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550Re: [force_ev] Battery conditioners, monitors and solar...

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  • David Roden (Akron OH USA)
    Jul 1, 2002
      On 1 Jul 2002 at 16:09, Andrew Foss wrote:

      > Has anyone and experience or opinions about battery conditioners, so
      > called "de-sulfators"?

      All the tests I've seen are anecdotal. A battery electrochemist will tell you
      that there is no scientific basis to their "theory" -- there is no resonance in a
      battery at any of the frequencies they use. Besides, most ordinary cheap
      hardware-store battery chargers pulse, too.

      Some people report good results from "desulfators," but I'm not convinced
      that they couldn't get exactly the same results by using a battery charger in
      exactly the same way.

      > My Solectria Ammeter just broke and it's back in MA. getting fixed, but
      > I'm also wondering about using the Emeter Link 10 or Trimetric?

      These are used in many EVs. The disadvantage of the Emeter over the
      Solectria / Brusa AH counter is that it's primarily an RE product and not
      really designed for EVs. It requires a special external isolated power supply
      and, in most cases, a prescaler. This increases the price.

      The Emeter's advantage is that it has more built in smarts than the older
      Solectria / Brusa product (the current Brusa meter is fairly comparable). The
      Emeter also can handle higher currents with the prescaler, but this is not
      really important for unmodified Solectria cars.

      Bottom line is that it should work fine.

      > It sounds like SLA batteries can be continuously trickle
      > charged w/o a charging controller if the current is less than 1.5% of
      > the amphour rating.

      Don't believe it. A charger that never shuts off will kill any battery, especially
      the gel batteries usually used in Solectrias.

      As a rule of thumb, the smarter the charge controller (and the more it costs
      <g>), the lower the amoritized cost of your batteries. If you want still better
      service life and range, look into controlling charge at the individual module
      level. (Charge control at the cell level would be even better, but it's
      impractical with the sealed valve regulated modules Solectria use.)

      > I've done some quick math on using the Unisolar flexible solar panels,
      > which are so popular on boats. The hood, roof and trunk of the force
      > would support 13 11 watt panels. Each panel can deliver an average of
      > 2.6 amphours/day(average 5.1 solar hours at SF latititude). Across 13
      > panels with 70% battery efficiency that's 23 amphours/day or nearly 20
      > miles/day. It's far from being truly self-sustaining, but these panels
      > are reasonably inexpensive now I wonder if it would be good to help
      > reduce the deep cycle discharge a bit, keep the batteries individually
      > and more evenly trickle charged and even in a real pinch 2-3 days in the
      > full sun and you can be fully recharged? Any way it would just feel good
      > to be able to carry some free charging cabability on board!

      Not to throw water on the idea, but PV panels are usually rated best-case.
      The surface of a car is not optimum for orienting them toward the sun, unless
      you tilt the car to face the sun as the earth rotates <g>. Do the figures you
      quoted include this deviation from optimum?

      Don't forget that attaching the panels to the car will adversely affect the car's
      aerodynamic qualities, reducing its efficiency.

      PVs might improve battery life by reducing the amount of time they spend in
      a discharged state. However, you could accomplish the same thing by
      plugging in at work.

      I think Tom Hudson has the most practical approach to a solar-powered EV.
      He put the PVs on his house, not his car. He mounted enough of them to
      offset the car's energy use, and bought a grid-intertie inverter. While he's
      away at work, the PVs on the house are stuffing electricity into the grid.
      When he comes home he plugs the car in and sucks it back out --
      essentially using the power grid as a very large battery that never wears out.

      David Roden
      Akron OH USA
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