Help - 24V, 12V, Solar




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  1. #1
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    Default Help - 24V, 12V, Solar

    OK, some background, we have a Truck to transport the horses to Shows, etc. It Runs off Pure 24V, but we have a "Cabin" in the front, for lack of a better term, that we would like to power independently off 12V
    so, I am looking for something like the following:
    When Truck Runs, the 12V battery pack should charge from the 24V off the Truck - what do I need to get this sorted?
    Secondly, I would like to add a solar panel, to charge the 12V battery pack while standing for a couple of days, i.e. lights, fridge, etc can still be sued and battery pack can charge during the day

    Any elegant solutions to this? Or would it be better to go everything pure 24V? The thinking behind 12V is there are so many accessories., and is my mind it should be simple enough. I do not want to drain the Truck's 24V starting batteries, prefer to have the 12V system completely independent, just charging from Truck's alternator when the truck is running...
    Christo Davids
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  2. #2
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    Default Re: Help - 24V, 12V, Solar

    Christo in my personal opinion I would stick with the 24V. You already have 24V so simply buy a 24v inverter, 24 controller and two smallish panels (around 100W or one larger 24v panel) Add two batteries and have a solenoid between the two battery banks to cut off when the truck is standing still. The batteries charge whiled the truck is running and from the panels when standing.
    My way .... any other ideas ?

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  3. #3
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    Default Re: Help - 24V, 12V, Solar

    You can always step the supply voltage down to 12v for your gadgets.

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    Default Re: Help - 24V, 12V, Solar

    Christo, you will need some sort of a step down inverter.

    Hoe readily available those are from 24 - 12 I don't know.

    But this is what you'll need. Google those first.

    Once you have located such an inverter, the rest is easy. You just add whatever 12V accessory you need starting with a DC to DC charger for the extra battery you're going to ad.
    Last edited by Die SwartKat; 2018/06/18 at 02:31 PM.
    Nico Swart

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    Default Re: Help - 24V, 12V, Solar


  6. #6
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    Default Re: Help - 24V, 12V, Solar

    Quote Originally Posted by Karoo Klong View Post
    Yes there you go.
    Nico Swart

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  7. #7
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    Default Re: Help - 24V, 12V, Solar

    Thanks Guys
    say we add 2 additional batteries and stick to 24V, how do I charge the additional batteries, without draining the main batteries? Is there a Cole Heresee equivalent for 24V, to basically isolate the 2 batteries from the Crank batteries?
    Christo Davids
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  8. #8
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    Default Re: Help - 24V, 12V, Solar

    Quote Originally Posted by Christo Davids View Post
    Thanks Guys
    say we add 2 additional batteries and stick to 24V, how do I charge the additional batteries, without draining the main batteries? Is there a Cole Heresee equivalent for 24V, to basically isolate the 2 batteries from the Crank batteries?
    The Cole Herschee solenoid is merely an automatic switch that completes a circuit when it receives power. 12V power as we know it.

    If they are available in 24V I have no idea.

    If not, or unreasonably priced, go the manual way with a battery kill/isolation switch?

    But then again you will be stuck with a 24V system for which you say there are very little accessories.

    I'd stick to 12V and couple the CH inline after the inverter.
    Last edited by Die SwartKat; 2018/06/20 at 08:01 AM.
    Nico Swart

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  9. #9
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    Default Re: Help - 24V, 12V, Solar

    OK, so if I am getting this correct:
    24V Main batteries
    Connect one of these:
    https://www.wantitall.co.za/electron...of__b00bwkxtuu
    i.e. output now 12V, and connect the 12V aux batteries to that? Maybe with a Manual Switch to Swith on to charge, or is there a way to automatically only draw power from the 24V batteries while the truck engine is running? Should I asdd something like tht NL solenoid between the 24V to 12V Step-Down and the battery?
    Christo Davids
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    Default Re: Help - 24V, 12V, Solar

    On Second thought, will this work:
    Connect Main battery to This https://www.wantitall.co.za/electronics/dc-24v-to-dc-12v-step-down-30a-360w-heavy-duty-truck-car-power-supply-adapter-converter-reducer-regu__b01jaic7oo
    Connect 12V end of Step Down converter to this charger:
    http://www.4x4direct.co.za/dc-to-dc-...olar-mppt.html
    Connect Solar Panel to the WRND Charger as well...
    Connect that to Aux 12V battery?
    All should be OK, or will the Step-Down transformer from 24V to 12V not supply sufficient voltage to activate the Charger?
    Last edited by Christo Davids; 2018/06/20 at 09:33 AM.
    Christo Davids
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  11. #11
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    Default Re: Help - 24V, 12V, Solar

    Quote Originally Posted by Christo Davids View Post
    On Second thought, will this work:
    Connect Main battery to This https://www.wantitall.co.za/electronics/dc-24v-to-dc-12v-step-down-30a-360w-heavy-duty-truck-car-power-supply-adapter-converter-reducer-regu__b01jaic7oo
    Connect 12V end of Step Down converter to this charger:
    http://www.4x4direct.co.za/dc-to-dc-...olar-mppt.html
    Connect Solar Panel to the WRND Charger as well...
    Connect that to Aux 12V battery?
    All should be OK, or will the Step-Down transformer from 24V to 12V not supply sufficient voltage to activate the Charger?
    The first unit should provide you with a clean 12V only, and I suspect will not charge the battery sufficiently, as you need something closer to 13-14V. Using a MPPT solar controller, you can connect it directly to the 24V and it will happily charge your 12V batteries. As you still have the issue of charging when stationary for days, add a solar panel or two on the input of the MPPT controller, BUT:
    1) you'll need a three way switch to toggle between off, and either solar or 24V battery as your input supply
    2) that switch must be able to switch 30Amps (and fuse both inputs!)

    This should be the easiest and fewest components/connections in my opinion. Also phone a few 4x4 shops for their advice and speak to their experts...

    Victron MPPT spec sheet - https://www.victronenergy.com/upload...-100-15-EN.pdf
    Last edited by larry007; 2018/06/21 at 02:03 PM.

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  12. #12
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    Default Re: Help - 24V, 12V, Solar

    A client of ours has just bought a horsebox.
    It has a 105 ah deep cycle battery charging off one of the main batteries, through a T Max dual battery charger with a solenoid.
    One of these https://www.jgs4x4.co.uk/t-max-12v-s...tatus-monitor/
    All the battery is running at the moment is the cabin lights, but were going to put a fridge etc in there soon.

    If you need to see how its wired give me a shout and we can probably meet up at a show one day.


    My worry is that the charging voltage is not high enough to properly charge the deep cycle - the truck batteries are only at about 12.4V, and the deep cycle is sitting at about 12.3v I need to check what the voltage is when the truck is running.

    Another issue with these horseboxes is they generally do very short trips - average about 45 minutes to a show every 2nd weekend. Surely this isn't enough to properly charge the batteries?

    I think putting a panel on the roof to keep the main batteries charged would be a good idea. At least it will keep the batteries topped up, and will help to keep the deep cycle charged too.
    we have a spare 140 ah truck battery lying around - Id like to connect this to the deep cycle to run the fridge etc As far as I understand we will be limted to the power of the smaller battery, but will this still give us 200 amp hours, and will the T max controlled be able to handle it?
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  13. #13
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    Default Re: Help - 24V, 12V, Solar

    You can use an equalizer as well.
    It is a gadget which allows the near equal discharge and charge of 2 x 12 V batteries in a 24V setup.

    Locally HCdP Electronics in Pretoria manufactures it yet there are other options from overseas available as well.

    Personally using such system in Abba Camper to power 12V lights & water pump and 24V inverter.
    Last edited by Matsipane; 2018/07/15 at 08:13 AM.

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