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Old 23-07-2017, 19:50   #1
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How do I step down from 36 volts to a USB voltage?

I'm trying to tie-in to a higher voltage battery for lights and phone charging. I have access to the 36V at the charging port. I want to take that to a lower voltage in a lightweight and weatherproof manner. Open on cost so I'm looking for the best way to go about this build.
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Old 23-07-2017, 23:16   #2
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Re: How do I step down from 36 volts to a USB voltage?

Go down to (a) 12V circuit(s), everything from there is very reasonably priced.

Samlex is decent value, look also at Victron, MasterVolt too pricey IMO.

I think the Victrons can also act as a 12V battery charger, but not Samlex's.
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Old 24-07-2017, 03:27   #3
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Re: How do I step down from 36 volts to a USB voltage?

They sell thousands of DC-DC buck converters on Ebay, many under $2. Just type in the voltage and current requirements.
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Old 24-07-2017, 07:25   #4
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Re: How do I step down from 36 volts to a USB voltage?

Like socaldmax said. The only problem is going to be that the really cheap ones seem to top out at 30 volts for input. You also need to be aware of how many amps you intend to pull through the circuit. A lot of the really cheap ones top out at 1.0-1.5 amps. If you want max charging on a USB circuit you need one that goes to at least 2.0 amps, and 2.5 would be better. Or more, if you want to charge multiple devices at the same time.

In any case, here's an example of one that goes up to 40 volts for input, and provides up to 12 amps of current, and it's only $8.59...
DC-DC CC CV Buck Converter Step-down 7-40V to 0.8-35V 12A Power Supply Module | eBay

If you need less current you should be able to find one for even less money. I found this on ebay by searching for "dc buck converter 40v".
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Old 24-07-2017, 07:46   #5
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Re: How do I step down from 36 volts to a USB voltage?

Thank you all very much. I was searching without enough knowledge to interpret the results. My battery source is an electric bike battery. I will run white and red LED bike safety lights along with an iPhone charger. If anyone has suggestions on components for a working design I'll put them together and share pics.
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Old 24-07-2017, 07:51   #6
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Re: How do I step down from 36 volts to a USB voltage?

Cheap bare-board stuff from China is great for non-critical fooling around on land, but I would recommend going for an already sealed/boxed unit from a trusted known vendor, for anything electric on a boat.

But that's me.
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Old 24-07-2017, 08:01   #7
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Re: How do I step down from 36 volts to a USB voltage?

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Originally Posted by john61ct View Post
Cheap bare-board stuff from China is great for non-critical fooling around on land, but I would recommend going for an already sealed/boxed unit from a trusted known vendor, for anything electric on a boat.

But that's me.


I'm with you on that. Open budget for quality on this build.

Any specific high-quality component suggestions around "converter", lights, USB charging port?
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Old 24-07-2017, 08:36   #8
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Re: How do I step down from 36 volts to a USB voltage?

How about this one?

DZS Elec DC 6V-40V 9V/12V/24V/36V to 5V 3A Double USB Output with LED Digital Display LM2596 Buck Voltage Converter with Heat Sink Charger DIY USB Power Supply https://www.amazon.com/dp/B071776Q5C..._jxGDzb5CTCJMJ
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Old 24-07-2017, 09:22   #9
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Re: How do I step down from 36 volts to a USB voltage?

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Any specific high-quality component suggestions around "converter", lights, USB charging port?
Already gave the converter, just a question of sizing for current, 25A is less than 70A, and Victron IMO better than Samlex.

Avoid standard ciggie ports like the plague, Blue Sea makes a better twist-lock version that also is backward-compatible to standard plugs, I think carry up to 16A each. https://www.bluesea.com/products/cat...0/USB_Chargers

Any higher draws use Anderson plugs.

Euro DIN style (Powerlet/Hella/BMW) are also nice, but then the USB plugs to fit are​ $30+ each.

Ciggie adapters for the last two are also available for standard 12V USB plugs.

You could also hardwire the USB ports around the cabin, but then when the Thunder/type-C, whatever new hotness, comes around every few years you need to replace.
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Old 24-07-2017, 09:25   #10
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Re: How do I step down from 36 volts to a USB voltage?

LED lights are a separate issue, if your converter outputs say 13.8V, test to get ones that don't run too hot. Or put them on a separate dimmer circuit, specialized stuff there.
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Old 25-07-2017, 13:41   #11
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Re: How do I step down from 36 volts to a USB voltage?

for $5 this will solve your problems... (this is the first I managed to find... 2596 DC-DC Voltage Step Down Module - Green (DC 5~36V) - Worldwide Free Shipping - DX

gives you 2 amp running.. up to 3 amps...
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