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RE: [FT897] solar charging

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  • Larry P Thomas
    I have always wondered if solar cell of say 50-60watt range could be used to power the Yaesu charger directly without any solar cell controller between the
    Message 1 of 5 , Jun 3, 2005
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      I have always wondered if solar cell of say 50-60watt range could be used to
      power the Yaesu charger directly without any solar cell controller between
      the solar cell and the charger. I have not tried it yet but I am thinking
      it may work just fine in spite of the potential for higher solar cell
      voltage as the battery becomes fully charged.

      The reason I think this is that inside the Yaesu charger for the FT-897
      batteries is a +12v to +24v switching power supply prior to reaching the
      actual battery charge control circuit. The normal input to this charger for
      AC use comes from a +24v wall wart type power supply. The internal switcher
      allows operation from a vehicle battery system at a nominal voltage of
      13.8-14.5 voltage. Voltage in a vehicle can even run higher if the battery
      in the vehicle is going bad or become disconnected while running. Since this
      voltage is converted to +24v by a switcher type power supply and the
      switcher should operate properly as long as the input voltage to the
      switcher is never higher than the designed output voltage I think it should
      work. I don't think a +12v solar cell would have an open circuit terminal
      voltage that would exceed +24v. If this was a possibility a simple low power
      circuit could clamp solar cell voltage to no more than +24v. I say low
      power because the solar cell, if designed for a nominal +12v system, should
      not be able to deliver much power at +24v level. Open circuit is basically
      a no load situation. In other words, the system should be self limiting.

      I hope to try this if the weather ever gets better and the sun comes out
      again here in Kansas. I am hoping the switcher's boost configuration will
      act as an efficient solar cell controller. If it proves useful, I will buy
      a second charger and run both inputs from the same solar cell for field day
      usages. Even if it does not work as expected I'm sure a simple modification
      to the +12v to +24v switchers will work.

      Ideally, and I've been working on this, the best solution would be to be
      able to sense which battery is in use at any given time (without having to
      perform any hardware modification to the radio) and switch a single Yaesu
      charge to the unused battery for charging or topping off. I am currently
      looking a monitoring, via the rear access to battery voltage, such things as
      impedance of the battery an any circuitry attached to various signal
      frequencies (concept: battery in use should show a much lower impedance),
      noise on battery terminals (concept: battery in use may have more noise
      energy, high frequency, low frequency or even just fluxuations than the
      battery that is just floating) Note it is the battery in use or not in use
      I am looking to find, not the battery most in need of charging. Once this
      is determined, a box would switch the charger between battery A or B. With
      this setup I could run a battery down and switch knowing that the battery I
      just left would begin charging via the solar cell.

      Just some thoughts I wanted to share to see if anybody else had any ideas or
      was working on something similar.

      73's Larry P. Thomas, wa0gwa

      Imagine it/Achieve it --- Dream it/Become it
      Larry P. Thomas, wa0gwa 1 913 244-8761
      Krell Technologies (http://www.krell.com)
      8960 Bond, Overland Park, KS 66214-1722 USA

      -----Original Message-----
      From: FT897@yahoogroups.com [mailto:FT897@yahoogroups.com] On Behalf Of
      Darrell Koranda
      Sent: Thursday, June 02, 2005 8:46 PM
      To: FT897@yahoogroups.com
      Subject: RE: [FT897] solar charging

      Use either a voltage regulator on the solar panel or a string of silicon
      diodes. These can be arranged on a rotatable switch to set voltage to the
      battery. Each diode will drop .6 volt DC, monitor voltage with a meter.
      Some solar panels can get as high as 21 Volt DC open circuit and can destroy

      what is behind them. I know, I destroyed a 12 volt thermoelectric
      refrigerator by connecting straight to my 100 watt panel. Darrell KB4XJ
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