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This project is on my boat which has 3 Group 27, 12V batteries in series which is my house power source.

I want to power approx. 510 LED lights from my 12V house batteries. The lights are taken from several string lights originally part of a system consisting of approx. 100 lights powered by a rechargeable 3.2V 300mAh battery and a small solar panel. I intend to discard the batteries and solar panels and connect these strings together to form 1 string.

My thought was to use a DC-DC Converter 12V to 3.3V, 3A max step down voltage regulator transformer (DROK 090601).

I am not an electrical engineer and am looking for concurrence or guidance on a workable design.

Thank you in advance for any advise offered.

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    \$\begingroup\$ To advise is the verb, advice is the noun. Now you know :) \$\endgroup\$ – Daniel Tork Aug 6 '18 at 15:00
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    \$\begingroup\$ I don't really understand your problem. How many 12V batteries do you have? What strings are those? I think some clarification is needed before anyone can help you. \$\endgroup\$ – Daniel Tork Aug 6 '18 at 15:08
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    \$\begingroup\$ Arrange LEDs in series parallel arrays to match supply voltage with current limiter. Define LED specs or links including battery total voltage \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 6 '18 at 15:28
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    \$\begingroup\$ If you have a 12 volt electrical system, your batteries are in parallel, not series. A series connection would give you 36 volts. \$\endgroup\$ – Peter Bennett Aug 6 '18 at 15:29
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Sounds like a great little project. Use that DROK 12v to 3.3v converter, and treat each of the 100 light strings as a single 3.3v load, so wire those 100 light strings in parallel with each other.

It may look physically look like 1 string composed of 5 strings in series, but don't let that confuse you. The strings should be wired in parallel with each other, even if that takes more wire. Each string has a single 3.2 v+ and Ground or v- connection. All the 5 strings' v+ should be wired together and connected to the DROK 3.3 V+ output, and all the 5 v- also connected together and to the DROK V-.

To save wire, if each 100 LED string has the v+ and v- connection at only one end, then get some 2 conductor stranded speaker wire and fasten it physically along each string to bring the v+ v- pair to the other end that needs it. Then the next string can connect to that pair of v+ v-, and so on for each string.

If you want any of the 100 led strings to be physically separate from the others, make a "3.3v extension cord" of the needed length of speaker wire and run it directly from string to the DROK output.

When you add switches, let each switch 1 or more whole 100 LED strings.

If those 300mah batteries would light a string for about 3 hours, each string draws only 100ma. Your 3A buck converter could theoretically handle 30 such 100 led strings.

Perhaps I'm saying the obvious. Good Luck!

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  • \$\begingroup\$ Mitch, The string lights are connected together in parallel. I would prefer to simply connect the strings together (eliminating the battery and solar panel for each string) to act as one string and then connect to my 3 house batteries (connected together in parallel?). I presume that a converter/resistor would be required to reduce the Voltage to a level that would be acceptable to illuminate all 510 LED lights. I am looking for guidance on what converter/resistor could be used to reduce the voltage from 12V to a workable voltage. I would wire all 510 LED lights to one switch. \$\endgroup\$ – Don Helgeson Aug 8 '18 at 13:14

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