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Charging 2*SLA battery from Solar

Discussion in 'Electronic Basics' started by Pete D, Apr 2, 2007.

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  1. Pete D

    Pete D Guest

    I have an application that requires 2 12V 7.5 AHr lead acid batteries to
    be charged from 2 nominally 12V but actually nearer 18V with no load
    1.5A solar panels, in the end i hope to get away with 1A solar panels
    but first I need to accomodate 1.5A panels.
    I don't just want to put a diode in series for risk of overcharging the
    batteries.

    If I could find a suitable charge controller at a reasonable price I
    could buy them in, but I cannot find one.

    so looking at building something, I have PIC in circuit anyway for other
    reasons, I am considering PWM'ing the solar output to keep it at 27.6V
    but this area is new to me, indeed I am not sure this is the best
    approach, any ideas on whether this is a suitable approach or if not
    what is?

    Pete D
     
  2. Ross Herbert

    Ross Herbert Guest


    What do you consider "a reasonable price"?

    Also, the price depends on where you are located or trying to buy
    from. You didn't say you were in the UK....

    You don't need a 'big' controller, something like the SG4 would be
    suitable
    http://www.midsummerenergy.co.uk/buy_solar_panels/morningstar_controllers_solar_regulators.html

    or this
    http://www.sunshinesolar.co.uk/item--Charge-Controller-SolarPRO-<BR>7-AMP-105W--regulator7amp

    If UKP26 is too much then maybe you could consider buying it in from
    thr US http://store.solar-electric.com/sg-4.html where they have it on
    special for USD28.50. Surely this isn't too expensive - after all
    building one yourself will probably cost twice as much after buying in
    all the bits.
     
  3. Pete D

    Pete D Guest

    Yes I am in the UK, I was only just yesterday reminding an American
    cousin not to assume all posters were American, Oh my mind it goes a
    little every day;-)

    thanks for the links, they look fine except being 12V not 24V, I guess I
    could use 2, but not sure thet'd work and indeed it doubles the cost and
    space which is in short supply in the box it's got to go in.

    At least those links suggest my idea of PWMing the supply from the solar
    panels as auitable means of charge control.

    Again many thanks

    pete d
     
  4. Ross Herbert

    Ross Herbert Guest


    Sorry, I made the assumption that you were running the batteries in
    par'l. Bad me...

    A 24V controller will cost a bit more.
    http://www.midsummerenergy.co.uk/buy_solar_panels/morningstar_controllers_solar_regulators.html
    Morningstar SS6 at UKP40 would do fine.
     
  5. Pete D

    Pete D Guest

    Not sure about bad you, I didn't specify I wanted to do them in series,
    6A with 25% overload for 5 mins, would do very nicely at that price, I
    think they only seem to do the 10A in 24V, but that is now really a
    problem, i'd like to allow for 7.5 - 8vA at overload though we only need
    it to work for a minute or so several times a day.

    I am getting slow in my old age, you sent me to a page with the info on,
    I just didn't raed it all well enough.

    thanks again for the help.

    regards pete d
     
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