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Electrical gurus!!! Need 24 volt power. More questions!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by grumpy, Oct 30, 2002.

  1. grumpy

    grumpy 1/2 ton status

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    I have a power inverter that runs on 24 volts. I have 2 12 volt batteries. How can I wire this thing up so the inverter gets 24 volts and the rest of the Blazer gets 12? I need to isolate the 2 systems but do not know how. I know the Hummer has this setup but not how it's done.
    The deal is that the inverter I have was free and it is 5000 watts so I really want to use it. Is there a way to run both 12 volt and 24 volt circuits from the same 2 batteries? Like some kind of one way in-line electrical valve?
    Thanks,
    David
     
  2. u2slow

    u2slow 1/2 ton status

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    Re: Electrical gurus!!! Need 24 volt power

    I assume the Hummer uses a setup very similar to the CUCV's. Here's an overview on how to convert from mixed 12/24V to 12V:
    24V article

    Look like they use a separate 24V alternator /forums/images/graemlins/eek.gif

    Probably the easiest way is to run the batteries in series for the 24V inverter, but then run the truck off just one of these two. Dunno how you make sure both get charged though /forums/images/graemlins/confused.gif
     
  3. BARRAZA

    BARRAZA 1/2 ton status

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    Re: Electrical gurus!!! Need 24 volt power

    The CUCV's have a 24 volt starter and special floating ground alternators. Both alternators are 12v but one of them uses 12v on what would normally be the ground side and thus produces 24v output. Two huge resistors drop the voltage for everything except the starter. You dont want to convert to the CUCV type system because the special alternators and starter are expensive, probably much more expensive than selling the inverter you now have and getting one that runs off of 12v
     
  4. jjlaughner

    jjlaughner 3/4 ton status

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    Re: Electrical gurus!!! Need 24 volt power

    I dont know if it would help, but can you run a dual post battery on one of the batteries and use the second set of terminals?
    I run all my truck stuff off the side post as many 87 trucks use. But I use the top posts for my amp and lights. I usually trade batteries every two or three years but thats not bad. Use the side posts for you 12v and use the top posts to run series for your 24v? Good luck, J
     
  5. u2slow

    u2slow 1/2 ton status

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    Re: Electrical gurus!!! Need 24 volt power

    Maybe pop open that inverter and see it has a 12V hookup. Most inverters on the market will accept a few different input voltages - maybe the one you have has been "dumbed down" with a specific application in mind. (i.e. military spec?)
     
  6. Overkill

    Overkill 1/2 ton status

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    Re: Electrical gurus!!! Need 24 volt power

    In order to piggyback your two batteries, one would have to be ungrounded from the chassis. IF you can spare one of your batteries for just the inverter, it would be simple. But Im sure you don't want to limit one whole battery for just an inverter. You could invert 12v and step it up with a xformer and then re-rectify it to 24v. But if you're dong that, why not just use the 12v inverter... /forums/images/graemlins/blush.gif. Get a 12 and be done with it, /forums/images/graemlins/laugh.gif. Or you could use battery isolators on one battery and when you need the inverter, you can flick a switch that would unground one battery and series your inverter connection to the other....?? Should be a simple circuit, but then it would also have to disconnect anything else hooked to that battery (Second one). It would probably be cheaper to get a 12v interter..
     
  7. grumpy

    grumpy 1/2 ton status

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  8. imiceman44

    imiceman44 1 ton status

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    You can wire the batteries in series and use 12v for everything else, but your problem would be charging.
    If you run 2 alternators and they both are isolated then you can do it, you can use both batteries for anything you want and you would be able to use the 24v inverter.
    If you don't and you try using a 24 volt to charge them both and use 12 volts on one of them, the charging will not be balanced and one of the batteries will dies fast, I know because I tried that for years on my inverter for the computer.
    Your only way to be able to use it and still have everything available and usefull, is to locate the military CUCV alternators and as someone said here, they are expensive.
    I am not going to say buy another because I know how much a 5000 would cost /forums/images/graemlins/frown.gif
     
  9. Pookster

    Pookster 1/2 ton status

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    Its pretty straight forward, but you have to keep in mind to use two identical batteries of the same age. (meaning go gets two new batteries). This is important, cause if one is more worn out than the other, or of a bigger rating, one will try to drain the other.

    Basically you will run the following parallel/serial combination:

    Lets assume the following: You have:
    Your truck running at 12V
    Two batteries at 12V 80AMhr
    24V inverter

    You would have to wire up the batteries as such:

    For inverter, you need both batteries hooked into serial. this will give you 24V @ 160Ahr. It is recommended by all the sources I have read that you connect one post on battery A and the other post on battery B (negative and positive respectively).and use a 0/1 gauge cable between the negative of battery A to the positive of Battery B.

    You would do this configuration, with or without Your truck involved.

    Now, to make sure all this stuff is being charged, you would simply hook up your your car to only one battery. In theory, it should drain from both batteries equally. In practice, the one closest gets a little bit more of a workout, but not significantly.


    There's a company that makes specialty posts for this kinda stuff. But also remember, your inverters, I dunno what make and model you have, but they have specific requirements. Most don't like to work below 10V, 24v units are somewhat more inefficient it seems than 12v systems, and they require a minimum of 2 batteries, and recommend at least 4. Also remember your power delivery needs. You'll wear out car batteries fast using an inverter. Go with marines if you can fit them. (Two marine batteries in parallel has like 1000 Cold cranking power and like 230ahr of reserve). Plus, they tolerate deep draining too.

    Your supposed to calculate your needs as follows:

    10% loss of efficiency in power transfer
    10% loss due to conversion

    If this is a 5000 watt continuous unit, good luck. THose things chew through batteries like a pitt bull on LSD. /forums/images/graemlins/1zhelp.gif

    If you need more help, send me a PM. I have a bunch of websites you can look at for diagrams and such.

    /forums/images/graemlins/thumb.gif
     
  10. imiceman44

    imiceman44 1 ton status

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    Sorry to tell you that, but NO, if you charge one battery in a series setup, the other will get nothing, only if they are in parallel. I know because it is my business and has been for the last 18 years. If you want to use batteries in series, you are right they must be of equal age and size.
    I deal with inverters, chargers, and batteries, and I know first hand from experience with the subject.
     
  11. Blue85

    Blue85 Troll Premium Member

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    It can be done. I see three possible solutions:

    1) Run 2 batteries and two alternators.
    The second battery and alternator have to be seperated from the chassis. They will both be grounded to your current +12V.

    2) Live with the idea of being able to only charge or only discharge at any given time. You still need two batteries, but only one alternator. Use a switch to change the batteries from being in series to being in parallel. This is no simple switch. It has to be DPDT and rated for hundreds of Amps. I don't know where you would get one, maybe a marine shop? Then the batteries are in parallel for charging and in series for running the inverter. You would basically have to have the engine off for this since you don't want to charge just the lower battery.

    3) Buy two more batteries (or 1 24V battery) and a second alternator.
    Use the existing battery just like it is now and put the two new ones in series as a 24V bank just for the inverter. The second alternator can either be a 24V one or a 12V one that is isolated.

    Whatever you do, it is a good idea to use deep cycle batteries. It would also be nice to have a reserve battery just for starting.
     
  12. imiceman44

    imiceman44 1 ton status

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    I agree with blue on the one alternator, and a combination of switches to switch from parallel to series, but it would be a lot of work for you but the cheapest.
    I personally would rig a dual setup and make it work permanently, but then again I like chalenges and have the background to do it /forums/images/graemlins/smile.gif
     
  13. grumpy

    grumpy 1/2 ton status

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    Iceman,
    Is the such a thing as the one way electric valve I described?
    David
     
  14. imiceman44

    imiceman44 1 ton status

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    The only one way electrical that I know of is the diode.
    It will let the curent pass only in one direction.
    That is what they use in the isolators, but with a few other components to make pulsating charging for the secondary battery, and a cuttoff when there is no current from the Alternator.
    I don't have the time to figure out a system for now but I will soon have to since I have a diesel Van that I am converting to 4wd and camper and I want to have all these alternatives. So when I do, I will probably post an article with all the details.
    I also heard about some mosfet swithces that are used with high amp amplifiers so I need to check these out and see what they can be used for.
     

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