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Prius NiMH Ovonics Batteries

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  • theoldcars@aol.com
    Hello Mike Thanks for taking the time to post your results with the Prius packs. Sorry to say I would have been surprised if it was much different. About six
    Message 1 of 1 , Dec 25, 2007
      Hello Mike

      Thanks for taking the time to post your results with the Prius packs. Sorry
      to say I would have been surprised if it was much different.

      About six months ago Noel was putting a pack of Ovonics in. Anyone know how
      he is doing with them?

      Don Blazer

      In a message dated 12/25/2007 9:03:13 A.M. Pacific Standard Time,
      mikep_95133@... writes:

      There are a few directions to approach the Prius packs for use in an EV.

      Energy content is about 1.0-1.2 kwhrs per pack from the testing that I
      did. Five in parallel give you 5.0-6.0 kwhrs of energy. That might get
      you 20-25 miles of range if you drain the pack dead. I'm assuming 250
      watt-hours per mile. Following the rule of thumb to not go lower than
      50% state of charge, you might have a range of 10-12 miles. Imagine
      having this kind of range after spending the time it takes to
      mechanically restrain every module so they don't expand and wiring it
      all up. A 1 amp charge rate will ruin an unrestrained Prius module.
      Then there is how to charge nimh in parallel. Some say it's
      impossible. Ask them how many times they have tried it. It can be done
      but requires even more of a complicated pack. The built in relays in
      the Prius packs make parallel charging and it's associated maintenance
      possible. Every now and then the pack needs to be separated into
      individual packs and charged separately.

      Then there is the cooling issue. That's an entire page all by itself.

      The Prius modules are rated to last 150k miles because they do in fact
      run in a narrow band of soc. I forget the exact number, if I ever knew
      it, but guessing at 40-80% is pretty close. That tight band is how
      they get millions of very shallow charge/discharge cycles. In an EV
      one hopes to get to 1000 cycles. The plates that make up each module
      are just thinner looking to me, than say the EV95 in the RAV4/Ranger
      nimh cells. That relates to being more efficient at accepting
      regen energy. Not all batteries are good at taking short dumps of
      energy and actually converting it chemically and storing it as
      electrical energy. Some of it is absorbed and turned into heat instead.

      Having several packs in Parallel will help distribute the load. But
      you only get a very short range for all of your work. I can tell you
      that having 5 Prius packs in parallel gave me the lowest pack
      impedance I will ever have. My regen was so severe it would almost
      break the rear tires lose on deceleration.

      Anyway, it sure is fun to tell your friends that your EV drives on
      Prius batteries. Unless the EV is something light like a golf cart, I
      suspect the lifetime will be short. If nothing else the range is just
      not worth the effort, to me anyway. I started to figure this out after
      spending weeks making up fan control circuits and lots of testing.

      The guy I sold all of my perfectly good packs to, smoked several of
      them right off the bat. I can promise you he is much more educated
      than I am. A professor in fact. The bottom line is that these
      different versions of nimh batteries, Cobasys, Prius, Sanyo, are so
      different in chacteristics that each should be considered a completely
      different chemistry.

      Here is a pic of the packs in the bed of my truck. There are more in
      that folder.



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