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Thread: 24v to 12v conversion

  1. #1
    Join Date
    Jan 2010
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    Default 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? 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

  2. #2
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    Default 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.
    NIEL

  3. #3
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    Default 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!
    http://members.sti.net/offgridsolar/
    "we go where the power lines don't"

  4. #4
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    Default Re: 24v to 12v conversion

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

    Eric
    100% Off Grid @ 51* 46' N lat 124* 44' W long

    New House system: coming - 2 arrays @ 2240W
    CL150&Epanel 2 @140 W 12v PVs , 24V C&D AT-15P AGM @ 950Ah
    + CL150 2@120W 12 V panels, 24V C&D AT-15P AGM @ 950Ah
    Cotek ST1500W inverter, TBS 30a-24v Omni-charger, Honda Eu3000is,

    Guest cabin system: 3 - 70W panels to SB 2000e CC, with 2 - 100 ah 12v SAFT wet NiCd's , 600W TSW Inverter

  5. #5

    Default 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.
    1220 Watts of PV, OB MX60, 232 Amp hrs, OB 3524, Honda eu2000.

    Ohm's Law: Amps = Volts / Ohms
    Power Formula: Watts = Volts * Amps

  6. #6
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    Default Re: 24v to 12v conversion

    You can use one of these if power requirement below 25 watts
    http://www.dimensionengineering.com/DE-SWADJ3.htm
    15 assorted solar panels 1800 watts
    MX 60 charge controller
    940 amp hour 2 X 6-100-13 DEKA batterys
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    SW4024 inverter
    Basic Stamp computer to control SW4024 from MX60

    MikeO

  7. #7

    Default 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.
    1410w PV in two 48v arrays, MX-60 (710W) and Tristrat MPPT-60 (700W), 3 1104AH Rolls 4V batteries in series for 12v battery bank, powering various household LED lights, washing machine, laptop and gadget charging and a super low power server. AC and entire home office (switchable) on sunny days when power available comes from 1500w heavy duty "industrial" samlex sine wave inverter with high surge. Also, 1.9kw(DC) gridtie system (Sanyo HIT's).

  8. #8
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    Default Re: 24v to 12v conversion

    Quote Originally Posted by westbranch View Post
    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

  9. #9
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    Default Re: 24v to 12v conversion

    Quote Originally Posted by Cariboocoot View Post
    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

  10. #10
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    Default Re: 24v to 12v conversion

    Quote Originally Posted by Dave Sparks View Post
    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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