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7739Re: Lithium voltage sag

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  • Wolf Packs, Inc.
    Dec 7, 2011
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      > Hope to hear from a few more of the owners that have been running the 90 or 100's for awhile. Especially anyone who has some grades's to deal with.

      I climb 2,600 feet in 17 miles to get home. The first half is 1% ~ 2% uphill grade (45~50 mph speed limit) and the last half is 6% ~ 7% (I keep it between 30 and 35 mph, like most gas cars) on a very curvy road. The Force uses 32 ~ 34 amp hours to get home. I always head home with a full charge. I use Normal mode because if I switch to Power mode I will quickly sag some cells to 2.6v or less. I set my lowest cell under voltage alarm at 2.704 volts and I can quickly trip that alarm in Normal mode if I floor it.

      I had to go with Lithium because the fresh Lead pack I bought when I got the car kept going into limp mode on the last mile of the climb before getting home. I really like the Lithium pack. The car feels lighter in the turns, it easily cruises up the hill like a gas car without getting any cells below 2.8 volts. It's a lot more fun to drive without the extra 500+ pounds. Still, if I floor it on the freeway in Normal mode it would sag some cells lower than I want to go.



      > This is my major concern with all conversions. I have a friend that put all his batteries in the bed of his S-10 and come the first rain he slid into the rear end of the car in front of him - not enough weight on the front axel.



      I don't notice the front to rear weight issue when driving the curves in rain. When I hit the brakes to avoid deer, there are lots of them in these mountains, the front end drops and the car stops quickly. Perhaps the S-10 had other braking concerns like narrow or worn tires, extra weight behind the rear axle, low vacuum pressure, glazed pads, etc. I rarely drive the Force when it's snowing because of the heater draw while climbing toward home, but the few times I have it feels fine. I originally had 20 cells in the front box for weight on the front end. Last winter I changed to 8 cells in the front box and can not tell the difference. I would have all 48 in back if they would fit that way while being strapped into the 4 cell compressed bundles.

      If I were to build another Force for my wife I'd probably put in 50 of the160Ah cells. She is not as careful as I am with the accelerator pedal (coming out of the steeper turns) and she has tripped the under voltage alarm a few times.

      One suggestion for new converters: put the display where you can easily see it while driving. My display is on the cup holder below the radio and I have to look down to glance at it. I only take 1 to 2 seconds to see the voltages as they scroll to show high & low but I recently had a close call with a skunk when I looked up. In city driving it could be dangerous. It's like texting while driving´┐Ż it's a bad idea.

      Pictures at:

      http://traildog.blogspot.com/

      Paul Martin
      Ashland, Oregon

      1997 Force
      48 TS 100Ah cells (now have 7,000 miles on them)
      Hardy BMS-48
      Zivan NG3

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