Solar Systems and Battery Banks

Discussion in 'The Projects Forum' started by pathfind2003, Jun 22, 2008.

  1. pathfind2003

    Thread Starter New Member

    Jun 22, 2008
    OK, I have a 45 watt solar system connected to two deep cycle batteries (in parallel). I am going to add a second 45 watt system (12v). Both have charge controllers. My question is. . .

    Can I just connect both solar systems to the post of one battery? Parallel circuit right?

    I just feel like I am missing something.

    In addition, if I get a 12 V wind turbine, then can I also connect that to the bank? (With a charge controller).

    What about both systems charging and adding a 12 V battery charger to boost the charge on the batteries.

    Thanks for your help.
  2. roddefig

    Active Member

    Apr 29, 2008
    Well, I'm not sure what effect the charge controller will have, but in theory you should be able to connect all of your voltage sources in parallel and not have any problems. Your batteries will charge faster thanks to the extra current. But, three charge controllers in parallel, that might not be so good.
  3. bertus


    Apr 5, 2008

    You can place the chargers parallel when you put a diode in series with each charger towards the accus.
    This is to prevent discharge when one (or more) of the chargers stops delivering.

  4. Wendy


    Mar 24, 2008
    Another way to do it (and not necessarily the best way). Switching regulators are extremely efficient, so if you were to put them in parallel you might get some interesting results. The killer is the passive resistance of the various components.

    The other thing might be to put them in parallel as suggested, but regulate them or convert them to a standard voltage, so they can all contribute equally if their working. By convert I'm talking boosting the voltage if that's what it takes.

    This is an opinion, I claim no expertise here.
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    Do not put the wind turbine in parallel with the solar panels unless diodes are used. The o/p of the wind turbine will vary as the wind varies. The o/p of the photovoltaics will vary as the light varies.

    A charge controller will protect your batteries.
  6. pathfind2003

    Thread Starter New Member

    Jun 22, 2008
    Makes sense with the diodes. Thank you - very much - for your replies. This is probably one of the best forums I have been on.:)
  7. SgtWookie


    Jul 17, 2007
    As far as diodes - I suggest that you use Schottky diodes. They have a much lower Vf (forward voltage) than standard rectifier diodes. This means that you will lose less power in them.

    International Rectifier's website has a great deal of information on selecting the best rectifiers for your application. It will be a very helpful resource for you.
  8. Cornelius


    Mar 17, 2008
    How much amps. can the controller for the existing panel handle? The best thing to do would be to connect the new panel Without controller in parallell to the other one BEFORE the existing controller; that way, you'll only have one controller for both panels.
  9. pathfind2003

    Thread Starter New Member

    Jun 22, 2008
    The present controller can only handle 4 amps (came with the kit)- the panels originally had an output of 45w - 12v DC but over time the Amorphous Silicon panels have lessened their output. It seems they lose about 8% of their efficiency over time then stop losing it. However, they seem to have higher output in low light than the more modern types. I plan someday to get a 30-50 amp controller, so I can continue to expand the system without new controllers, but the current system is on sale for $160 (controller, wiring, 2 5w DC CFLs, 3 panels at 15W each) - which seems to be a pretty good deal, so at least I have longlasting panels and adding a new controller will be cheap and a step that didn't cost extra $$$.

    My budget is requires me to find very cheap steps - even though it may cost a little more in the long run. It is kind of a learning experiment. Good suggestion though.