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Tx battery question

Discussion in 'General Discussion' started by Monte55, Apr 29, 2014.

  1. Monte55

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    Will using alkaline cells which run at about 1.6 volts new give better rf output than rechargeable cells that are only about 1.35 charged.
     
  2. usaken

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    Though the NIMH voltage is lower, their amp hour rating is much higher
     
  3. Monte55

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    Well, that may be true. I wonder what the alkaline cell voltage drops to when under load. Do you have any idea what the mah of a good alkaline cell is?
    As long as the alkaline voltage does not drop too much under load, I feel it would put out more power ...maybe for not as long though as hi mah rechargables.
    Example....if I connected a 12 volt bulb to a large car battery that was run down to 11 volts, it would be dimmer than the same bulb connected to a much smaller battery with less ah capacity running at a full 12 volts as long as the load was not so great that it pulled the voltage down
     
  4. SilentAV8R

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    In general the RF output power of the transmitter is not really affected by the battery voltage. As long as there is sufficient voltage t operate the TX you'll see about the same voltage until you get really low near total depletion of the cells.
     
  5. npalen

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    You guys aroused my curiosity so I checked alkaline voltage with transmitter off at 5.72 VDC and turned on at 5.52 VDC.
     
  6. SilentAV8R

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    No surprise there. Loaded voltage is always lower than unloaded voltage. The TX pulls about 80 mA so that is not an unexpected voltage drop. These cells typically have a slightly higher Internal Resistance (IR) which increases the voltage depression under load.

    But real world, while the voltage is dropping across the entire discharge of the cells, the TX power output remains essentially the same. Yes, it will drop a bit near the end of the cell charge, but it is not like it gets cut in half or anything like that.

    Here is a spec sheet for one brand:

    http://data.energizer.com/PDFs/E91.pdf
     
  7. npalen

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    Interesting stuff! Thanks for posting.
     
  8. Monte55

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    I put in 4 freshly charged 2300 ma cells. Total volts with tx off 5.52 v.......tx on 5.43 v. 134 ma draw. I thought the draw was supposed to be less than 100 ma.