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Old 16-05-2018, 10:29   #1
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24v to 12v

I don’t seem to find an answer on this question so here goes.
I want to install a 24v battery and solar system on my vessel. Use a step down regulater to run all the 12v systems on board. Question, what is the current draw of the 12v system from the 24v system? And let’s say a pump drawing 10 amps at 12v, what will be the amps drawn from the 24v system?
The plan is to change the system slowly over to 24v as electrical systems reach their end of life.
Reason for changing over to 24v, less power being used overall from a 24v system. The 12v wiring harness in the vessel will easily be able to handle the 24v since it’s designed for 12v with less power losses in the wiring in the end.
Hope my reasoning isn’t to bad on this. Any help will be appreciated and if there is already a thread discussing this, just point me to the relevant answers.
Thanks.
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Old 16-05-2018, 10:42   #2
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Re: 24v to 12v

Youíre going to cut the current in half. So 10amps at 12volts becomes 5amps at 24volts.

However you say you want to do this as you will use less power overall. This is not true, youíre still isi g the same number of watts.....maybe not loosing as much to transmission losses, but that amount is marginal unless youíve got really long wire runs
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Old 16-05-2018, 10:51   #3
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Re: 24v to 12v

my solution is this a 24 to 12volt 12amp battery charger
https://www.alfatronix.com/dc-dc-battery-chargers

my solar is 24v 500w with 2x110ah agm,but house is 12v with 225ah fla as the engine is 12v .
the 24v keeps the 12v batteries fully charged all the time.
i may increase the 24v system with 2 more 110ah agms as i run the inverter off the 24v as well
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Old 16-05-2018, 10:52   #4
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Re: 24v to 12v

Well, I don’t think I express myself so clearly. The 24v system seems a bit more efficient that I use at present. Taken, it is a system that runs everything on 24v. The new vessel I get is 12v and need new batteries and solar panels that I have on my current vessel. The plan is to move it over and then use a step down regulator or transformer to convert the 24v to 12v to run all the systems. And then as described above, change it over to 24v as electrics get to their end of life. What are the power losses doing this? Is it significant and the amphours drawn out of the 24v batteries, will it be less than from the normal 12v system?
The batteries are 8 * 6v * 180ah charged by 1000watt * 24v solar panel. Batteries are 2 banks of 24v.
Hope this clarify things a bit.
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Old 16-05-2018, 11:04   #5
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Re: 24v to 12v

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Originally Posted by Atlantech View Post
Well, I donít think I express myself so clearly. The 24v system seems a bit more efficient that I use at present. Taken, it is a system that runs everything on 24v. The new vessel I get is 12v and need new batteries and solar panels that I have on my current vessel. The plan is to move it over and then use a step down regulator or transformer to convert the 24v to 12v to run all the systems. And then as described above, change it over to 24v as electrics get to their end of life. What are the power losses doing this? Is it significant and the amphours drawn out of the 24v batteries, will it be less than from the normal 12v system?
The batteries are 8 * 6v * 180ah charged by 1000watt * 24v solar panel. Batteries are 2 banks of 24v.
Hope this clarify things a bit.
stepdown transformers draw power even when idle
they also stop working,which would disable your 12v system
high loads like a 12v anchor windlass will need to draw from a 12v battery
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Old 16-05-2018, 11:08   #6
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Re: 24v to 12v

Are you talking about moving your solar panels and batteries over?

If thatís the case, imho youíd be better off re-configuring the batteries to 12v, keep the solar panel, and change to a 12v mppt regulator
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Old 16-05-2018, 11:17   #7
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Re: 24v to 12v

Thanks for the answers. Iím pretty new on this forum, brand new actually and still finding my feet here. One of the options Iím looking at is to, as suggested, use the 24v panels with mppt controller to the 12v batteries I can configure. What is the amperage Iíll get out of the controller then?
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Old 16-05-2018, 11:25   #8
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Re: 24v to 12v

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The plan is to move it over and then use a step down regulator or transformer to convert the 24v to 12v to run all the systems. .
I think you will find that lots of 12v electronics will run quite happily at 24v, certainly all my Garmin stuff did on a previous boat. The portable Waeco fridge freezer was another that operated much better at 24v, even managed to freeze my sandwiches the first time out with a bit of enthusiastic use.

The only thing I couldn't find was an VHF radio that would run 24v, the normal yacht ones seem to be 12v only.
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Old 16-05-2018, 11:33   #9
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Re: 24v to 12v

Quote:
Originally Posted by Atlantech View Post
Thanks for the answers. Iím pretty new on this forum, brand new actually and still finding my feet here. One of the options Iím looking at is to, as suggested, use the 24v panels with mppt controller to the 12v batteries I can configure. What is the amperage Iíll get out of the controller then?
double the amps for 24v and more amps on cloudy days at 12v
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Old 16-05-2018, 11:46   #10
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Re: 24v to 12v

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double the amps for 24v and more amps on cloudy days at 12v
So, if I get this right, my 1000watt panels will give me 41 amps, best case scenario. With mppt controller Iíll then get output of 12v and 80 amps. Again, best case and perfect world.
What size controller do I need then? One rated to 80 amps or more?

Seems the way I need to go, after everything taken into consideration.
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Old 16-05-2018, 11:56   #11
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Re: 24v to 12v

Quote:
Originally Posted by Atlantech View Post
So, if I get this right, my 1000watt panels will give me 41 amps, best case scenario. With mppt controller Iíll then get output of 12v and 80 amps. Again, best case and perfect world.
What size controller do I need then? One rated to 80 amps or more?

Seems the way I need to go, after everything taken into consideration.
you need to check what the maximum rating is for the panels,which may be nearer 50a,but most solar chargers are rated in watts so get one that exceeds 1000 watts of panels. and will automatically detect voltage of batteries.
so will normally be a 12v/60v unit rated at +-1200w

not sure what country you are in but i could list a few suppliers here in the uk for suitable PWM or MPPT controllers
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Old 16-05-2018, 15:53   #12
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Re: 24v to 12v

Thank you for all the replies. I know now what direction to follow. I havenít thought of all the heavy equipment. Windlass, engines etc. Will keep it 12v and just get right controller. Seems simplest way forward.
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