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3348Re: [solectria_ev] Re: Prius NiMH Batteries

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  • Dorothy Swann
    Dec 1, 2007
      Thanks for the math. I have not gotten around to doing that yet. I had just looked at the watt-hours per pound which was favorable. I inquired at a local surplus parts dealer, and battery packs in wrecked Priuss are available beginning at $ 400. My plan will be to acquire enough packs and build up a series/parallel combination on the bench, and start doing some load tests. The Prius pack I have seems to look at the voltage of 2 modules at a time. The voltage sampling electronics is being developed. First for 13 batteries for the Force, then for a higher number of cells.
      Bill S

      ----- Original Message ----
      From: Todd Martin <larsthelean@...>
      To: solectria_ev@yahoogroups.com
      Sent: Friday, November 30, 2007 7:47:57 AM
      Subject: [solectria_ev] Re: Prius NiMH Batteries

      Hi Bill,

      This sounds like an interesting project.

      I took the liberty of checking the specs on the Prius Nimh modules:

      Each module is 11" long by 5" wide by 3/4" thick and require a 2mm
      gap between modules for forced air cooling. They weigh 2.3 lbs and
      have 6 cells that total 7.2V at 6.5Ahr. With a standard 80% depth
      of discharge for Nimh, 5Ahr are usable.

      A Solectria Force has battery boxes that can accommodate 13 group 27
      batteries (size 12-3/4" long by 6-3/4" wide by 9-7/8" tall). This
      works out to about 1119 sq. inches of battery box floor space.

      IF you can orient the Prius Nimh modules so they the 11" long is
      vertical (not a real problem in the back box since you can always
      add a spacer between the bottom and lid if necessary, but it MAY be
      a real problem for the front box), then I figure you can fit roughly
      270 modules into a Force. This is a rough calculation without doing
      an actual layout.

      Since you will need to arrange the modules into multiple sets of
      strings of around 156V, I see the math as:
      22 modules * 7.2V = 158.4V string linked in series.
      12 strings linked in paralles * 5Ahr = 60Ahr usable.
      264 modules used total weigh 264 * 2.3 lbs = 607 lbs.

      In comparison, a Lead Acid Gel pack weighs 821 lbs. So, you will
      save 214 lbs by making the switch and increase your range from 50
      miles to approximately 60 miles.

      Provided you still have a BRUSA NLG4 (or got an NLG5) charger, I
      don't see a real problem with charging the batteries. You just need
      to find out the charging profile and set the program using the free
      DOS program. For a Zivan charger, you'd need to send it to the
      manufacturer for a re-programming.

      I agree that a BMS would be a big obstacle. Perhaps placing a
      Powercheq between each string would be enough to get by. Otherwise,
      that is a LOT of regs to be installing if you have to do every

      I'm curious as to the market rate for used Prius Nimh modules. If
      you can share the price for them, we can compare them to other
      battery choices.


      Todd Martin
      1997 Solectria Force
      VP, FVEAA

      --- In solectria_ev@ yahoogroups. com, "Bill Swann" <dbswann4@.. .>
      > I understand all the precautions you enumerate. I may purchase the
      > first of several surplus Prius battery packs tomorrow. Is there a
      > chance I can e-mail the person who put together a NiMH pack for
      the S-
      > 10. I am open to tips and tricks/opinions.
      > Thanks,Bill S
      > --- In solectria_ev@ yahoogroups. com, "Jerry Pohorsky" <Pohorsky@>
      > wrote:
      > >
      > > Howdy,
      > >
      > > The batteries in the Prius are not very suitable for the Force
      > unless you disassemble the pack, rewire the modules and come up
      > a suitable charger and BMS. NiMH batteries have a unique charging
      > profile and the standard lead acid battery chargers are not
      > appropriate. The batteries themselves are an odd physical size
      > voltage. I believe they are something like a 7.2 volt battery
      with a
      > 6.5 Amp-hour rating. That amp-hour rating is suitable for
      > intermittent duty in a hybrid but totally inadequate for an EV.
      > >
      > > You would need several strings in parallel to get the amp-hour
      > rating you need. A fellow EAA member bought several used Prius
      > on eBay and wired them in parallel for use in his US Electricar S-
      > pickup truck. He needed to invent a battery management system as
      > well as a fan-forced cooling system. The weight reduction gave
      > an improvement in acceleration over his old lead acid pack and
      > slightly more range, but eventually he got rid of them. They took
      > the entire bed of the truck. He is now running a flooded NiCad
      > that he got from a military surplus supplier. He was able to
      > the NiCads under the bed of the truck.
      > >
      > > Not all non-lead packs are series parallel combinations. I saw
      > someone selling Thunder Sky 90 Amp-Hour LiFePO4 batteries. With
      > these, you would just have a series string although there would be
      > large number of cells - they between 3 and 4 volts each.
      > >
      > > Stephen Taylor has a series string of the Valence Lithium
      > in his Force.
      > >
      > > Similarly, I have 95 Amp-hour NiMH batteries in my RAV 4 EV.
      > Unfortunately, these Panasonic batteries have been taken off the
      > market due to a lawsuit filed by Chevron - but it is another
      > where a series parallel combo was not needed.
      > >
      > > Adios,
      > >
      > > Jerry Pohorsky
      > >
      > > ----- Original Message -----
      > > From: Bill Swann
      > > To: solectria_ev@ yahoogroups. com
      > > Sent: Tuesday, November 20, 2007 6:13 PM
      > > Subject: [solectria_ev] Prius NiMH Batteries
      > >
      > >
      > > I am surprised that someone has not taken some surplus
      > from a
      > > Prius and adapted it to the Force. The energy density is
      > over
      > > lead. As it is with battery packs other that SLA, the pack
      > up
      > > being a series/parallel combination.
      > > Bill S
      > >
      > >
      > >
      > >
      > >
      > > [Non-text portions of this message have been removed]
      > >

      [Non-text portions of this message have been removed]
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