Solar Panel to Charge Lithium Polymer Batteries

Discussion in 'The Projects Forum' started by zenite, Jan 22, 2010.

  1. zenite

    Thread Starter New Member

    Dec 21, 2009
    15
    0
    I am using lithium polymer batteries for my TEC and am planning to include solar panels to power the thing up.

    The battery I am using...http://shop.singahobby.com/?q=node/19204

    This is the specs for the solar panel I am using,

    • [SIZE=-1]Operating Voltage: 15.4 V[/SIZE][SIZE=-1]
      [*][SIZE=-1]Operating Current: 100 mA[/SIZE][SIZE=-1]
      [*][SIZE=-1]Typical Voc: 19 V[/SIZE][SIZE=-1]
      [*][SIZE=-1]Typical Isc : 120 mA[/SIZE][/SIZE][/SIZE][/SIZE]
    Is the panel able to charge the battery or will it instead drain its power? Also, do I need a charge controller to charge the battery. I am actually pretty clueless as to how to hook up the panel, battery charger and the battery itself. Could appreciate it if someone points me in the right direction.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312

    A diode will only allow electron flow in one direction, so you would use diodes to keep the batteries from draining into the solar cells. Think about night, Your panel would charge batteries during the day, but at night, the batteries would drain back into the panel without diodes.

    As for charge controllers, you want to read the data sheet for the battery you are using. Batteries typically need more than one voltage throughout charging. There is a bulk voltage charge, a top-off charge, and a float charge. (These can vary for different types of battery construction. ie: lead-acid, Li-Ion, NiCad, ...)

    If you kept pumping 14v into a 12v battery after it was full, you would overcharge the battery with resulting fire, acid leaks, or lower battery life. The charger/controller will measure the battery to know what it needs, and when.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    At 100mA charge = 44h to charge, full charge detection verry difficult; a timer would not know starting state of charge,could over charge, temperature change would never happen. Outlook -bleak.
     
  5. DC_Kid

    Distinguished Member

    Feb 25, 2008
    638
    9
    the only way to charge a battery is to have a charge voltage above battery voltage. its really a game of current control. charging 12v battery with 14v and a resistor will charge the battery. car battery is 12v, but when the car is running the voltage on the bat is ~14.4v so current (charge) flows into the battery, thus adding energy to the battery chemistry, etc.....

    a 12v battery that has no capacity can read 12v on a volt meter.
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    True. I should have chosen my words (numbers) better. What I was getting at was, Overcharging a battery, not giving a 12v battery 14v to charge it.

    After the charge cycle should have ended, continual higher voltage will result in problems with battery. By that I mean voltage over float.

    I gotta but my head in gear before I put my mouth(or hands) in gear.
     
  7. zenite

    Thread Starter New Member

    Dec 21, 2009
    15
    0
    So the charge controller is to prevent overcharging. Can I then connect the terminals of the solar panel to the power input of the charger for the lithium polymer battery, that is, using the LiPo charger as the charge controller since it performs the same function?

    I am also looking into better solar panel, 100mA is definately too small. Is it possible to connect 2 panels in parallel to give 200mA?
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Connect panels in parallel if they are of the same voltage. I just bought a Harbor Freight 45W panel,3 15W panels in parallel.' had a coupon for US $ 159 +tax. Had to check if diodes were in panel or controller- in controller-2 in parallel. My guess would to have a diode for ea panel, but under a load they all even out.
     
  9. thatguitarguy

    New Member

    Jan 27, 2010
    2
    0
    I have the same Harbor Freight setup to charge a a couple of deep cycle batteries for my RV. Is the box a controller or just a regulator? Are you saying that the "controller" contains diodes to prevent draining of the battery? I haven't opened mine up, and wouldn't be sure what I was looking at if I did. I have been manually attaching and detaching the setup to prevent overcharging and back-draining into the panel, but if there are diodes in place I think I could just keep an eye out for over charging and not worry about the system when it gets dark. Am I on the right track?

    Do I need to get a small PWM controller, say 10 or 20amp, or will the included "controller" take care of my needs?

    Thanks for your help.
     
  10. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    The H. Ft. controller is for lead-acid 12V battery, with low V cutoff @ 11V, high V
    disconnect @ 14V, not a real smart controller. Will plot output of panel when the sun comes back out- and this is Tucson.
     
  11. thatguitarguy

    New Member

    Jan 27, 2010
    2
    0
    Do the HF panels or controller have blocking diodes or just the 11V cutoff?

    Lately, even when the sun shines here on Colorado it's been really cold.
     
  12. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,170
    395
    Blocking diodes are built into controller which removes load from battery below 11V, disconnects panel above 14V-- I think. No tests yet, cloudy again today.
     
Loading...