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Thread: Emergency Charging of Aux Battery

  1. #1
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    Emergency Charging of Aux Battery

    My 101 is 24v in in the past my aux 12v battery was charged via a second 60amp 12v alternator. The aux battery is a deep cycle and powers typical aux items such as fridge, camp lighting etc but also the ignition system and 12 accessories in the cab.

    I am replacing the 12v alternator with a 24v - 12v 60 amp 3 stage Dc - Dc charger. I did have the 12v alternator fail a couple of times and given the amount of dust that gets into the cab of a 101, I am sure the dust will get into the charger with possible failure at some stage (I will be putting filtration on the cooling fan). I would like to include a backup system that will as a minimum provide 12v power to those things that need power when the engine is running.

    I just bought a neat little waterproof 24v to 12v 10 amp converter to run my fuel pump and they also sell 40 and 50 amp versions.

    So my simple question is would a 24v -12v 40 amp converter (not a charger) be able to charge a deep cycle battery in an emergency?

    Thanks

    Garry
    Last edited by p38arover; 5th July 2018 at 07:35 PM. Reason: Sadly, no electric thongs
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    Stab in the dark here. I think it would charge but limited. I think the reducer voltage will be regulated below 14.3 volts .I think. Just thinking out loud.

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    Have you considered using solar panels for the aux?
    I have had a 150w panel fitted to my 79 series roof that charges 2x 120ah batteries and it can run a 120l twin zone fridge the we are using as a freezer at -15C and it does this effortlessly.
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    Emergency 12v

    If its purely an "in an emergency" 12v power that you need to power the ignition, just take 12v from the link between the two batteries that make up the 24v system. It wont do the batteries any favors long term, but if its just to get you home in case the DC-DC fails it will be fine.

    You can do it more properly by using a charge equalizer, but again, if its just an emergency backup, keep it simple .

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    Quote Originally Posted by trout1105 View Post
    Have you considered using solar panels for the aux?
    I have had a 150w panel fitted to my 79 series roof that charges 2x 120ah batteries and it can run a 120l twin zone fridge the we are using as a freezer at -15C and it does this effortlessly.
    Without elaborate framing it is a bit hard to put panels on the canvas roof plus a bit hard to generate power when driving at night.

    Quote Originally Posted by RedBear View Post
    If its purely an "in an emergency" 12v power that you need to power the ignition, just take 12v from the link between the two batteries that make up the 24v system. It wont do the batteries any favors long term, but if its just to get you home in case the DC-DC fails it will be fine.

    You can do it more properly by using a charge equalizer, but again, if its just an emergency backup, keep it simple .
    Thanks - having had a 24v vehicle for a long time and tapping on of the 24v batteries is not an option - looked at this early in my ownership and the cost of hi amp equalizers is ridiculous.

    I will use a 24v to 12v converter but just interested if it will charge the battery as well (I could run a small 12v Dc Dc charger from the converter if needed) - afterall before smart chargers 240v to 12v battery chargers were just converters.

    Thanks

    Garry
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    I’m sure I have seen small 24-12v chargers on a few cranes I have worked on. 24v euro trucks, separate 12v system , with battery, on the crane to power the load management system. Maybe Redarc???
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    Quote Originally Posted by garrycol View Post
    provide 12v power to those thongs that need power when the engine is running.
    Electric thongs? Very good idea!
    Ron B.
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    Quote Originally Posted by p38arover View Post
    Electric thongs? Very good idea!
    Haha - auto correct gone wrong - can you fix it for me please
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    Quote Originally Posted by garrycol View Post
    Haha - auto correct gone wrong - can you fix it for me please
    Do you mean there are no electric thongs?

    transparent-light-up-strap-thong-kids-colorful.jpg_350x350.jpg

    I was hoping for the type of thong seen on a woman's backside, not on your feet.
    Ron B.
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    Quote Originally Posted by garrycol View Post

    So my simple question is would a 24v -12v 40 amp converter (not a charger) be able to charge a deep cycle battery in an emergency?
    The short answer is: "it depends". You need to know what the no load output voltage is and the device's strategy for dealing with over current loads. If it just blows a fuse it's not much good but if it is electronically limited to 40A it should be just fine. A no load output of 13.8V would be ideal.

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