24v to 12v conversion

RoySalisbury
RoySalisbury Solar Expert Posts: 84 ✭✭✭
in Off Grid Solar & Battery Systems #1
I have a 24v battery bank. I also have some devices that would operate at 12v directly, or via an AC adapter (120v to 12v converter). What I would like to know is what would be the best way to use my 12v devices? Do I run them through the inverter in the AC current (that then switches back to 12v for the device), or get a 24v to 12v converter and install a few "12v plugs" where needed?

If the 24v to 12v conversion is best, can anyone recommend a low loss device that I can get to hook up to my battery bank. There will not be a long distance of wire length (15-20 ft) so wire size may/may not be an issue.

Thanks!

Roy
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Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
    Re: 24v to 12v conversion

    that's a tough call for us to make and i think it is more of what is cheaper for you to do. the 24 to 12v converter may be slightly more efficient, but the 120vac inverter may add more versatility with variable or changing needs. make no mistake about it here as both actually invert the dc to a higher voltage and back down with the inverter needing the wall adapters or power supplies to go back down with. higher dc current loads may require a power supply to be connected to the inverter output and some power supplies may be costly so do some research and some math to know which is better for you.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #3
    Re: 24v to 12v conversion

    How long do you want to do this for? For a short time, you can fuse the 12 volt load, 6" from the 24 volt bank. You will be braking a basic rule and this is a poor practice. However, I have done this or "ok'd" it for someone who is building a house or busy with other things for a short time. There are plenty of 24V appliances, CFL's, pumps, chargers, fans, electronic components, ect. You should not wait long to make the switch if your battery bank is worth it long term!
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #4
    Re: 24v to 12v conversion

    Roy, what are the devices? That may help determine a viable course of action.

    Eric
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: 24v to 12v conversion

    If you've already got the inverter, just go with AC runs. It'll be easier and allow flexibility in placing things, and it will be cheaper than buying a DC-to-DC converter.
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #6
    Re: 24v to 12v conversion

    You can use one of these if power requirement below 25 watts
    http://www.dimensionengineering.com/DE-SWADJ3.htm
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  • lamplight
    lamplight Solar Expert Posts: 368 ✭✭✭✭✭✭
    #7
    Re: 24v to 12v conversion

    theres some stuff here

    i run a few things directly off 12v for the efficiency factor, but then my bank is 12v for that reason and its small. converting 24 to 12v will really be more efficient and if they are low wattage loads you should be able to do your cable lengths no problem. with a converter rated for a larger draw you could runa bunch of stuff off the 12v directly as long as there isnt too much voltage drop. a few years ago i tried running my office pc off 12v directly and was getting way to much voltage drop, the pc would not power on due to startup draw. i run ac from an inverter now.


    now we charge cell phones, ebook reader, laptops , etc direct off of 12v. (each using its own 12 to whatever converter, 18v for laptop, 5v for cell, etc.. )


    id agree though, now that my system is a little larger , having a AC inverter and running everything off of that is not too inefficient as the thing is running all the time anyhow, so these small charging loads are nothing, and gives super flexibility in running long cable runs.
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  • RoySalisbury
    RoySalisbury Solar Expert Posts: 84 ✭✭✭
    #8
    Re: 24v to 12v conversion
    westbranch wrote: »
    Roy, what are the devices? That may help determine a viable course of action.

    Eric

    That is a good question. Some are things like fans and a small colman cooler and that might be easier to replace. But others are cameras and telescope equipment that can't be. For these its either 12v DC or 120v AC.

    I can do everything off the AC, but want to try to save every watt I can since it it all totally off grid and what the sun does not provide, I don't get to use.

    Roy
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  • RoySalisbury
    RoySalisbury Solar Expert Posts: 84 ✭✭✭
    #9
    Re: 24v to 12v conversion
    Cariboocoot wrote: »
    If you've already got the inverter, just go with AC runs. It'll be easier and allow flexibility in placing things, and it will be cheaper than buying a DC-to-DC converter.

    I'm beginning to think your right. But I want to make sure I have explored all the possibilities since I need to save every watt I can. I just figured it was wastful to go from 24v DC to 120v AC and then back to 12v DC.

    Roy
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  • RoySalisbury
    RoySalisbury Solar Expert Posts: 84 ✭✭✭
    #10
    Re: 24v to 12v conversion
    Dave Sparks wrote: »
    How long do you want to do this for? For a short time, you can fuse the 12 volt load, 6" from the 24 volt bank. You will be braking a basic rule and this is a poor practice. However, I have done this or "ok'd" it for someone who is building a house or busy with other things for a short time. There are plenty of 24V appliances, CFL's, pumps, chargers, fans, electronic components, ect. You should not wait long to make the switch if your battery bank is worth it long term!

    I'm going to try to avoid doing this. I knew it was possbile, but everyone says avoid it becuse it can make the charge in your batteries uneven hence they won't last as long.

    Roy
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  • RoySalisbury
    RoySalisbury Solar Expert Posts: 84 ✭✭✭
    #11
    Re: 24v to 12v conversion
    mikeo wrote: »
    You can use one of these if power requirement below 25 watts
    http://www.dimensionengineering.com/DE-SWADJ3.htm

    Thanks. I'll take a look at the device. under 25 watts is not a probelm for some of the devices. Just need to see what the effiency is.

    Roy
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  • mikeo
    mikeo Solar Expert Posts: 386 ✭✭✭
    #12
    Re: 24v to 12v conversion

    Hi Roy, do you know my astronomer friend Al Grauer at Mt Lemmon? He and I used to work together. If you know the DC loads, you could match multiple inexpensive converters for your 12 volt loads.
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  • Opti
    Opti Registered Users Posts: 10 ✭✭
    #13
    Re: 24v to 12v conversion

    I'm interested in the answer to this topic too but don't have a solution yet.

    What I can add is this:
    http://bus.getdave.com/Docs/12Von24V/

    The article mentions a Battery Equalizer like one of these:
    http://order.waytekwire.com/DATASHEET/80100.pdf
    Which are 91%-94% efficient at pulling 12v off a 24v battery system

    Of this one which is up to 97% efficient:
    http://www.merlinequipment.com/markets/group.asp?groupid=33

    SolarConverter makes this autotransformer 20A version which is common among solar shops and can also be connected as a battery equalizer:
    http://www.solarconverters.com/equal1.htm

    They aren't cheap but for a constant 12v supply off a 24v battery system they appear to be one of the better options.

    Articles mentioned that these type of devices are found on old buses so you maybe able to salvage one for much less than new.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #14
    Re: 24v to 12v conversion

    Interesting 24 to 12 volt converters/battery balancers.

    Looks like it should work well... I do wonder if there is any impact on long term battery life between the upper 12 and the lower 12 volt battery banks.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • sweetchuck
    sweetchuck Registered Users Posts: 13 ✭
    #15
    Re: 24v to 12v conversion
    I have a 24v battery bank. I also have some devices that would operate at 12v directly, or via an AC adapter (120v to 12v converter). What I would like to know is what would be the best way to use my 12v devices?


    I use a converter to run all the 12v DC in my RV from 8 golf cart batteries at 24v. It's rated for 30 continuous amps. Works like a charm.

    http://www.newmarpower.com/DC-DC_Converters_Standard_Isolated_Series/DC-DC_Converters_Standard_Isolated_Series.html

    You can find them on ebay for less than $200, sometimes.

    Good luck.
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