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My DIY Solar Ideas - Advice

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  • My DIY Solar Ideas - Advice

    Hi all

    I have a house with south facing rear garden in Warwickshire over looking fields with no trees.
    I have access to 12V AGM 110ah batteries, cable for free all year round.

    I plan to run a few panels on my roof (its about 30o) pitch and perfectly south facing, running cable into my garage with the batteries stored to charge up during the day, then in evening flick a switch to go over to running a few sockets in house off the batteries through an inverter of course.

    I have also been given a 150W and an unknown panel (Chinese crap I presume) and 2 20A charge controllers, so I can start this with £0 cost so far..... bar Im going to have to buy an inverter.

    Advice -

    How should I connect my batteries? 48V, 24V or just singles at 12V? (I can only charge at 12V at min as have 12V charge controller, but should I go 48V inverter?)
    Shall I connect them in HUGE bank? or only use as many as I think I need (Im thinking internal resistance etc...)
    Where are the critical cable length issues? Is it panel to charge controller, charge controller to batteries, batteries to inverter or inverter onto ring?
    Should I just change all my lights in my home to 12V and that be better then trying to use any 230V socket power for an hour or 2 each evening.
    What inverter should I buy?

    Anything else you can say? I know this is madness for most, but seeing as I have all this stuff for free so far and only ongoing costs would be more panels I think its of good financial sense and fun, correct?

    Cheers

    (Just realised this is a USA forum really. Im a UK guy)
    Last edited by Bikerz; 05-24-2016, 05:24 AM.

  • #2
    Hello Bikerz and welcome to Solar Panel Talk

    Anytime you wire batteries in parallel you run the risk of not charging or discharging them evenly which will end up killing one or more early on with the rest soon to follow. So while you may not currently have the correct charger it would be better to build a 48volt battery system. A higher battery voltage will also help with being able to use smaller wires over longer distances to meet the minimum voltage drop requirements.

    Next while I am more familiar with the US electrical codes I would imagine that using the power from your solar / battery system to energize any of your house outlets if you are still tied to the grid is dangerous unless you have the knowledge and experience to isolate both wiring systems.

    Also changing your lights to 12volts will cost you a lot of money and require very big wires between your battery system and your loads. It is best to use a DC to AC inverter to power specific loads individually from the inverter.

    And finally even with your free batteries and cable you might end up needing to purchase other equipment (solar panels, battery charger, inverter, over current protection, etc.) that would end up costing more to generate your power then to just purchase it from the grid.

    Now if you want to install a grid tie solar pv system then you have a chance to save money and get back what you invest over a period of time. More than likely free batteries will end up costing you something just to dispose of them when they die. Especially since from what you have stated I will presume ( i actually hate that word) that the batteries are not new and therefore have a very short lifespan.

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    • #3
      Thanks.

      Batteries are new (They have done an hour test above 80% SOC) so are better then any new ones you will get from a store. I also can get rid of free (In fact I get £10 for a used battery).
      Thanks for advice, maybe I should rethink my ideas then.

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      • #4
        Originally posted by Bikerz View Post
        Thanks.

        Batteries are new (They have done an hour test above 80% SOC) so are better then any new ones you will get from a store. I also can get rid of free (In fact I get £10 for a used battery).
        Thanks for advice, maybe I should rethink my ideas then.
        You are welcome. While using batteries to generate electricity may be expensive and never really pay themselves at least building a system correctly is worth trying as long as you do not invest a lot of money only to find out you do not get what you expect in power generation.

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