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Re: [HARC] Nicad Charging

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  • john seidelman
    Best thing to do ,is get another battery pack,Dc adapter for you car,aa battery holder,you can put batteries in.Hope that helps you. John wd8bwk ... From:
    Message 1 of 2 , Jun 25, 2002
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      Best thing to do ,is get another battery pack,Dc adapter for you car,aa battery holder,you can put batteries in.Hope that helps you. John wd8bwk
      ----- Original Message -----
      From: johnwehm
      Sent: Tuesday, June 25, 2002 4:17 PM
      Subject: [HARC] Nicad Charging

      Is there a nicad expert out there?  I have a tendency to want to
      ALWAYS run the battery down and then FULLY charge it up.  My HT
      requires that the batter be plugged into the radio when charging. 
      That means that I can not use my HT for 16 hours!

      How often should I let the battery run down and fully charge and is
      it ok the partially charge the battery and then use the radio for a
      while?

      John Wehmer
      WB9JSR/8
      Port Sheleon



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    • scott.a.hansen@jci.com
      Hi John, I am not an expert, but I have done a fair amount of research in this area for my boys RC car racing so I will share what little I know about the
      Message 2 of 2 , Jun 26, 2002
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        Hi John,
        I am not an expert, but I have done a fair amount of research in this area
        for my boys RC car racing so I will share what little I know about the
        subject.
        Nicads love to be worked pretty hard. The very light duty use we give them
        in our HT's is not enough to keep them happy. They should be periodically
        discharged to keep them at there best. The experts on this subject tell us
        not to fully discharge the pack. It's not good to pull the pack below .6
        volts per cell. That means that a 12 volt pack needs to have 10 cells in
        it to get the voltage required (1.2 volts per cell), so that pack should
        not be discharged below 6 volts.

        The reason is that all the cells will not discharge evenly and discharging
        below the .6 volt limit could cause the weakest cell to be completely dead
        and the remaining cells to still have a charge. Further discharging will
        cause the dead battery to see a reverse voltage/current. This is called
        cell reversal. I guess that's not good for them.

        All that said, I have more than 20 packs for RC car racing ranging from $20
        to $80 each so I am a bit leery of taking chances with the packs. It is
        common practice to completlly discharge. I discharge my cells completely!
        I have experimented with storing the cells completely shorted, but I could
        not see any performance increase by doing this, so I just store them dead.

        The best thing to do is to build a discharger. I build mine using
        automotive light bulbs. I can add or subtract bulbs as needed.
        Establishing the discharge rate will require a bit of experimenting. You
        want the pack to get a little bit warm during discharge. (110F or so) If
        it's not getting warm, it is not working hard enough. However, you don't
        want it to get hot!

        Heat given off during discharge is OK.

        Never charge a hot battery. Let it come to room temp or even colder. (I
        put them in a cooler on race day to allow faster charging. Probably not
        necessary of an HT battery)

        Never let a nicad get hot during charging, this is a sign of over charging.
        The reaction taking place in the cells during charging is actually
        endothermic. When the cell reaches full charge, the reaction changes to
        exothermic and the cell gives off oxygen (bad) and heat (also bad)

        Don't let the battery sit on the charger. This causes the formation of a
        crystal structure called a dendrite. The dendrites puncture the dielectric
        in the cell and cause miniature shorts. This obviously shortens the life
        of the battery.

        Is not good for a nicad to be stored for long periods of time fully
        charged. The battery will eventually discharge itself while sitting there.
        This dramatically shortens battery life. Always store (long term) your
        nicads dead! They come from the factory dead!

        Resist the temptation to "top off" the pack This also promotes dendrite
        growth and shortens the life. Allow the pack to discharge to the .6 volt
        per cell level before recharging. (if the radio will work at that low of a
        level)

        Now for the big question, How often to discharge the pack? Good question,
        If you could do it once a month, that would be great. That's a lot of
        maintenance. You should shoot for every other month to be safe. Just put
        the pack on the discharger and let it go dead. Once the pack is cool, let
        it charge back up fully and you are in business.

        I was able to do a lot of experimenting and research while racing. There
        is a lot of good info available on the web, but be sure of your source. The
        military and NASA are great sources.

        I hope this helps.
        73
        Scott
        AB8JS





        johnw@netonecom.
        net To: k8daa@yahoogroups.com
        cc:
        06/25/02 04:17 Subject: [HARC] Nicad Charging
        PM
        Please respond
        to k8daa






        Is there a nicad expert out there? I have a tendency to want to
        ALWAYS run the battery down and then FULLY charge it up. My HT
        requires that the batter be plugged into the radio when charging.
        That means that I can not use my HT for 16 hours!

        How often should I let the battery run down and fully charge and is
        it ok the partially charge the battery and then use the radio for a
        while?

        John Wehmer
        WB9JSR/8
        Port Sheleon




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