charging batteries with a low voltage source

Discussion in 'The Projects Forum' started by hornsc, Jan 9, 2009.

  1. hornsc

    Thread Starter New Member

    Jan 9, 2009
    I am trying to power a fan that draws about 4volts and 0.1A. I have a low voltage DC source of 0.5volts which isn't powerful enough even if I use a DC/DC converter. So using this I hope to charge some batteries which could then power my fan. What is the best way to do this?

    Any suggestions are much appreciated,
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    Use the converter to increase voltage to a level high enough to charge your battery. You will need some means of limiting current to avoid loading down your supply. Then all you'll need to do is wait a very long time while the battery charges.
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    As always-more questions, what current can the 1/2 V source supply? Maybe its a solar panel or thermocouple and candle? I have trouble with a 4 V converter.
  4. hornsc

    Thread Starter New Member

    Jan 9, 2009
    Thanks for replies guys, The source supply is a thermo electric generator. Across a 180 ohm resistor the TEG is outputting about 0.8 volts, so a power of around 4mW. So that implies a current of 4.4mA if my maths is correct!!
  5. Audioguru

    AAC Fanatic!

    Dec 20, 2007
    You might need to charge a battery for months at a power of only 4mW.

    When the voltage is stepped up to 4V then the current will be stepped down to only 1mA or less.