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36V step down to 12V/20A for two pairs of LED’s

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Hammer335i

Hammer335i

Structural
Jan 25, 2011
21
I am not an electrical engineer but I took a few circuit classes in college 20 years ago đŸ˜‚. Before I burn up some very expensive LED’s can someone please check my work?

Here is the situation: I have a 36V/63Ah LifFePo deep cycle marine battery that I need to connect to four 12V/10A LED’s on my boat. I will put two LED’s on the port side and two on the starboard side. So I was thinking of splitting the leads off the battery and putting a voltage regulator to step down to 12V/20A for each side (port & starboard). Then each side will split again to a forward and aft LED.

Please see attached circuit diagram and let me know if you think this will work!

Thank you in advance!
 
 https://files.engineering.com/getfile.aspx?folder=ec39e5a4-5dce-4377-9e9a-d0932ef01996&file=86ABC3E5-D8B6-47C5-BFB2-A18ECA6F2F54.jpeg
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Oh and one more question: since this is a 63 Ah battery and I am burning 4 x 10A LED, does that mean this thing will only run for an hour and a half?
 
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A DC/DC convertor can step down the 36 volts. Digi-Key has a nice selection page. I'd protect the LEDS with current limiting resistors and zeners (you'll need something higher that a 12 volt output then). Select a convertor that will operate down to about 12 volts or so for the input. That will keep the LEDs at full brightness as the battery voltage drops.

Not sure about the Ah rating. I'm guessing the voltage will drop to 12 volts at about 36/12 x 1 hour = 3 hours.
 
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You basically need a DC/DC buck converter. The 'YIPIN HEXHA' DC/DC converter of your amazon link may do the job. I don't recognize the name. The 96% efficiency they advertise is typical of a buck converter. They are using the term 'transformer' loosely to imply 'voltage converter' and not electrical isolation. For something that is probably made on-the-cheap I wouldn't trust it at the full 20A of output.

From a 36V, 63Ah battery you should expect 3X the Ah at 12V, times the 0.96 efficiency for running your 40A of lights.
 
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You should link the LED luminaire specs, because chances are it has a DC-DC regulator built in already which may present other options.
 
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> this is a 63 Ah battery and I am burning 4 x 10A LED, does that mean this thing will only run for an hour and a half?

DC 36V/48V Step Down to 12V 20A 240W DC DC
No. But it does mean one 12Vout converter can only power 2 Lamps

A total power of 480W out load might need 530W input or so to the converter allowing just over 10% loss being conservative.

In theory, a new battery rated at 63Ah @ 36V can output 63*36= 2268 Watt-h or 530 W for just over 4h.

 
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Are you certain the LEDs are rated for 10A? That's quite a large LED. LEDs produce about 5x light for the same wattage as incandescent, so these 12V/10A LEDs would be the equivalent of about 600W.

Here's some ideas that might be simpler.

1. You can run three LEDs in series and not use an inverter.
2. Install a 12V car battery and keep it charged. Use that for your LED circuits.
 
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