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Re: [solectria_ev] Update on ca100's

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  • paul dove
    Same goes for charging. Not a lot to gain by trying to get them all fully charged by balancing circuits. It damages cells for very little gain.
    Message 1 of 14 , Jul 7, 2013
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      Same goes for charging. Not a lot to gain by trying to get them all fully charged by balancing circuits. It damages cells for very little gain.




      ________________________________
      From: "theoldcars@..." <theoldcars@...>
      To: solectria_ev@yahoogroups.com
      Sent: Friday, June 7, 2013 8:24 PM
      Subject: Re: [solectria_ev] Update on ca100's



       
      CALB low voltage limit under load is 2.5 volts. There is not a lot of
      capacity between 2.5 and 3.0 volts so its a heavy price to pay for little gain.

      Don Blazer


      In a message dated 6/6/2013 9:12:39 P.M. Pacific Daylight Time,
      cbliss@... writes:

      First, I drive with a BMS, that said; The 2.78 is an acceptable limit to
      hit and get home. Generally speaking, permanent damage happens around 2.5.
      I have seen a number of cells do a slow bleed to below that without damage,
      but under load, 2.5 is about it. Because I have a BMS, I charge to 3.6 and
      balance to 3.45. Anything over 3.4 should be fully charged and then the
      will settle to 3.35(ish).

      The beauty of my bms is that it reports high and low cells so I know, real
      time, exactly what the batteries are up to, standing or under load.

      Your results sound great.

      From: _solectria_ev@yahoogroups.com_ (mailto:solectria_ev@yahoogroups.com)
      [mailto:_solectria_ev@yahoogroups.com_
      (mailto:solectria_ev@yahoogroups.com) ] On
      Behalf Of russell_fauver
      Sent: Thursday, June 06, 2013 8:48 PM
      To: _solectria_ev@yahoogroups.com_ (mailto:solectria_ev@yahoogroups.com)
      Subject: [solectria_ev] Update on ca100's

      Been taking it easy on the batteries since I don't have a BMS. I'm only
      charging to 189.6 volts. How did I pick that number? Well, from cycling
      them
      on the bench 3.4v seemed like they were full and the voltage would climb
      rapidly after that. I set the charger to 19o.4 which is 3.4 per cell and
      it's the float voltage according to Calb. Then I let it charge. As it
      approached full I started measuring each cell and just when the first of
      them started to climb above 3.40 I noted the charge voltage and used that
      as
      the max setting, 189.6v

      Cycling on the bench taught me a lot about the batts. I found that sitting
      over night after a full charge they would settle down to 3.34v so I set
      187.1 as the float voltage. I also learned that cell voltage drops off
      sharply while discharging after 3.00v so I thought I'd use 168 as a minimum
      pack voltage. One thing I messed up on when cycling them was I let one cell
      get way too low, down to 1.0v. Thought I ruined it. After cycling it, it
      seemed like it would be ok but with a slightly lower capacity than the rest
      of 'em. When tested against others it seemed to hold about 110ah and stay
      with the others down to 3.0v but it's voltage would drop off first. I
      marked
      it with a sharpie and put it in the trunk with the others.

      For the first few drives I only used about 40-60ah but I knew if I wanted
      to
      go for a full discharge charge run I would have to watch the cell that I
      damaged. I connected a fused wire to each terminal of that cell and ran 'em
      up between the seats where I could check it with a voltmeter from time to
      time. This week I had family in town and they all wanted a ride in The
      Force. Wanting to show them that it is an acceptable 2nd car I drove it
      like
      an ICE car. 55mph on country roads, up and down hills with 4 adults and the
      AC blowing cold air. After 50 miles they were suitably impressed. I was too
      :-) I drove it to work a couple times and my wife and I drove around a bit
      this evening to use up a little more power while monitoring that weak cell.
      We were about 3/4 of a mile from home when the voltage showed 2.78 at
      40mph
      and would climb back to 3.05 when coasting without regen. Parked the car in
      the driveway at 110.08ah and 93.5 miles. Weak cell voltage was 3.00 and
      pack
      voltage was 169.9v. With a more conservative foot and just me and my wife
      in
      the car I think it'll easily exceed 100 miles per charge.

      With this kind of range it should be easy to 'keep it between the knees'
      :-)

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