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Re: Current Draw at Different Speeds

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  • otedawg
    Geo, I m not sure how I missed this... Right now, I don t have anything that keeps my pack from over-discharging, at all. I ve got a cleanpower miniBMS
    Message 1 of 22 , Mar 15, 2013
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      Geo,
      I'm not sure how I missed this...
      Right now, I don't have anything that keeps my pack from over-discharging, at all. I've got a cleanpower miniBMS installed, and I'm still kicking myself for not installing an eLithion instead. I'd love to get the individual cell voltages out of my pack.

      My BMS is only for monitoring. I'd like to know if one cell decides to go bad or if I'm lowering the voltage below the BMS defined minimum.

      I don't see much of a way to do what you're thinking of unless you're prepared to part with a few (4ish) watts per hour...

      My original thought would be a NO relay feeding a HV contactor tied into the input of the DCDC, with the control signal coming from the eLithion's Low Battery Line. (really, the relay isn't needed, but I take you to be more paranoid than me. :P)

      BUT, there's a simpler way that doesn't waste as much power.

      Just simply tying a HV Solid state relay would accomplish your purpose. You could use the same Low Battery Line to drive the relay. Something like this would be perfect.
      http://www.digikey.com/product-detail/en/D2D12/CC1041-ND/139556

      I may do this once I upgrade to a eLithion.

      Josh



      --- In solectria_ev@yahoogroups.com, "geo_homsy2" <geo.homsy@...> wrote:
      >
      > Hi Otedawg-
      >
      > since you seem to be one of the few besides myself who still believes in BMS's...
      >
      > How do you prevent the DC-DC converter from over-discharging your pack? I have no such protection. I've wired the discharge-ok signal from my eLithion to the drive-disable input on the solectria ignition box, so the drive will cut out if there are any low cells in the pack.
      >
      > My fear is, of course, doing something like leaving the headlights on and leaving for a one week vacation, or something stupid like that.
      >
      > //Geo
      >
      >
      > --- In solectria_ev@yahoogroups.com, "otedawg" <joshua.orfield@> wrote:
      > >
      > > I just did a drive yesterday in my 96 Force with 156V 100AH CALB Lithiums - pushed it to (the BMS's) limit, drove 49.8Mi, average speed 40 mph, used 73.27 Ah (counter on the dash), and got 1.47 Ah/Mile.
      > >
      > > My Force does have an AC24 and DMOC445 in it.
      > >
      > > 0-60: 12sec
      > > Cruise: 54 Mph (above that, and vibrations get loud)
      > > Top Speed: 74 Mph (Top Speed I've had it to - From my math, that's theoretical as well 13,000RPM)
      > >
      > > Thanks,
      > > Otedawg
      > >
      > > --- In solectria_ev@yahoogroups.com, "Bob" <r.strattan@> wrote:
      > > >
      > > >
      > > >
      > > >
      > > >
      > > >
      > > > For my '97 Force with 156 volt East Penn 8G27 lead acid batteries, a rough rule of thumb is 1 amp per mph at steady speed, level, no wind on good pavement. Thus 35 A @ 35 mph, 50 A @ 50 mph, 60 A @ 60 mph, etc.
      > > >
      > > > If you do the math that is equivalent to 1 amp*hour per mile. In reality I rarely get better than 1.2 A*H/mile overall average for a trip.
      > > >
      > > > You may want to increase the estimate accordingly to your experience. This is consistant with assuming that the road load is all rolling friction resistance, no aerodynamic drag, which is a reasonablly good assumption for urban driving. The aero drag component of current (proportional to force, torque) increases as the square of the speed and becomes dominant at high speeds, but won't have much effect below 50 mph.
      > > >
      > > > Bob Strattan
      > > > Tulsa, OK
      > > >
      > > > --- In solectria_ev@yahoogroups.com, "Michael" wrote:
      > > > >
      > > > > I'm looking for some info on current draw for a Force.
      > > > > How many amps does a Force draw driving on level ground, steady speed at 35 mph, 50 mph and 60 mph and specify the voltage you are running.
      > > > > Thanks,
      > > > > Michael Conn
      > > > >
      > > >
      > >
      >
    • geo_homsy2
      Hi Josh- your proposal, sadly, won t work. I wish it would. The traction pack supplies the DC-DC, which supplies the ignition switch, which supplies the BMS,
      Message 2 of 22 , Mar 28, 2013
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        Hi Josh-

        your proposal, sadly, won't work. I wish it would. The traction pack supplies the DC-DC, which supplies the ignition switch, which supplies the BMS, which asserts the "charge OK" and/or "discharge OK" signals.

        If one tries to use the BMS to cut off the HV input to the DC-DC, then once you turn off the ignition, the BMS is no longer powered, hence the DC-DC is no longer powered, hence no more power to the ignition switch, hence you can never switch the car on again.

        One common method is to have a small additional 12 volt cell, for activating the BMS initially. I've been trying to avoid this.

        Still lookin'... :)

        And yeah, I'm paranoid. Don't want to zorch 7000 bucks worth of batteries by leaving my headlights on. This is a high-stakes game...

        //Geo

        --- In solectria_ev@yahoogroups.com, "otedawg" <joshua.orfield@...> wrote:
        >
        > Geo,
        > I'm not sure how I missed this...
        > Right now, I don't have anything that keeps my pack from over-discharging, at all. I've got a cleanpower miniBMS installed, and I'm still kicking myself for not installing an eLithion instead. I'd love to get the individual cell voltages out of my pack.
        >
        > My BMS is only for monitoring. I'd like to know if one cell decides to go bad or if I'm lowering the voltage below the BMS defined minimum.
        >
        > I don't see much of a way to do what you're thinking of unless you're prepared to part with a few (4ish) watts per hour...
        >
        > My original thought would be a NO relay feeding a HV contactor tied into the input of the DCDC, with the control signal coming from the eLithion's Low Battery Line. (really, the relay isn't needed, but I take you to be more paranoid than me. :P)
        >
        > BUT, there's a simpler way that doesn't waste as much power.
        >
        > Just simply tying a HV Solid state relay would accomplish your purpose. You could use the same Low Battery Line to drive the relay. Something like this would be perfect.
        > http://www.digikey.com/product-detail/en/D2D12/CC1041-ND/139556
        >
        > I may do this once I upgrade to a eLithion.
        >
        > Josh
        >
        >
        >
        > --- In solectria_ev@yahoogroups.com, "geo_homsy2" <geo.homsy@> wrote:
        > >
        > > Hi Otedawg-
        > >
        > > since you seem to be one of the few besides myself who still believes in BMS's...
        > >
        > > How do you prevent the DC-DC converter from over-discharging your pack? I have no such protection. I've wired the discharge-ok signal from my eLithion to the drive-disable input on the solectria ignition box, so the drive will cut out if there are any low cells in the pack.
        > >
        > > My fear is, of course, doing something like leaving the headlights on and leaving for a one week vacation, or something stupid like that.
        > >
        > > //Geo
        > >
        > >
        > > --- In solectria_ev@yahoogroups.com, "otedawg" <joshua.orfield@> wrote:
        > > >
        > > > I just did a drive yesterday in my 96 Force with 156V 100AH CALB Lithiums - pushed it to (the BMS's) limit, drove 49.8Mi, average speed 40 mph, used 73.27 Ah (counter on the dash), and got 1.47 Ah/Mile.
        > > >
        > > > My Force does have an AC24 and DMOC445 in it.
        > > >
        > > > 0-60: 12sec
        > > > Cruise: 54 Mph (above that, and vibrations get loud)
        > > > Top Speed: 74 Mph (Top Speed I've had it to - From my math, that's theoretical as well 13,000RPM)
        > > >
        > > > Thanks,
        > > > Otedawg
        > > >
        > > > --- In solectria_ev@yahoogroups.com, "Bob" <r.strattan@> wrote:
        > > > >
        > > > >
        > > > >
        > > > >
        > > > >
        > > > >
        > > > > For my '97 Force with 156 volt East Penn 8G27 lead acid batteries, a rough rule of thumb is 1 amp per mph at steady speed, level, no wind on good pavement. Thus 35 A @ 35 mph, 50 A @ 50 mph, 60 A @ 60 mph, etc.
        > > > >
        > > > > If you do the math that is equivalent to 1 amp*hour per mile. In reality I rarely get better than 1.2 A*H/mile overall average for a trip.
        > > > >
        > > > > You may want to increase the estimate accordingly to your experience. This is consistant with assuming that the road load is all rolling friction resistance, no aerodynamic drag, which is a reasonablly good assumption for urban driving. The aero drag component of current (proportional to force, torque) increases as the square of the speed and becomes dominant at high speeds, but won't have much effect below 50 mph.
        > > > >
        > > > > Bob Strattan
        > > > > Tulsa, OK
        > > > >
        > > > > --- In solectria_ev@yahoogroups.com, "Michael" wrote:
        > > > > >
        > > > > > I'm looking for some info on current draw for a Force.
        > > > > > How many amps does a Force draw driving on level ground, steady speed at 35 mph, 50 mph and 60 mph and specify the voltage you are running.
        > > > > > Thanks,
        > > > > > Michael Conn
        > > > > >
        > > > >
        > > >
        > >
        >
      • otedawg
        Geo, I was assuming that you would be plugged into the wall, which I now see isn t a good assumption. The Elithion does supply 12V... It seems like this would
        Message 3 of 22 , Mar 29, 2013
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          Geo,
          I was assuming that you would be plugged into the wall, which I now see isn't a good assumption. The Elithion does supply 12V...

          It seems like this would have to be done at the controller or the BMS level. Somehow closing a switch based on the SOC of the HV pack should be possible.

          Now that I think about it, if you wanted to spend more cash you could do it - just add another DC-DC, an arduino /uC with a relay shield, some sort of opto-isolated HV probe for the arduino, and the solid state switch.

          Again, I would think that this should be done at the BMS level.

          This way you could disable the input to the main DC-DC based on a voltage level of the HV pack.

          I'd just say don't leave the headlights on. :P

          -Josh

          --- In solectria_ev@yahoogroups.com, "geo_homsy2" <geo.homsy@...> wrote:
          >
          > Hi Josh-
          >
          > your proposal, sadly, won't work. I wish it would. The traction pack supplies the DC-DC, which supplies the ignition switch, which supplies the BMS, which asserts the "charge OK" and/or "discharge OK" signals.
          >
          > If one tries to use the BMS to cut off the HV input to the DC-DC, then once you turn off the ignition, the BMS is no longer powered, hence the DC-DC is no longer powered, hence no more power to the ignition switch, hence you can never switch the car on again.
          >
          > One common method is to have a small additional 12 volt cell, for activating the BMS initially. I've been trying to avoid this.
          >
          > Still lookin'... :)
          >
          > And yeah, I'm paranoid. Don't want to zorch 7000 bucks worth of batteries by leaving my headlights on. This is a high-stakes game...
          >
          > //Geo
          >
          > --- In solectria_ev@yahoogroups.com, "otedawg" <joshua.orfield@> wrote:
          > >
          > > Geo,
          > > I'm not sure how I missed this...
          > > Right now, I don't have anything that keeps my pack from over-discharging, at all. I've got a cleanpower miniBMS installed, and I'm still kicking myself for not installing an eLithion instead. I'd love to get the individual cell voltages out of my pack.
          > >
          > > My BMS is only for monitoring. I'd like to know if one cell decides to go bad or if I'm lowering the voltage below the BMS defined minimum.
          > >
          > > I don't see much of a way to do what you're thinking of unless you're prepared to part with a few (4ish) watts per hour...
          > >
          > > My original thought would be a NO relay feeding a HV contactor tied into the input of the DCDC, with the control signal coming from the eLithion's Low Battery Line. (really, the relay isn't needed, but I take you to be more paranoid than me. :P)
          > >
          > > BUT, there's a simpler way that doesn't waste as much power.
          > >
          > > Just simply tying a HV Solid state relay would accomplish your purpose. You could use the same Low Battery Line to drive the relay. Something like this would be perfect.
          > > http://www.digikey.com/product-detail/en/D2D12/CC1041-ND/139556
          > >
          > > I may do this once I upgrade to a eLithion.
          > >
          > > Josh
          > >
          > >
          > >
          > > --- In solectria_ev@yahoogroups.com, "geo_homsy2" <geo.homsy@> wrote:
          > > >
          > > > Hi Otedawg-
          > > >
          > > > since you seem to be one of the few besides myself who still believes in BMS's...
          > > >
          > > > How do you prevent the DC-DC converter from over-discharging your pack? I have no such protection. I've wired the discharge-ok signal from my eLithion to the drive-disable input on the solectria ignition box, so the drive will cut out if there are any low cells in the pack.
          > > >
          > > > My fear is, of course, doing something like leaving the headlights on and leaving for a one week vacation, or something stupid like that.
          > > >
          > > > //Geo
          > > >
          > > >
          > > > --- In solectria_ev@yahoogroups.com, "otedawg" <joshua.orfield@> wrote:
          > > > >
          > > > > I just did a drive yesterday in my 96 Force with 156V 100AH CALB Lithiums - pushed it to (the BMS's) limit, drove 49.8Mi, average speed 40 mph, used 73.27 Ah (counter on the dash), and got 1.47 Ah/Mile.
          > > > >
          > > > > My Force does have an AC24 and DMOC445 in it.
          > > > >
          > > > > 0-60: 12sec
          > > > > Cruise: 54 Mph (above that, and vibrations get loud)
          > > > > Top Speed: 74 Mph (Top Speed I've had it to - From my math, that's theoretical as well 13,000RPM)
          > > > >
          > > > > Thanks,
          > > > > Otedawg
          > > > >
          > > > > --- In solectria_ev@yahoogroups.com, "Bob" <r.strattan@> wrote:
          > > > > >
          > > > > >
          > > > > >
          > > > > >
          > > > > >
          > > > > >
          > > > > > For my '97 Force with 156 volt East Penn 8G27 lead acid batteries, a rough rule of thumb is 1 amp per mph at steady speed, level, no wind on good pavement. Thus 35 A @ 35 mph, 50 A @ 50 mph, 60 A @ 60 mph, etc.
          > > > > >
          > > > > > If you do the math that is equivalent to 1 amp*hour per mile. In reality I rarely get better than 1.2 A*H/mile overall average for a trip.
          > > > > >
          > > > > > You may want to increase the estimate accordingly to your experience. This is consistant with assuming that the road load is all rolling friction resistance, no aerodynamic drag, which is a reasonablly good assumption for urban driving. The aero drag component of current (proportional to force, torque) increases as the square of the speed and becomes dominant at high speeds, but won't have much effect below 50 mph.
          > > > > >
          > > > > > Bob Strattan
          > > > > > Tulsa, OK
          > > > > >
          > > > > > --- In solectria_ev@yahoogroups.com, "Michael" wrote:
          > > > > > >
          > > > > > > I'm looking for some info on current draw for a Force.
          > > > > > > How many amps does a Force draw driving on level ground, steady speed at 35 mph, 50 mph and 60 mph and specify the voltage you are running.
          > > > > > > Thanks,
          > > > > > > Michael Conn
          > > > > > >
          > > > > >
          > > > >
          > > >
          > >
          >
        • janzicek
          Hello all, I know this is an old thread... but I just saw it the other day when someone else posted something on it. About a year ago I put half of a volt
          Message 4 of 22 , Jan 24
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            Hello all, I know this is an old thread... but I just saw it the other day when someone else posted something on it.  About a year ago I put half of a volt pack in my solectria (running 200V at top of charge).  I too used the elithion BMS and wanted a separation of the traction and DC/DC converter power.  So I built a simple analog UVLO circuit to put inline with the DC/DC converter HV feed.  See attached photos.  If anyone is interested I can share the schematic etc...   The circuit works great, I have put quite a few miles on it and luckily I have never activated the UVLO, but I did test it to make sure it's effective.


            In the photos see album titled "UVLO circuit...." it is potted in SilGuard because it is installed underhood.  The scope plot shows input v and output v.  Output is the one that cuts in and cuts out based on input voltage.  It also has some hysteresis to prevent oscillation.  The circuit is installed in the positive power line of the DC/DC input.


            Cheers,

            Josh

          • paul dove
            yes, I would like to see the schematic if you can find it.
            Message 5 of 22 , Jan 24
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              yes, I would like to see the schematic if you can find it.

              --- In solectria_ev@yahoogroups.com, <josh@...> wrote:
              >
              > Hello all, I know this is an old thread... but I just saw it the other day when someone else posted something on it. About a year ago I put half of a volt pack in my solectria (running 200V at top of charge). I too used the elithion BMS and wanted a separation of the traction and DC/DC converter power. So I built a simple analog UVLO circuit to put inline with the DC/DC converter HV feed. See attached photos. If anyone is interested I can share the schematic etc... The circuit works great, I have put quite a few miles on it and luckily I have never activated the UVLO, but I did test it to make sure it's effective.
              >
              >
              > In the photos see album titled "UVLO circuit...." it is potted in SilGuard because it is installed underhood. The scope plot shows input v and output v. Output is the one that cuts in and cuts out based on input voltage. It also has some hysteresis to prevent oscillation. The circuit is installed in the positive power line of the DC/DC input.
              >
              >
              > Cheers,
              > Josh
              >
            • janzicek
              I have added the schematic and a simulation result to the photos folder. Please review and ask any questions that come to mind. Cheers, Josh
              Message 6 of 22 , Jan 24
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                I have added the schematic and a simulation result to the photos folder.  Please review and ask any questions that come to mind.


                Cheers,

                Josh

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