Solar Circuits with Battery Back ups

Discussion in 'The Projects Forum' started by Collin Porter, Feb 10, 2015.

  1. Collin Porter

    Thread Starter New Member

    Feb 10, 2015

    So I've just started this new project and i'm looking for some help. I have a solar panel [5 watts (12 volts, 0.4 amps)] I'm using this solar panel to power two 120mm PC fans [2.5 watts(12 volts, 0.2 amps)] however I'm trying to incorporate a battery back up, so that the fans will blow even when the solar panel is not receiving light(night).

    would it be as simple as running a diode between the solar panel and the battery array? so electricity could flow from the solar panel to the battery but not from the battery to the solar panel?

    For my battery array I have several re-chargeable AAA batteries (1.5V, 900 mAh) how many should I use? i would need to connect 8 in parallel to get up 12 volts? how about in series?

  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
    Connect the 1.5v batteries in series to get 12v, a diode in series with the solar panel will prevent the batteries feeding backwards, can you post a diagram?
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    The SP is way under rated to supply a 5 W load; nothing left to charge batte0ry.
    How many hours per day are fans to operate?
    Figure on enough battery capacity to run fans for a full day cycle; then figure SP capacity to charge battery & supply fans.
    A 5 W SP will give about 2 W average , measured from 9 AM to 4 PM, April, 2009, non tracking.