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12v car barrery to 6v to run led lighting and 6v radio incorperating a solar pannel

Discussion in 'LEDs and Optoelectronics' started by giffy121, Apr 8, 2012.

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  1. giffy121


    Apr 8, 2012
    ive got an alotment and have no elecricity, my idea is to use a car battery to run leds which run on 6v dc, and a radio which runs on 6v dc but in corparate a 12v solar pannel to trickle charge the battery its a maplin 12v 1.5w trickle charger i am new to elecronics so im a bit stuck. as im worried that when i connect solar pannel the voltage will increase the battery output:confused:
    any help would be gratefully recived :)
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    If you're using 12V batteries, you need a 12V charger designed to run from solar panels.

    You need equipment rated for 12V. For lighting, LED lights incorporating switchmode current regulation is your best bet.

    For your 6V radio (the current requirements are likely to be small) you should have a dedicated 6V regulator to power the radio connected to the 12V supply.

    Your 12V supply can vary from about 14.5V down to 10.5V, so it is important to have loads that are capable of operating efficiently from that range of voltages.
  3. giffy121


    Apr 8, 2012
    the solar pannel is a trickle charger designed for 12v car batteries and what 6v regulator would you reccomend as i want a reliable one thanks
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Oh, I didn't read that it was a trickle charger.

    Is that the entire source of your power? It's not going to provide much power.

    What is your lighting load? I would expect that if you're in the UK you'll get the equivalent of maybe 4 hours of sunlight per day in winter (maybe significant;y less)

    OK, the UK met office says 2 hours in January and December apparently.

    So a 1.5W panel can deliver 3Wh per day during winter (and that's only on days without cloud or fog). That 3Wh will run a 0.5W LED for about 6 hours. It's also the load that a small radio would generate. So you could have 3 hours of something like candlelight with radio per day.

    To allow for days that are cloudy/rainy/foggy, etc, you would halve that (or even cut it by 2/3).

    Is an hour of feeble light good enough for you? Is 2 hours OK if you don't use the radio?

    in contrast, a 40W panel would provide 80Wh/day in winter, which would allow you to run a load of just over 3W for 8 hours. A 3W LED light is actually pretty bright, and the system starts to look like it has some value.

    Note that the calculations above do not take into account several inefficiencies such as losses during charging and resistive losses in cables which will make the figures look even more depressing.

    Going up to a 150W, or 175W panel will give you the ability to run a sizeable load (like pretty good lighting) all night in winter. As you get to these size panels, a dedicated MPPT charger is essential and you're also going to have to size your batteries appropriately.
  5. giffy121


    Apr 8, 2012
    its not the power source, i was thinking of using the solar pannel to top up the charge on a 12v car battery and use the battery to run the leds and the radio
  6. cjdelphi


    Oct 26, 2011
    As long as the battery does not go over 15v (and even if you tried it would not do much as the electrolyte would just boil away very slowly)

    You will have more wind than solar, a 12v wind generator?
  7. Audioguru


    Sep 24, 2016
    You di not understand that the trickle charger supplies only a small amount of power. It is designed to supply only the small loss of charge an unused battery loses each day.
    If you use only a trickle amount of light and only a trickle amount of radio each day then you can use the trickle charger.
    Or you can use most of the power from the battery in one day and let it charge for a month when you have no light and no radio.
  8. Gryd3


    Jun 25, 2014
    Your battery is simply a reservoir for storing energy from the solar panel.
    You need to budget around the *panel* and not the battery.
    As stated earlier, you can expect to get no more than 3Wh of energy per day. Sure, you can use more than that to begin with, but you will soon find your battery flat. Having a large battery would only be a benefit if you very infrequently used it.
    The questions that need to be answered now are:
    - Are you willing to buy a new/additional solar panel?
    - Is music necessary?
    - What is your minimum required amount of light?

    From here, we can begin to assist and suggest which lighting you should/can use and how long it may last. We can also advise you that running audio will cut your daily allotment by a considerable amount, but we do not yet have the details to say by how much.

    You really are working with a very small amount of power. To put this into perspective, current cell phone chargers run at 5V and may supply 1000mA or 2000mA which is 5W - 10W. Plug in a new iPhone to your system and you would use your daily allotment in 30-minutes. The little Li-Ion battery in the Samsung S4 is 9.88Wh which would take approximately 8 hours of sunlight to charge.

    Depending on your answers and how frequently you want to use your system, you may be better off buying a set of AA batteries or larger and simply taking them with you to-from a site with power to charge/top-up.
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