: $0.0495
>
>32 miles per day times 5 days per week times 50 weeks = 8000 miles per year
>8000 times $0.0495 = $396 fuel savings per year (assuming that gas stays at
>$3.49).
>
>
>  
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

me2-2
In reply to this post by Steve Kobb

On Wed, 2008-04-30 at 21:33 -0700, Steve Kobb wrote:
> Here's a cost estimate for the energy that I'll use in my 2002 S10
> conversion.

<snip>  Those are really interesting numbers.  I've never done the calcs
for a lead acid battery pack.

The thing that strikes me is how expensive the operating cost for the
batteries is and how shallow they have to be discharged to get that
life.  Being naive, I thought the golf car batteries (220 AH x 6Volts)
stored 1.2KWHr each.  They cost about $100, so $100/KWHr.   I never
realized how shallow they needed to be discharged.

Your numbers illustrate the truth.  $3384 for 5 KWHr (useable) is $675
per KWHr. Pretty expensive.  

Not only that, but the specific energy must be pretty low.  5 KWHr / (26
x 45lbs ea) = 9.4 watt hours per Kg, if my math is right.  

And even with the shallow discharge, the battery operating cost still
exceeds the electricity cost.  

This is where an ultra capacitor would really shine.  First, it could be
totally discharged, so its 100% usable.   Then it probably has infinite
life, so the "battery" operating cost is just about zero.

Very interesting.   Thanks for sharing.

PS: the one thing that isn't in your numbers is the aging effect of the
battery.   If you drive to work 250x a year, its going to take you a
long time to wear out your pack through charge/discharge cycles.  How
does aging play into it ?

Thanks again...

AEG.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Peter VanDerWal
In reply to this post by Steve Kobb
You've made a few mistakes:

> I have to put in a little more energy than what I take out for driving,
-snip-
> 4.8 * $0.15 = $0.72 * 1.1 overcharge factor = $0.792 consumed power per

Looks like you are assuming that charging the batteries is 90% efficient.
This is no where near accurate.
A typical charger might be about 85% efficient and batteries are about 70%
once you factor in equalization.  This makes the total charge efficiency
about 60%

So 300wh per mile / .6 = 500 wh at the outlet.
That's $0.075 per mile or $1.20 each way or $2.40 per day assuming you are
paying for the electricity when charging at work.

> Manufacturer: US Battery Model: US2000. This pack cost me $3384.
Ouch!  I think you could have got them cheaper if you bought them directly
from USBattery.  They've quoted me $2268 for 20 US125 delivered to my
door.

>4800 wh divided by 156 volts = 30.77 amp-hours.
Umm, your voltage is going to sag under load, you have to calculate for
this.  Probably will average around 146-148V while driving.
4800 wh / 147 = 32.65 AH
It's something to keep in mind, but not really significant to this
calculation

> Pack capacity is 129 amp hrs at the 2-hr rate, according to a US Battery
> table entitled "Ampere Hour Capacity".

Using the 2 hour rate is only valid if you are driving at an average speed
of 32 mph.  I.e. it takes you 30 minutes to get to work.  If it takes less
than that (higher average speed) then you should use the 1hr discharge
rate.
Again not terribly significant.

> $3384 divided by 2800 cycles = $1.2086 battery cost per trip
> Total energy cost of trip = $0.792 consumed power + $1.2086 battery cost =
> $2.00 per trip (or cycle)
>
> $2.00 divided by 16 miles per trip = $0.125 per mile

$1.20 (corrected value from above) + $1.21 = $2.41 per trip or about $0.15
per mile.
This works out to a cost savings (using your figures) of about $0.0245 per
mile.

> 8000 times $0.0495 = $396 fuel savings per year
$196 assuming you ignore the cost of maintenance on the ICE which is
typically several hundred dollars per year.

> (assuming that gas stays at $3.49).

That seems very unlikely.  My guess is that we will see a slow but steady
increase in gas prices.


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Heynow
In reply to this post by Steve Kobb
Looks good to me, but you are not including some maintenance costs that are particular to an ICE.  How about oil changes, spark plugs and wires, air filters, coolant changes, belts and hoses..etc
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Bob Bath
In reply to this post by Steve Kobb
Your logic is just fine; my short commutes mean that I
save very little as well.  However, it doesn't take
into consideration the benefits that you provide to
human health, and the planet.  Most of the time, we
only look at the bottom line that's _easier_ to
quantify.
peace,
(;-p

--- Steve Kobb <[hidden email]> wrote:

>
> Here's a cost estimate for the energy that I'll use
> in my 2002 S10
> conversion.
>
> Critiques and confirmations are both welcome.
>
> *********************************************
>
> My office is 16 miles from my home. I drive there
> and back 5 days a week.
>
>
> It takes approximately 300 watt-hours to drive 1
> mile.
>
>
> 300 wh per mile * 16 miles = 4800 wh
>
> Green Mountain Energy charges me approximately $0.15
> per killowatt-hour.
>
>
> I have to put in a little more energy than what I
> take out for driving, just
> because of the inefficiencies of energy transfer.
>
>
> 4.8 * $0.15 = $0.72 * 1.1 overcharge factor = $0.792
> consumed power per trip
>
> My pack consists of twenty-six 6-volt batteries -- a
> total of 156 volts.
> Manufacturer: US Battery Model: US2000. This pack
> cost me $3384.
>
>
> Pack capacity is 129 amp hrs at the 2-hr rate,
> according to a US Battery
> table entitled "Ampere Hour Capacity".
>
> This table is available at
>
http://www.usbattery.com/usb_images/USB%20Ampere%20Chart.pdf

>
> 4800 wh divided by 156 volts = 30.77 amp-hours.
>
> 30.77 ah divided by 129 ah = 23.85% DOD (Depth of
> Discharge).
>  
>
> 23.85% DOD results in a projected longevity of 2800
> cycles, according to a
> US Battery chart entitled "Expected Cycle Life vs.
> DOD".
>
> This chart is available at
>
http://www.usbattery.com/usb_images/cycle_life.xls.pdf

>
> $3384 divided by 2800 cycles = $1.2086 battery cost
> per trip
> Total energy cost of trip = $0.792 consumed power +
> $1.2086 battery cost =
> $2.00 per trip (or cycle)
>
> $2.00 divided by 16 miles per trip = $0.125 per mile
>
> vs.
>
> Using mileage figures from
> http://www.fueleconomy.gov/:
>
> My 1999 Infiniti gets 19 mpg city and 26 mpg
> highway.
> I'll use 20 mpg.
>
> 16 miles divided by 20 miles per gallon = 0.8 gallon
> per trip
>
> Current average local price as reported by
> http://www.houstongasprices.com/:
> $3.49 per gallon
>
> At $3.49 per gallon, one trip has $2.792 fuel cost.
> $2.792 divided by 16 miles per trip = $0.1745 per
> mile
>
> Per mile cost differential: $0.0495
>
> 32 miles per day times 5 days per week times 50
> weeks = 8000 miles per year
> 8000 times $0.0495 = $396 fuel savings per year
> (assuming that gas stays at
> $3.49).
>  
>
> --
> View this message in context:
>
http://www.nabble.com/Estimating-costs%3A-Check-my-logic-tp16992820p16992820.html
> Sent from the Electric Vehicle Discussion List
> mailing list archive at Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


Thinking about converting a gen. 5 ('92-95) Honda Civic?  My $23 "CivicWithACord" DVD (57 mins.) shows ins and outs you'll encounter, featuring a sedan; a del Sol, and a hatchback, each running 144V/18 batteries.  It focuses on component/instrumentation/battery placement and other considerations.  For more info,   http://home.budget.net/~bbath/CivicWithACord.html
                          ____
                       __/__|__\__
             =D-------/   - -     \
                      'O'-----'O'-'
Would you still drive your car if the tailpipe came out of the steering wheel?


      ____________________________________________________________________________________
Be a better friend, newshound, and
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Chad Gray-2
In reply to this post by Steve Kobb
If you are going to factor in the EV's battery life/maintenance.  Then you have to factor in the ICE's maintenance.  Oil, plugs, wires, antifreeze, parts that wear out.

You should take it out to 100,000 miles so you can compare each over a long period of time so you can get all of the maintenance involved with an ICE.

Also you say work is 16miles away, so you should be using 32 miles a day.  Unless you work a 24 hour shift.  :)


> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf Of Steve Kobb
> Sent: Thursday, May 01, 2008 12:34 AM
> To: [hidden email]
> Subject: [EVDL] Estimating costs: Check my logic
>
>
> Here's a cost estimate for the energy that I'll use in my 2002 S10
> conversion.
>
> Critiques and confirmations are both welcome.


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

gottdi
In reply to this post by Bob Bath
I agree. :  )

For me it has never been about cost but less impact.  :  )

If it were bottom line only then I'd still be driving my old VW Beetle.



On May 1, 2008, at 6:04 AM, Bob Bath wrote:

> However, it doesn't take
> into consideration the benefits that you provide to
> human health, and the planet.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
http://onegreenev.blogspot.com/
No need to wait any longer. You can now buy one off the shelf. You can still build one too.
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Matt C-2
In reply to this post by Steve Kobb
Are you going to charge at work?

If not, your DOD will be around 48% which looks like somewhere around
1200 cycles.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Chad Gray-2
I am kinda new to this.  

What is DOD, and why do the cycles drop the more you charge the battery?  I assume a cycle is the number of times a battery will take a charge before it dies.



> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf Of Matt C
> Sent: Thursday, May 01, 2008 10:27 AM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Estimating costs: Check my logic
>
> Are you going to charge at work?
>
> If not, your DOD will be around 48% which looks like somewhere around
> 1200 cycles.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev



_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Mark Grasser
In reply to this post by gottdi
You very much have to look at it from the impact perspective.

I haven't seen anyone put into the equation their time with some value
added. Makes the batteries look cheap.

Mark Grasser
 


-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of [hidden email]
Sent: Thursday, May 01, 2008 10:16 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Estimating costs: Check my logic

I agree. :  )

For me it has never been about cost but less impact.  :  )

If it were bottom line only then I'd still be driving my old VW Beetle.



On May 1, 2008, at 6:04 AM, Bob Bath wrote:

> However, it doesn't take
> into consideration the benefits that you provide to
> human health, and the planet.

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

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Roland Wiench
In reply to this post by Steve Kobb
I do not use the cost of the batteries by it self in calculating the cost
per mile.  I consider the cost of the batteries as the cost of the equipment
like the rest of the car.

Now if a person is going to change out there batteries after each drag
racing, or once a year or once every two years, because they are driving a
full discharge cycle per day or less, and you replace the battery pack that
has a life shorter than the vehicle itself, then that person may consider
the battery cost.

I lease a car, and I may change it once a year, just to get something
different.  This saves the wear and maintenance on my classic cars that I
may only drive once in a while which all of them are over 30 years old.

The amount of driving I do a day with the EV, which  may be 5 to 15 minutes
per day at a average speed of 15 mph which is all in residence areas, it
takes me a month or more to complete one discharge cycle.

I normally top off the batteries about once a week which they may be still
be above 20% DOD and charge them to only to the maximum voltage setting and
have the battery charger shut at 5% DOD.

At once a month I may take them to 0% DOD.  According to the cycle life
chart, my batteries would last me 29 years.  The last set lasted me 12
years, but I change them, because I wanted something different.

Many people replace there vehicle every 5 years, because they wanted
something different.

I think I still have some of that $0.33 a gallon gas in one of the tanks in
one of my cars which I freshen up with a pint of the new stuff about once a
year.

Distill water is now $0.59 a gallon which I use about one gallon per 100
miles.  Now, would that not be 100 miles per gallon.

Roland






----- Original Message -----
From: "Steve Kobb" <[hidden email]>
To: <[hidden email]>
Sent: Wednesday, April 30, 2008 10:33 PM
Subject: [EVDL] Estimating costs: Check my logic


>
> Here's a cost estimate for the energy that I'll use in my 2002 S10
> conversion.
>
> Critiques and confirmations are both welcome.
>
> *********************************************
>
> My office is 16 miles from my home. I drive there and back 5 days a week.
>
>
> It takes approximately 300 watt-hours to drive 1 mile.
>
>
> 300 wh per mile * 16 miles = 4800 wh
>
> Green Mountain Energy charges me approximately $0.15 per killowatt-hour.
>
>
> I have to put in a little more energy than what I take out for driving,
> just
> because of the inefficiencies of energy transfer.
>
>
> 4.8 * $0.15 = $0.72 * 1.1 overcharge factor = $0.792 consumed power per
> trip
>
> My pack consists of twenty-six 6-volt batteries -- a total of 156 volts.
> Manufacturer: US Battery Model: US2000. This pack cost me $3384.
>
>
> Pack capacity is 129 amp hrs at the 2-hr rate, according to a US Battery
> table entitled "Ampere Hour Capacity".
>
> This table is available at
> http://www.usbattery.com/usb_images/USB%20Ampere%20Chart.pdf
>
> 4800 wh divided by 156 volts = 30.77 amp-hours.
>
> 30.77 ah divided by 129 ah = 23.85% DOD (Depth of Discharge).
>
>
> 23.85% DOD results in a projected longevity of 2800 cycles, according to a
> US Battery chart entitled "Expected Cycle Life vs. DOD".
>
> This chart is available at
> http://www.usbattery.com/usb_images/cycle_life.xls.pdf
>
> $3384 divided by 2800 cycles = $1.2086 battery cost per trip
> Total energy cost of trip = $0.792 consumed power + $1.2086 battery cost =
> $2.00 per trip (or cycle)
>
> $2.00 divided by 16 miles per trip = $0.125 per mile
>
> vs.
>
> Using mileage figures from http://www.fueleconomy.gov/:
>
> My 1999 Infiniti gets 19 mpg city and 26 mpg highway.
> I'll use 20 mpg.
>
> 16 miles divided by 20 miles per gallon = 0.8 gallon per trip
>
> Current average local price as reported by
> http://www.houstongasprices.com/:
> $3.49 per gallon
>
> At $3.49 per gallon, one trip has $2.792 fuel cost.
> $2.792 divided by 16 miles per trip = $0.1745 per mile
>
> Per mile cost differential: $0.0495
>
> 32 miles per day times 5 days per week times 50 weeks = 8000 miles per
> year
> 8000 times $0.0495 = $396 fuel savings per year (assuming that gas stays
> at
> $3.49).
>
>
> --
> View this message in context:
> http://www.nabble.com/Estimating-costs%3A-Check-my-logic-tp16992820p16992820.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

joe-22
In reply to this post by gottdi
We all have different lifestyles, and different reasons for doing the EV
thing. For me, it's all about costs and the ease of maintenance; not that I
don't care about the enviroment, but that is not a big deal to me. So I
appreciate the cost analysis from Steve, or anyone else.

Joseph H. Strubhar

Web: www.gremcoinc.com

E-mail: [hidden email]
----- Original Message -----
From: <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Thursday, May 01, 2008 7:15 AM
Subject: Re: [EVDL] Estimating costs: Check my logic


>I agree. :  )
>
> For me it has never been about cost but less impact.  :  )
>
> If it were bottom line only then I'd still be driving my old VW Beetle.
>
>
>
> On May 1, 2008, at 6:04 AM, Bob Bath wrote:
>
>> However, it doesn't take
>> into consideration the benefits that you provide to
>> human health, and the planet.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>
> --
> No virus found in this incoming message.
> Checked by AVG.
> Version: 7.5.524 / Virus Database: 269.23.6/1407 - Release Date: 4/30/2008
> 11:35 AM
>
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Doug Weathers
In reply to this post by Chad Gray-2

On May 1, 2008, at 7:43 AM, Chad Gray wrote:

> What is DOD, and why do the cycles drop the more you charge the
> battery?

DoD stands for "depth of discharge".  It's a measurement (usually a
percentage) of how far you drained a battery.  To get the best life
from your lead-acid battery, you want to keep the DoD between 50% and
80% (closer to the 50% end if possible).  This means that if you design
your car for a particular range, you'll want to put twice as much
lead-acid batteries into it as required to get a good pack life.

Figuring out the DoD on the fly turns out to be a difficult problem, by
the way.  That's why EV "fuel gauges" tend to cost a lot of money -
they usually need to include data storage and a computer to do the
calculations.

> I assume a cycle is the number of times a battery will take a charge
> before it dies.

A "cycle" is shorthand for a "charge-discharge cycle".  If you charge
the battery at night, then drive it to work, that's one cycle.  If you
then charge at work, then drive home, you are putting two cycles on
your pack per workday.

Lead-acid batteries wear out a little bit each cycle.  How much depends
on several factors such as DoD, the current draw, the temperature, the
type of lead-acid battery, your charger, etc.  If you mistreat your
lead-acid batteries you might only get a few hundred cycles; if you
baby them you'll probably get several thousand cycles.  Of the
different types of lead-acid batteries available, flooded golf-cart
batteries seem to have the highest cycle life.

Other chemistries such as flooded NiCad are almost unaffected by the
number of cycles they've experienced.  We don't yet have enough data to
know for sure, but the best guess is that lithium batteries will have a
huge cycle life but may have a limited calendar life.

--
Doug Weathers
Las Cruces, NM, USA
http://www.gdunge.com/

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Andrew Kane-2
In reply to this post by Chad Gray-2
DOD = Depth of Discharge
SOC = State of Charge

     It is a characteristic of all lead-acid batteries AFAIK that
deeper discharge equates to fewer cycles. Also there is a phenomenon
called Peukert's Effect such that high rate of discharge (high amp
draw) results in less available power in the cycle.

On Thu, May 1, 2008 at 6:43 AM, Chad Gray <[hidden email]> wrote:

> I am kinda new to this.
>
>  What is DOD, and why do the cycles drop the more you charge the battery?  I assume a cycle is the number of times a battery will take a charge before it dies.
>
>
>
>
>  > -----Original Message-----
>  > From: [hidden email] [mailto:[hidden email]] On
>
>
> > Behalf Of Matt C
>  > Sent: Thursday, May 01, 2008 10:27 AM
>  > To: Electric Vehicle Discussion List
>  > Subject: Re: [EVDL] Estimating costs: Check my logic
>  >
>  > Are you going to charge at work?
>  >
>  > If not, your DOD will be around 48% which looks like somewhere around
>  > 1200 cycles.
>  >
>  > _______________________________________________
>  > For subscription options, see
>  > http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>
>  _______________________________________________
>  For subscription options, see
>  http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

John A. Evans - N0HJ
In reply to this post by Doug Weathers
Doug Weathers wrote:

> On May 1, 2008, at 7:43 AM, Chad Gray wrote:
>
>  
>> What is DOD, and why do the cycles drop the more you charge the
>> battery?
>>    
>
> DoD stands for "depth of discharge".  It's a measurement (usually a
> percentage) of how far you drained a battery.  To get the best life
> from your lead-acid battery, you want to keep the DoD between 50% and
> 80% (closer to the 50% end if possible).  
...

This is where I always get confused.  DOD is measured from the top,
correct?  i.e., If I use my battery pack just a little, my DOD could be,
say, 5% down, whereas if I consume a lot of charge, I could be at the
absolute maximum of 80% down, correct?  SOC is then 100% - DOD, correct?

thanks,
john
_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Battery Cycles

Chet Fields
In reply to this post by Doug Weathers
--- Doug Weathers <[hidden email]> wrote:
>
> On May 1, 2008, at 7:43 AM, Chad Gray wrote:
>
> A "cycle" is shorthand for a "charge-discharge cycle".  If you
> charge the battery at night, then drive it to work, that's one
> cycle. If you then charge at work, then drive home, you are
> putting two cycles on your pack per workday.

Also keep in mind that it may be better that it wasn't a complete
charge cycle (with full absorption stage) at work. If it is brought
only to about 80-90% SOC (State of charge, inverse of DOD) or the
point where most good chargers start tapering off the current this
would be a lot better on the batteries.

However, they should be fully charged at least every few days to
avoid sulfation. But multiple opportunity charges to 80-90% extend
the daily range without the extra wear on the batteries that the
full charge causes.

> Lead-acid batteries wear out a little bit each cycle.  How much
> depends
> on several factors such as DoD, the current draw, the
> temperature, the
> type of lead-acid battery, your charger, etc.  If you mistreat
> your
> lead-acid batteries you might only get a few hundred cycles; if
> you
> baby them you'll probably get several thousand cycles.  Of the
> different types of lead-acid batteries available, flooded
> golf-cart
> batteries seem to have the highest cycle life.

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Doug Weathers
In reply to this post by John A. Evans - N0HJ


John A. Evans - N0HJ wrote:

> This is where I always get confused.  DOD is measured from the top,
> correct?  i.e., If I use my battery pack just a little, my DOD could be,
> say, 5% down, whereas if I consume a lot of charge, I could be at the
> absolute maximum of 80% down, correct?  SOC is then 100% - DOD, correct?

That's the way I understand it, yes.

>
> thanks,
> john
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

--
Doug Weathers
Las Cruces, NM, USA
http://www.gdunge.com

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Chad Gray-2
In reply to this post by Doug Weathers
Thanks Doug for the excellent explanation!  Now for my fuzzy logic.  I have a feeling it is really fuzzy.  I show better performance then Steve's numbers.

So you want to have a low DOD and this will allow you to charge the pack more often, but does it give you more miles over the packs lifetime?

So according to the chart if you drain you batteries every time (DOD 100%) they will only last about 500 charges (cycles).

So if you get 50 miles for a DOD of 100% the battery pack will last 25000 miles.

If you do a DOD of 40% (40% of 50 miles is 20 miles) so 20 miles * 1475 cycles (according to the chart) = 29500 miles

If you do a DOD of 20% (20% of 50 miles is 10 miles) so 10miles * 3300 cycles (according to the chart) = 33000 miles

Say I drive to work for a year, 9-5 M-F 10 miles each way.  That is 4840 miles a year (two weeks vacation included).  
100% DOD will get me 5.2 years on a battery pack.
40% DOD will get me 6 years on a battery pack.
20% DOD will get me 6.8 years on the battery pack.

I drive about 10 miles to work so if I build something with a range of 50 miles i would want to charge at work and at night so I get the 20% DOD and 3300 cycles or 33000 miles.


Is ok for me to say that a DOD of 20% of 50 miles is 10 miles?  Do batteries discharge linearly?



> -----Original Message-----
> From: [hidden email] [mailto:[hidden email]] On
> Behalf Of Doug Weathers
> Sent: Thursday, May 01, 2008 10:56 AM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Estimating costs: Check my logic
>
>
> On May 1, 2008, at 7:43 AM, Chad Gray wrote:
>
> > What is DOD, and why do the cycles drop the more you charge the
> > battery?
>
> DoD stands for "depth of discharge".  It's a measurement (usually a
> percentage) of how far you drained a battery.  To get the best life
> from your lead-acid battery, you want to keep the DoD between 50% and
> 80% (closer to the 50% end if possible).  This means that if you design
> your car for a particular range, you'll want to put twice as much
> lead-acid batteries into it as required to get a good pack life.
>
> Figuring out the DoD on the fly turns out to be a difficult problem, by
> the way.  That's why EV "fuel gauges" tend to cost a lot of money -
> they usually need to include data storage and a computer to do the
> calculations.
>
> > I assume a cycle is the number of times a battery will take a charge
> > before it dies.
>
> A "cycle" is shorthand for a "charge-discharge cycle".  If you charge
> the battery at night, then drive it to work, that's one cycle.  If you
> then charge at work, then drive home, you are putting two cycles on
> your pack per workday.
>
> Lead-acid batteries wear out a little bit each cycle.  How much depends
> on several factors such as DoD, the current draw, the temperature, the
> type of lead-acid battery, your charger, etc.  If you mistreat your
> lead-acid batteries you might only get a few hundred cycles; if you
> baby them you'll probably get several thousand cycles.  Of the
> different types of lead-acid batteries available, flooded golf-cart
> batteries seem to have the highest cycle life.
>
> Other chemistries such as flooded NiCad are almost unaffected by the
> number of cycles they've experienced.  We don't yet have enough data to
> know for sure, but the best guess is that lithium batteries will have a
> huge cycle life but may have a limited calendar life.
>
> --
> Doug Weathers
> Las Cruces, NM, USA
> http://www.gdunge.com/
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev



_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: Estimating costs: Check my logic

Peter VanDerWal
Mathematically you have everything correct.
However, real life is a bit different.

In real life, most folks that try to push to 100% DoD on each discharge
experience FAR less than the manufacturers claimed life cycle.
There is a really simple reason for this.  The manufacturer considers the
battery worn out when it can no longer produce more than 80% of rated
capacity.
If you need 20 miles of daily range and you build an EV that has a max
100% DoD range of 20 miles, the batteries will only be able to go 16 miles
when they have 500 cycles on them (80% of 20 miles).
Uh oh, you can't make your trip anymore.  In fact after about 50-60 cycles
you will drop below 20 miles.

Second problem, as the battery approaches 100% DoD the amount of current
you can safely pull from it drops.

Third problem, and this one complicates the second problem, as the DoD
falls the batteries voltage ALSO falls.  This means that to get the same
power out of the battery you have to pull MORE current.

So as you get closer to 100% DoD the pack voltage drops, so you have to
pull more current, only less current is available. Aghh!!

Acceleration suffers, your top speed drops, you have to keep one eye on
the volt meter to make sure you don't reverse a cell, and even if you're
careful you run the risk of reversing a cell anyway.
You end up having to creep along just to get to 100% DoD.

Now consider what happens when you design the vehicle to go 20 miles while
only pulling 50% DoD.  when the batteries reach then end of their cycle
life and can only produce 80% rated capacity, you can STILL make your trip
with room to spare.
If you're really cheap, and don't mind the diminishing performance, you
can continue to use the batteries long past the end of their cycle life.
This is how many folks manage to get 10 years out of a pack of batteries.

The problem with designing a vehicle to use only 20% DoD is that you end
up carrying a LOT of extra weight in batteries.  This causes you to use
more energy for your daily commute and can have a negative impact on
handling and braking.
On the other hand, you do get lots of extra range, if you need it, and
your batteries will most likely die of old age rather then wearing out.

> Thanks Doug for the excellent explanation!  Now for my fuzzy logic.  I
> have a feeling it is really fuzzy.  I show better performance then Steve's
> numbers.
>
> So you want to have a low DOD and this will allow you to charge the pack
> more often, but does it give you more miles over the packs lifetime?
>
> So according to the chart if you drain you batteries every time (DOD 100%)
> they will only last about 500 charges (cycles).
>
> So if you get 50 miles for a DOD of 100% the battery pack will last 25000
> miles.
>
> If you do a DOD of 40% (40% of 50 miles is 20 miles) so 20 miles * 1475
> cycles (according to the chart) = 29500 miles
>
> If you do a DOD of 20% (20% of 50 miles is 10 miles) so 10miles * 3300
> cycles (according to the chart) = 33000 miles
>
> Say I drive to work for a year, 9-5 M-F 10 miles each way.  That is 4840
> miles a year (two weeks vacation included).
> 100% DOD will get me 5.2 years on a battery pack.
> 40% DOD will get me 6 years on a battery pack.
> 20% DOD will get me 6.8 years on the battery pack.
>
> I drive about 10 miles to work so if I build something with a range of 50
> miles i would want to charge at work and at night so I get the 20% DOD and
> 3300 cycles or 33000 miles.
>
>
> Is ok for me to say that a DOD of 20% of 50 miles is 10 miles?  Do
> batteries discharge linearly?
>
>
>
>> -----Original Message-----
>> From: [hidden email] [mailto:[hidden email]] On
>> Behalf Of Doug Weathers
>> Sent: Thursday, May 01, 2008 10:56 AM
>> To: Electric Vehicle Discussion List
>> Subject: Re: [EVDL] Estimating costs: Check my logic
>>
>>
>> On May 1, 2008, at 7:43 AM, Chad Gray wrote:
>>
>> > What is DOD, and why do the cycles drop the more you charge the
>> > battery?
>>
>> DoD stands for "depth of discharge".  It's a measurement (usually a
>> percentage) of how far you drained a battery.  To get the best life
>> from your lead-acid battery, you want to keep the DoD between 50% and
>> 80% (closer to the 50% end if possible).  This means that if you design
>> your car for a particular range, you'll want to put twice as much
>> lead-acid batteries into it as required to get a good pack life.
>>
>> Figuring out the DoD on the fly turns out to be a difficult problem, by
>> the way.  That's why EV "fuel gauges" tend to cost a lot of money -
>> they usually need to include data storage and a computer to do the
>> calculations.
>>
>> > I assume a cycle is the number of times a battery will take a charge
>> > before it dies.
>>
>> A "cycle" is shorthand for a "charge-discharge cycle".  If you charge
>> the battery at night, then drive it to work, that's one cycle.  If you
>> then charge at work, then drive home, you are putting two cycles on
>> your pack per workday.
>>
>> Lead-acid batteries wear out a little bit each cycle.  How much depends
>> on several factors such as DoD, the current draw, the temperature, the
>> type of lead-acid battery, your charger, etc.  If you mistreat your
>> lead-acid batteries you might only get a few hundred cycles; if you
>> baby them you'll probably get several thousand cycles.  Of the
>> different types of lead-acid batteries available, flooded golf-cart
>> batteries seem to have the highest cycle life.
>>
>> Other chemistries such as flooded NiCad are almost unaffected by the
>> number of cycles they've experienced.  We don't yet have enough data to
>> know for sure, but the best guess is that lithium batteries will have a
>> huge cycle life but may have a limited calendar life.
>>
>> --
>> Doug Weathers
>> Las Cruces, NM, USA
>> http://www.gdunge.com/
>>
>> _______________________________________________
>> For subscription options, see
>> http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
12