Low draw 12 volt power supply

Bigwooo
Bigwooo Solar Expert Posts: 62 ✭✭
in Off Grid Solar & Battery Systems #1
I'm looking for a 12 volt power supply that has a low amp draw. I'm currently constructing my off grid home and would like to have 12 volt garden lights and a few 12 volt interior lights as well as a couple of 12 volt accessories inside the house.

My system is 12 volts, but I'd like to avoid running 60 feet of 2/0 cable from the utility room to a 12 volt sub panel in the house if I don't have to. It would be easier to convert 120 to 12 volts from a 12v charger.

What I would like to do is find a good battery charger/12 volt power supply (20 - 30 amp would be more than enough) that doesn't have a huge draw when in use, or in idle, to provide the DC power

Most chargers/power supplies I've read up on don't provide much info on current draw in their documentation. I'm looking for something that can go into an idle mode, and doesn't draw current 24/7 when not in use....if that exists.

I don't want to have to turn it on/off when I want to use something that runs off 12v. I would like to hardwire it in and leave it on 24/7 if I can find something with a low draw.

Anyone have any suggestions on a low draw/good quality charger/power supply that would fit this criteria?
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: Low draw 12 volt power supply

    Are you looking for DC or AC power (LED's, other filament bulbs).

    Also, a battery charger is typically not a good solution... Unless you are charging battery; some chargers will not turn on without a battery connected, and other chargers are simply DC rectifiers with no output filtering plus peak/ripple voltages well above "12 volts".

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
    Re: Low draw 12 volt power supply
    Bigwooo wrote: »
    What I would like to do is find a good battery charger/12 volt power supply (20 - 30 amp would be more than enough) that doesn't have a huge draw when in use, or in idle, to provide the DC power

    Check the Iota chargers, I think they were designed as Power Supplies, and when you don't pull much from the output, the input folds back
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • Bigwooo
    Bigwooo Solar Expert Posts: 62 ✭✭
    #4
    Re: Low draw 12 volt power supply

    B.B.: I'm looking to provide 12 volt DC from a 120 volt AC supply.

    Mike, thanks, I'm looking into the Iota's right now.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #5
    Re: Low draw 12 volt power supply
    Bigwooo wrote: »
    I'm looking for a 12 volt power supply that has a low amp draw. I'm currently constructing my off grid home and would like to have 12 volt garden lights and a few 12 volt interior lights as well as a couple of 12 volt accessories inside the house.

    My system is 12 volts, but I'd like to avoid running 60 feet of 2/0 cable from the utility room to a 12 volt sub panel in the house if I don't have to. It would be easier to convert 120 to 12 volts from a 12v charger.

    What I would like to do is find a good battery charger/12 volt power supply (20 - 30 amp would be more than enough) that doesn't have a huge draw when in use, or in idle, to provide the DC power

    Most chargers/power supplies I've read up on don't provide much info on current draw in their documentation. I'm looking for something that can go into an idle mode, and doesn't draw current 24/7 when not in use....if that exists.

    I don't want to have to turn it on/off when I want to use something that runs off 12v. I would like to hardwire it in and leave it on 24/7 if I can find something with a low draw.

    Anyone have any suggestions on a low draw/good quality charger/power supply that would fit this criteria?

    What is the expected current draw on the dc side of the these few lights and other things.Using LED lamps will keep it very low.Do the appliances need a good quality dc source.I would still be tempted to use the 12 volts you have and check the voltage drop you will have with the expected amps.Converting dc to ac then back to dc will add loses and more complication.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #6
    Re: Low draw 12 volt power supply

    Going from 12 volt to 120 volt then back to 12 volt if I am reading this correctly.

    Losses,
    12 to 120 about 20%
    120 to 12 about 30%

    so total losses are about 50%

    Wire maybe a better way to go.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: Low draw 12 volt power supply

    i think i agree with ken and run the wire. you may not need 2/0 and you can use the voltage drop calculator to determine where you stand on losses. besides the conversion losses you will have losses on the supply itself to run with or without loads and how many times will you be using small loads that may draw as much as the supply to idle does thereby doubling the power consumed? or maybe forget to shut the supply off all together?
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  • Bigwooo
    Bigwooo Solar Expert Posts: 62 ✭✭
    #8
    Re: Low draw 12 volt power supply

    As an update, I wound up installing this transformer http://www.landscapelightingworld.com/Low-Voltage-Landscape-Transformers-s/31.htm to power all my low voltage exterior lighting. It has zero power draw other than what the lights actually use. It's been up and running for about 8 months now an I'm very happy with it. I decided to use low voltage garden lighting because there is a greater variety of lighting available.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: Low draw 12 volt power supply

    whatever works for you. ftr there's no transformers that are 100% efficient, therefore you have losses no matter how large or small these losses may be. i saw the prices on those transformers and my jaw dropped.:cry:
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