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Old 15-01-2020, 03:10   #1
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DC to DC 12v output

Hi all
I want to find some good quality DC to DC converters for permanent install ( not cigarette lighter power socket ones )

I want a fixed 12v output from my battery supply which can go fairly high when charging on the solar panels.

I fried a nice low power fan and don't want to do that again!

a nice low amp draw would obviously be important.

many thanks
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Old 15-01-2020, 03:39   #2
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Re: DC to DC 12v output

Hi,
I've been using this kit for some years
DCDC-USB, Intelligent DC-DC converter with USB interface
Started with their 12/12 units ... currently have a couple like above running Macbook/ LG screen/Asus computer that need 18/19V

Good stuff...
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Old 15-01-2020, 04:06   #3
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Re: DC to DC 12v output

That looks very interesting, many thanks.
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Old 15-01-2020, 04:28   #4
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Re: DC to DC 12v output

There are devices from companies such as Mastervolt, Victron etc that will do what you want (see link below).

They are more expensive than the non-marine alternatives. I think these are overkill for most applications, but they are isolated (some models), robust, reliable and designed specifically for the application, so they are worth considering for critical systems.


https://www.mastervolt.com/products/...agic-12-12-20/
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Old 15-01-2020, 04:35   #5
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Re: DC to DC 12v output

How much current will you draw? Plenty cheap buck/boost converters on ebay OK for a few amps which will give constant 12v out from varying input voltage.
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Old 15-01-2020, 05:21   #6
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Re: DC to DC 12v output

Quote:
Originally Posted by mtompson View Post
I want a fixed 12v output from my battery supply which can go fairly high when charging on the solar panels.

I fried a nice low power fan and don't want to do that again!
Hi - how high does your battery voltage go when you're charging on solar? I'm surprised that it could go high enough to fry something intended to be used on a boat's 12v. Might be a battery issue, or something to do with where the solar power feeds into the 12v system.

If it's just a few devices that need a tightly regulated 12 v, it might be cheapest to buy small DC-DC converters for just those.
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Old 15-01-2020, 06:21   #7
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Re: DC to DC 12v output

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Originally Posted by conachair View Post
How much current will you draw? Plenty cheap buck/boost converters on ebay OK for a few amps which will give constant 12v out from varying input voltage.
only a few hundred ma, nothing too big. Very low power draw PC fans.
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Old 15-01-2020, 06:25   #8
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Re: DC to DC 12v output

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Originally Posted by Lake-Effect View Post
Hi - how high does your battery voltage go when you're charging on solar? I'm surprised that it could go high enough to fry something intended to be used on a boat's 12v. Might be a battery issue, or something to do with where the solar power feeds into the 12v system.

If it's just a few devices that need a tightly regulated 12 v, it might be cheapest to buy small DC-DC converters for just those.
agree with the suprise, but I want to run a few large(ish) PC fans, some of the very low power draw super quiet ones like the Noctua fans. So, not 'intended for use on a boat' and I guess pretty sensitive. ( it was one of those that went )

The converters you linked to look good, thx
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Old 15-01-2020, 06:32   #9
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Re: DC to DC 12v output

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Originally Posted by mtompson View Post
only a few hundred ma, nothing too big. Very low power draw PC fans.
Loads on ebay then, buck/boost - worth doing some research though, the really cheap ones can be RF noisy. As can the expensive non-ebay ones....
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Old 15-01-2020, 06:39   #10
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Re: DC to DC 12v output

For that low current, the little sealed up units are very robust and cheap on both eBay & Amazon, even more so from Ali or banggood

https://www.amazon.com/KNACRO-Waterp.../dp/B01IAQFUEQ

Keep under 80% of rated max watts will last forever.

Even cheaper chinese, better to buy spares and test, some are grossly overrated even 50% needs cooling.
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Old 15-01-2020, 06:45   #11
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Re: DC to DC 12v output

thx all, really helpful, got some great links and good tips. The high spec PC fans are not that cheap so I'll be glad to protect them. (They're great fans though)
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Old 15-01-2020, 10:17   #12
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Re: DC to DC 12v output

what kind of controller are you using with your solar panels? The higher and variable voltages coming out of your panels shouldn’t be seen on your 12Vdc (nominal) electrical system.
Adding a set constant voltage DC-DC converter may make lots of sense, but I would check the solar panel controller for proper
operation
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Old 15-01-2020, 10:24   #13
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Re: DC to DC 12v output

Possibly overkill for this application, but I use these: https://www.victronenergy.com/dc-dc-...rters-isolated


Allan.
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Old 15-01-2020, 10:27   #14
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Re: DC to DC 12v output

@AndyEss, Genasun, up to the normal 14.5v(ish), but I fear that may have been too much for the delicate fans.
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Old 15-01-2020, 10:45   #15
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Re: DC to DC 12v output

There are also "DIY UPS" devices from Samlex and others, where you give the sensitive-gear circuit its own smaller standby battery, which is constantly Float charge kept topped up.

Normal operations the loads draw a filtered current from the main sources / bank upstream.

Soon as that power runs out or is cut for whatever reason instantly switched to the "UPS" battery, able to keep running long as you sized that batt for. One-way flow only.

Great for safety/security, nav gear, comms etc

or even a Starter when alt output has been rewired to House.
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