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Range question

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  • umarc@arios.to
    Today I made a 27-mile trip in my Force using 35 amp-hours (13.5 miles each way). Arriving home I noticed that even though I d started with a full charge, the
    Message 1 of 5 , Feb 4, 2001
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      Today I made a 27-mile trip in my Force using 35 amp-hours (13.5 miles
      each way). Arriving home I noticed that even though I'd started with a
      full charge, the car had lost much of its power and was unable to
      maintain speed on the last two hills. I was frankly surprised -- my
      batteries are brand new Interstate SRM-27's, which I believe hold 80
      amp-hours; why am I losing power after only 35? The effective range of
      the car appears to be less than 30 miles, despite the new batteries.

      I live in Massachusetts, and the temperature was about 30 degrees
      today. I had to leave the car outside at my destination for about 8
      hours; could that have had something to do with it?

      This was not highway driving, incidentally; I did the whole trip on
      city streets, never exceeding 40 mph the whole way.

      Another factor to consider is that my charger is behaving strangely;
      if left running it will charge the car to about +2 amp hours and then
      stop. If unplugged and allowed to sit for an hour or so, then plugged
      in again, it will charge the car to about -2. The manual says I should
      charge to -4, but I can't easily get the charger to do that. It's a
      Solectria BC-1000, by the way, and the car is a 1992 Force (that is to
      say, it was built from a 1992 Geo Metro and the manual supplied with
      it is for a 1992 Force).

      Any ideas?

      Rob Landry
      umarc@...
    • David Roden (Akron OH USA)
      ... You have part of the answer already -- cold temperature. Batteries like it at about 80 deg F, and lose capacity with each degree below that point. (I
      Message 2 of 5 , Feb 4, 2001
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        On 5 Feb 2001, at 5:52, umarc@... wrote:

        > I was frankly surprised -- my
        > batteries are brand new Interstate SRM-27's, which I believe hold 80
        > amp-hours; why am I losing power after only 35? The effective range of the
        > car appears to be less than 30 miles, despite the new batteries.

        You have part of the answer already -- cold temperature. Batteries like
        it at about 80 deg F, and lose capacity with each degree below that
        point. (I used to have the formula, but I've forgotten it.)

        The second part is a reality of batteries. That amp-hour rating you
        quote is the 20-hour rate -- meaning that your 80 amp hour batteries will
        deliver 80 amp hours only when those amp hours are withdrawn over a
        period of 20 hours (that is, at 4 amps). This is much less than the
        current you use when driving. The higher the current, the fewer the amp-
        hours you can use before the battery is effectively discharged. (And
        that amp-hour capacity is most likely rated at 80 deg F, too.)

        To get a better idea of how much capacity you ~really~ have, look at the
        battery's 75 amp reserve capacity. It will usually be rated in minutes.
        You may have to contact Interstate to get it, though, because published
        specs for marine batteries are usually at the 25-amp rate, a bit low for
        realistic ratings in EV use.

        A typical good-quality marine battery, the Trojan 27TMH, is rated 51
        minutes at 75 amps (60/51*75 = 64 amp hours). The East Penn 8G27, which
        Solectria recommends (or at least did last time I spoke with them) has
        even lower reserve capacity, 40 minutes at 75 amps (50 amp hours).

        Finally, remember that your range is set by the weakest battery in the
        pack. When it goes dead, its high internal resistance drags down the
        voltage (and it can be damaged by cell reversal). So if you have even
        one battery that isn't 100% up to par, even though it's new, that will
        limit your range, too.

        To fix your range problem, I would start by trying to keep the batteries
        warm. Fit the battery boxes with as much styrofoam insulation as you can
        squeeze in around them. This will help retain heat of driving and
        charging. If that's not enough, you might want to buy Solectria's
        battery thermal management system (or make your own).

        You should be able to get 40-50 miles of range in moderately warm
        weather, but I'm not surprised that you're getting only 30 or so at 30
        deg F. At that temperature, that's actually not bad.

        > Another factor to consider is that my charger is behaving strangely;
        > if left running it will charge the car to about +2 amp hours and then
        > stop. If unplugged and allowed to sit for an hour or so, then plugged
        > in again, it will charge the car to about -2.

        Your Interstate batteries are flooded type, no? Your charger may be set
        up for gel batteries. They are normally charged to a lower finish
        voltage than flooded types. You may need to send the charger to
        Solectria to be reprogrammed.


        David Roden - Akron, Ohio, USA
        1991 Solectria Force 144vac
        1991 Ford Escort Green/EV 128vdc
        1979 General Engines ElectroPed 24vdc
        1974 Honda Civic EV 96vdc
        1970 GE Elec-trak E15 36vdc
        = = = = = = = = = = = = = = = = = = = = = = = = = = =
        NOTE: If you receive an email which exhorts you to "Send
        this to everyone you know," you don't know me.
        = = = = = = = = = = = = = = = = = = = = = = = = = = =
      • Tracy, Matt
        Original message fragment: I live in Massachusetts, and the temperature was about 30 degrees today. I had to leave the car outside at my destination for about
        Message 3 of 5 , Feb 5, 2001
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          Original message fragment:
          I live in Massachusetts, and the temperature was about 30 degrees today. I
          had to leave the car outside at my destination for about 8 hours; could that
          have had something to do with it?

          ----------
          My response:
          Couple thoughts about temperature. The batteries generate heat as they
          discharge, and as they charge. As they get older, they generate more than
          when they were new. Outside certain temperatures (high or low) you need to
          treat them carefully, including leaving them alone until they get back
          inside specifications. I replaced the charger in my '92 Force with a Zivan
          NG3, which has an optional temperature probe. It modifies the voltage as
          temperature changes, and shuts off charging if the temperature exceeds 120
          degrees Fahrenheit.

          I bought a couple indoor/outdoor digital thermometers, and placed the
          "outdoor" probes on the flooded cell batteries - one for the front 4, and
          one for the back 8 - and put the displays on the carpet in front of the
          emergency brake. I made a pocket with tape and stuck it on one of the
          interior batteries in each pack - I put the charger's temperature probe in
          the back pocket. As my batteries have matured, they don't have much trouble
          staying between 80 and 100 degrees, even when it's cold. When they were
          younger, I used the 1/2" insulation that is designed to go under sleeping
          bags. It is cheap, and easy to cut to size.

          My point, temperature measurement is cheap, batteries are expensive, measure
          the temperature and treat your batteries accordingly, especially if your
          charger does not automatically compensate for temperature.

          Matt Tracy
        • william glickman
          Sounds like your battery pack cooled off in those 8 hours and lost a normal amount of capacity for that temperature. ...
          Message 4 of 5 , Feb 5, 2001
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            Sounds like your battery pack cooled off in those 8 hours and lost a
            normal amount of capacity for that temperature.

            On Mon, 05 Feb 2001 05:52:20 -0000 umarc@... writes:
            > Today I made a 27-mile trip in my Force using 35 amp-hours (13.5
            > miles
            > each way). Arriving home I noticed that even though I'd started with
            > a
            > full charge, the car had lost much of its power and was unable to
            > maintain speed on the last two hills. I was frankly surprised -- my
            > batteries are brand new Interstate SRM-27's, which I believe hold 80
            > amp-hours; why am I losing power after only 35? The effective range
            > of
            > the car appears to be less than 30 miles, despite the new batteries.
            >
            > I live in Massachusetts, and the temperature was about 30 degrees
            > today. I had to leave the car outside at my destination for about 8
            > hours; could that have had something to do with it?
            >
            > This was not highway driving, incidentally; I did the whole trip on
            > city streets, never exceeding 40 mph the whole way.
            >
            > Another factor to consider is that my charger is behaving strangely;
            > if left running it will charge the car to about +2 amp hours and
            > then
            > stop. If unplugged and allowed to sit for an hour or so, then
            > plugged
            > in again, it will charge the car to about -2. The manual says I
            > should
            > charge to -4, but I can't easily get the charger to do that. It's a
            > Solectria BC-1000, by the way, and the car is a 1992 Force (that is
            > to
            > say, it was built from a 1992 Geo Metro and the manual supplied with
            > it is for a 1992 Force).
            >
            > Any ideas?
            >
            > Rob Landry
            > umarc@...
            >
            >
            >
            > ------------------------ Yahoo! Groups Sponsor
            >
            > To unsubscribe from this group, send an email to:
            > force_ev-unsubscribe@egroups.com
            >
            >
            >

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          • william glickman
            Sounds like your battery pack cooled off in those 8 hours and lost a normal amount of capacity for that temperature. ...
            Message 5 of 5 , Feb 5, 2001
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              Sounds like your battery pack cooled off in those 8 hours and lost a
              normal amount of capacity for that temperature.

              On Mon, 05 Feb 2001 05:52:20 -0000 umarc@... writes:
              > Today I made a 27-mile trip in my Force using 35 amp-hours (13.5
              > miles
              > each way). Arriving home I noticed that even though I'd started with
              > a
              > full charge, the car had lost much of its power and was unable to
              > maintain speed on the last two hills. I was frankly surprised -- my
              > batteries are brand new Interstate SRM-27's, which I believe hold 80
              > amp-hours; why am I losing power after only 35? The effective range
              > of
              > the car appears to be less than 30 miles, despite the new batteries.
              >
              > I live in Massachusetts, and the temperature was about 30 degrees
              > today. I had to leave the car outside at my destination for about 8
              > hours; could that have had something to do with it?
              >
              > This was not highway driving, incidentally; I did the whole trip on
              > city streets, never exceeding 40 mph the whole way.
              >
              > Another factor to consider is that my charger is behaving strangely;
              > if left running it will charge the car to about +2 amp hours and
              > then
              > stop. If unplugged and allowed to sit for an hour or so, then
              > plugged
              > in again, it will charge the car to about -2. The manual says I
              > should
              > charge to -4, but I can't easily get the charger to do that. It's a
              > Solectria BC-1000, by the way, and the car is a 1992 Force (that is
              > to
              > say, it was built from a 1992 Geo Metro and the manual supplied with
              > it is for a 1992 Force).
              >
              > Any ideas?
              >
              > Rob Landry
              > umarc@...
              >
              >
              >
              > ------------------------ Yahoo! Groups Sponsor
              >
              > To unsubscribe from this group, send an email to:
              > force_ev-unsubscribe@egroups.com
              >
              >
              >

              ________________________________________________________________
              GET INTERNET ACCESS FROM JUNO!
              Juno offers FREE or PREMIUM Internet access for less!
              Join Juno today! For your FREE software, visit:
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