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An observation with tire pressure and "MPG"

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  • sol2spirit
    Over the last few weeks (perhaps months?), my tires were starting to show their lack of pressure. So finally, I went to a gas station (!) to pump up my tires
    Message 1 of 5 , Oct 25, 2010
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      Over the last few weeks (perhaps months?), my tires were starting to show their lack of pressure.
      So finally, I went to a gas station (!) to pump up my tires over this weekend (immediately surrounded by curious "oil"ers (fellow motorists) to whom I gave a show-and-tell about the joys of electric propulsion).

      So this morning with tires fully inflated (perhaps even slightly overinflated), I was surprised by what appears to be a 15%-20% improvement in "MPGs". I normally do around 220 WHrs/mile with my Gel pack (I'm still in the process of switching over to the Thunderskys that I got - I'm just not happy with the BMS solutions available currently - but that's another story).

      Here are the specs from today (same route that I normally take):

      Ambient temperature: 60 F
      Battery temperature: 70 F
      Road condition: wet but no active rain
      No significant wind
      Driving in normal mode with high power occasionally
      Batteries: 13 Deka 8G27s
      Total miles: 3.7 miles
      Total AHr: 4.1 AHr
      170 V average (starting 172V - ending 168V)
      Total WHr: 697 WHr
      Consumption: 188 WHr / mile

      Of course, I know proper tire pressure helps mileage. However, I'm a little surprised that I should get around 15% to 20% improvement (I don't think my tire pressure previously was that bad). I will keep an eye on this and see if I can repeat this results consistenly. Moreover, I don't think most people with Gels are getting any better than 200 WHr / mile. I suspect I just got "lucky" today.

      Sol
    • Wolf
      I typically get around 288 Wh per mile in my truck on lead acid... But I am planning on upgrading it to Lithium over the winter/spring... A am planning on
      Message 2 of 5 , Oct 25, 2010
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        I typically get around 288 Wh per mile in my truck on lead acid... But I am
        planning on upgrading it to Lithium over the winter/spring...

        A am planning on building my own BMS system, since I can't find one that
        does everything I want it to do as well...

        What are the requirements you are looking for in a BMS?

        I want a nice visual digital dash board that has all the info on all the
        batteries (each cell voltage, temp, state of charge, etc...), essentially
        all the aggregate data from the battery pack in a nice graphical display
        where you can know the status of every cell in the whole pack at a glance.
        :)

        Also, since I have this nice graphical display, I also want to know
        everything about the electrical system, i.e stack voltage, current draw from
        the pack, current into each motor controller, all the status data from the
        controllers and charger, etc...

        And, I want to be able to view all the data on my smart phone... but I don't
        want to tie everything to a single opperating system like iOS, or Android,
        so I am planning on using Java Script data streaming. That way the graphical
        display can be viewed by any Wi-Fi enabled device with a web browser, (iPod
        touch, cell phone, laptop, or even an iPad) could be used as an in dash
        display.

        I was looking at using this IC for the BMS, since it is one of the few that
        is N+stackable.
        http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=bq76pl536&fileType=pdf

        And for the IEEE802.1b/g/n wireless module:
        http://www.wiznet.co.kr/UpLoad_Files/ReferenceFiles/WIZ620wi_User_Manual_V1.0.pdf


        Wolf
        *wags his tail*
        www.wolftronix.com



        On Mon, Oct 25, 2010 at 10:31 AM, sol2spirit <sol2spirit@...> wrote:

        >
        >
        >
        > Over the last few weeks (perhaps months?), my tires were starting to show
        > their lack of pressure.
        > So finally, I went to a gas station (!) to pump up my tires over this
        > weekend (immediately surrounded by curious "oil"ers (fellow motorists) to
        > whom I gave a show-and-tell about the joys of electric propulsion).
        >
        > So this morning with tires fully inflated (perhaps even slightly
        > overinflated), I was surprised by what appears to be a 15%-20% improvement
        > in "MPGs". I normally do around 220 WHrs/mile with my Gel pack (I'm still in
        > the process of switching over to the Thunderskys that I got - I'm just not
        > happy with the BMS solutions available currently - but that's another
        > story).
        >
        > Here are the specs from today (same route that I normally take):
        >
        > Ambient temperature: 60 F
        > Battery temperature: 70 F
        > Road condition: wet but no active rain
        > No significant wind
        > Driving in normal mode with high power occasionally
        > Batteries: 13 Deka 8G27s
        > Total miles: 3.7 miles
        > Total AHr: 4.1 AHr
        > 170 V average (starting 172V - ending 168V)
        > Total WHr: 697 WHr
        > Consumption: 188 WHr / mile
        >
        > Of course, I know proper tire pressure helps mileage. However, I'm a little
        > surprised that I should get around 15% to 20% improvement (I don't think my
        > tire pressure previously was that bad). I will keep an eye on this and see
        > if I can repeat this results consistenly. Moreover, I don't think most
        > people with Gels are getting any better than 200 WHr / mile. I suspect I
        > just got "lucky" today.
        >
        > Sol
        >
        >
        >


        [Non-text portions of this message have been removed]
      • sol2spirit
        On the trip back from work, I seemed to do somewhat even better... 3.8 AHr for 3.8 miles at 165V average. That means 1 AHr per mile or 165 WHr per mile (how s
        Message 3 of 5 , Oct 25, 2010
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          On the trip back from work, I seemed to do somewhat even better...
          3.8 AHr for 3.8 miles at 165V average.
          That means 1 AHr per mile or 165 WHr per mile (how's that for easy math).
          (I think my car has been possessed by aliens :-) ).
          However, I was driving carefully maximizing regen braking.
          I'll be happy with an average of 190 WHr per mile though.
          In a future trial, I'll turn off regen and see what I get then.

          The TI chip is a fine solution indeed for a BMS.

          It's similar to another chip that I've been looking at:
          http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1037,C1786,P90340

          In my experience, I find TI and Linear Tech chips to be quite robust, a little bit pricier, and a little bit more complicated to use (i.e. can require more passives and external components).

          National Semiconductor and Maxim chips tend to be easier to use but less flexible.

          I will probably put together a PCB with one of the aforementioned chips and connect it to an Atmel processor (such as that used in the Arduino system), use the Wire/Processing language (Java-based) to put together an App. In turn, I will connect that to a tablet PC (many coming out now and under $500). Should be able to design a sweet BMS/Monitoring system for quite a decent price. Have to watch out for EMF and look at where it makes sense to use digital versus analog though. SPI, I2C and other such single-ended protocols can be susceptible to EM interference. Differential CAN bus would be a much better choice.

          I also want to be able to support Gel, AGMs, or Lithiums (no reason to be chemistry specific with today's microchips). My other electric car will probably remain as AGMs for some time as I learn more about driving with lithium in the Solectria (first project).

          There is much that can be said here so perhaps it is best to start another thread on Solectria BMS design.

          -Sol

          --- In solectria_ev@yahoogroups.com, Wolf <wolf@...> wrote:
          >
          > I typically get around 288 Wh per mile in my truck on lead acid... But I am
          > planning on upgrading it to Lithium over the winter/spring...
          >
          > A am planning on building my own BMS system, since I can't find one that
          > does everything I want it to do as well...
          >
          > What are the requirements you are looking for in a BMS?
          >
          > I want a nice visual digital dash board that has all the info on all the
          > batteries (each cell voltage, temp, state of charge, etc...), essentially
          > all the aggregate data from the battery pack in a nice graphical display
          > where you can know the status of every cell in the whole pack at a glance.
          > :)
          >
          > Also, since I have this nice graphical display, I also want to know
          > everything about the electrical system, i.e stack voltage, current draw from
          > the pack, current into each motor controller, all the status data from the
          > controllers and charger, etc...
          >
          > And, I want to be able to view all the data on my smart phone... but I don't
          > want to tie everything to a single opperating system like iOS, or Android,
          > so I am planning on using Java Script data streaming. That way the graphical
          > display can be viewed by any Wi-Fi enabled device with a web browser, (iPod
          > touch, cell phone, laptop, or even an iPad) could be used as an in dash
          > display.
          >
          > I was looking at using this IC for the BMS, since it is one of the few that
          > is N+stackable.
          > http://focus.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=bq76pl536&fileType=pdf
          >
          > And for the IEEE802.1b/g/n wireless module:
          > http://www.wiznet.co.kr/UpLoad_Files/ReferenceFiles/WIZ620wi_User_Manual_V1.0.pdf
          >
          >
          > Wolf
          > *wags his tail*
          > www.wolftronix.com
          >
          >
          >
          > On Mon, Oct 25, 2010 at 10:31 AM, sol2spirit <sol2spirit@...> wrote:
          >
          > >
          > >
          > >
          > > Over the last few weeks (perhaps months?), my tires were starting to show
          > > their lack of pressure.
          > > So finally, I went to a gas station (!) to pump up my tires over this
          > > weekend (immediately surrounded by curious "oil"ers (fellow motorists) to
          > > whom I gave a show-and-tell about the joys of electric propulsion).
          > >
          > > So this morning with tires fully inflated (perhaps even slightly
          > > overinflated), I was surprised by what appears to be a 15%-20% improvement
          > > in "MPGs". I normally do around 220 WHrs/mile with my Gel pack (I'm still in
          > > the process of switching over to the Thunderskys that I got - I'm just not
          > > happy with the BMS solutions available currently - but that's another
          > > story).
          > >
          > > Here are the specs from today (same route that I normally take):
          > >
          > > Ambient temperature: 60 F
          > > Battery temperature: 70 F
          > > Road condition: wet but no active rain
          > > No significant wind
          > > Driving in normal mode with high power occasionally
          > > Batteries: 13 Deka 8G27s
          > > Total miles: 3.7 miles
          > > Total AHr: 4.1 AHr
          > > 170 V average (starting 172V - ending 168V)
          > > Total WHr: 697 WHr
          > > Consumption: 188 WHr / mile
          > >
          > > Of course, I know proper tire pressure helps mileage. However, I'm a little
          > > surprised that I should get around 15% to 20% improvement (I don't think my
          > > tire pressure previously was that bad). I will keep an eye on this and see
          > > if I can repeat this results consistenly. Moreover, I don't think most
          > > people with Gels are getting any better than 200 WHr / mile. I suspect I
          > > just got "lucky" today.
          > >
          > > Sol
          > >
          > >
          > >
          >
          >
          > [Non-text portions of this message have been removed]
          >
        • Gordon Stallings
          Here s a tip on how to manage your tire pressure: Put a set of passive pressure monitors onto your valve stems. There are several brands of these. For
          Message 4 of 5 , Oct 26, 2010
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            Here's a tip on how to manage your tire pressure:
            Put a set of passive pressure monitors onto your valve stems. There
            are several brands of these. For example, I bought a set of Tire
            Minders calibrated at 42 pounds. A quick walk around the car,
            checking for green valve caps keeps my pressures at proper levels. A
            red indicator marks a tire that needs air.

            --Gordon Stallings--

            On Oct 26, 2010, at 12:13 PM, Tom Hudson wrote:

            > It's amazing the difference tire pressure makes! I regularly check
            > the pressure on all my
            > cars (if I remember to!) and always run them at their labeled max
            > pressure. Because our
            > 2000 Honda Insight has the in-your-face fuel economy display, it's
            > really obvious there,
            > but for the Force and E-10 I reset the trip odometer on every drive
            > and mentally compute
            > the Ah/mile and if it's really out of whack, I check the inflation.
            >
            > For a good example of what the difference is, let a bunch of
            > pressure out of the tires on
            > a bicycle and ride it around a little -- you really have to work
            > harder to move.
            >
            > -Tom
            >
            > On 10/25/2010 8:31 AM, sol2spirit wrote:
            >>
            >>
            >> Over the last few weeks (perhaps months?), my tires were starting
            >> to show their lack of
            >> pressure.
            >> So finally, I went to a gas station (!) to pump up my tires over
            >> this weekend
            >> (immediately surrounded by curious "oil"ers (fellow motorists) to
            >> whom I gave a
            >> show-and-tell about the joys of electric propulsion).
            >>
            >> So this morning with tires fully inflated (perhaps even slightly
            >> overinflated), I was
            >> surprised by what appears to be a 15%-20% improvement in "MPGs". I
            >> normally do around
            >> 220 WHrs/mile with my Gel pack (I'm still in the process of
            >> switching over to the
            >> Thunderskys that I got - I'm just not happy with the BMS solutions
            >> available currently -
            >> but that's another story).
            >>
            >> Here are the specs from today (same route that I normally take):
            >>
            >> Ambient temperature: 60 F
            >> Battery temperature: 70 F
            >> Road condition: wet but no active rain
            >> No significant wind
            >> Driving in normal mode with high power occasionally
            >> Batteries: 13 Deka 8G27s
            >> Total miles: 3.7 miles
            >> Total AHr: 4.1 AHr
            >> 170 V average (starting 172V - ending 168V)
            >> Total WHr: 697 WHr
            >> Consumption: 188 WHr / mile
            >>
            >> Of course, I know proper tire pressure helps mileage. However, I'm
            >> a little surprised
            >> that I should get around 15% to 20% improvement (I don't think my
            >> tire pressure
            >> previously was that bad). I will keep an eye on this and see if I
            >> can repeat this
            >> results consistenly. Moreover, I don't think most people with Gels
            >> are getting any
            >> better than 200 WHr / mile. I suspect I just got "lucky" today.
            >>
            >> Sol
            >>
            >>
            >
            > --
            > Thomas Hudson
            > http://portev.org -- Electric Vehicles, Solar Power& More
            > http://klanky.com -- Animation Projects
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >
            >
            >
          • Tom Hudson
            It s amazing the difference tire pressure makes! I regularly check the pressure on all my cars (if I remember to!) and always run them at their labeled max
            Message 5 of 5 , Oct 26, 2010
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              It's amazing the difference tire pressure makes! I regularly check the pressure on all my
              cars (if I remember to!) and always run them at their labeled max pressure. Because our
              2000 Honda Insight has the in-your-face fuel economy display, it's really obvious there,
              but for the Force and E-10 I reset the trip odometer on every drive and mentally compute
              the Ah/mile and if it's really out of whack, I check the inflation.

              For a good example of what the difference is, let a bunch of pressure out of the tires on
              a bicycle and ride it around a little -- you really have to work harder to move.

              -Tom

              On 10/25/2010 8:31 AM, sol2spirit wrote:
              >
              >
              > Over the last few weeks (perhaps months?), my tires were starting to show their lack of
              > pressure.
              > So finally, I went to a gas station (!) to pump up my tires over this weekend
              > (immediately surrounded by curious "oil"ers (fellow motorists) to whom I gave a
              > show-and-tell about the joys of electric propulsion).
              >
              > So this morning with tires fully inflated (perhaps even slightly overinflated), I was
              > surprised by what appears to be a 15%-20% improvement in "MPGs". I normally do around
              > 220 WHrs/mile with my Gel pack (I'm still in the process of switching over to the
              > Thunderskys that I got - I'm just not happy with the BMS solutions available currently -
              > but that's another story).
              >
              > Here are the specs from today (same route that I normally take):
              >
              > Ambient temperature: 60 F
              > Battery temperature: 70 F
              > Road condition: wet but no active rain
              > No significant wind
              > Driving in normal mode with high power occasionally
              > Batteries: 13 Deka 8G27s
              > Total miles: 3.7 miles
              > Total AHr: 4.1 AHr
              > 170 V average (starting 172V - ending 168V)
              > Total WHr: 697 WHr
              > Consumption: 188 WHr / mile
              >
              > Of course, I know proper tire pressure helps mileage. However, I'm a little surprised
              > that I should get around 15% to 20% improvement (I don't think my tire pressure
              > previously was that bad). I will keep an eye on this and see if I can repeat this
              > results consistenly. Moreover, I don't think most people with Gels are getting any
              > better than 200 WHr / mile. I suspect I just got "lucky" today.
              >
              > Sol
              >
              >

              --
              Thomas Hudson
              http://portev.org -- Electric Vehicles, Solar Power& More
              http://klanky.com -- Animation Projects



              [Non-text portions of this message have been removed]
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