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Old 08-16-2022, 09:23 PM   #1
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Question Individual DC-to-DC voltage converter for small loads

There are a few gadgets I want to use in my skoolie that come with a power brick to convert 110 volts AC to, say, 30 volts DC. Rather than plug the power brick into an inverter, it seems more efficient to convert 12 volts DC from my battery bank to 30 volts DC using a small voltage converter wired just to that one gadget. I recently bought one from amazon.ca:
https://www.amazon.ca/gp/product/B07WJ2G825/
and pictured here.
Question: is this a good approach? The relatively large heat sinks suggest some inefficiency. But Iím assuming itís still better than going through the inverter and power brick.
If you want to see this little converter in action, it comes up in a video I made on setting up a stereo at the front of the bus:
https://youtu.be/fE-_2s84GNU
starting at times 3:25 and 7:45
Thanks.
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voltage converter.jpg  

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Old 08-16-2022, 09:52 PM   #2
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I really like the thinking. I'm not experienced in these little devices but have also read they produce a lot of heat depending on what is being converted.

The loads on the 12 volt wire get large quickly, whereas running thirty feet of 15-2 at 120 volts provides so much more capacity with hardly any loss--after the inverter.

I think I've mentioned my 280 amp battery and 2000 watt inverter seems really capable of most things I do, so messing around with low voltage seems like an unnecessary complication.

But again, eager to see how it turns out and interested in learning more.
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Old 08-17-2022, 08:09 AM   #3
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Most dc-dc transformers, that increase the voltage, convert your DC into AC voltage to do so. So IMO you really won't gain much by installing these instead of using an inverter and then a power brick. The little you might gain I don't think would be worth the complexity. You can buy 12v-110v inverters at a large number of places. If you really want to be efficient, use an appropriately sized inverter to individually power each device you're installing.
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Old 08-17-2022, 08:14 AM   #4
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Best case for the efficiency scenario is if you know you'll be powering several devices that are a native 30 volts, is to design your battery bank at 30 volts as well. Then you'll have no conversion losses.

However, once you get away from standard 12/24/36 volts, your charging and inverter hardware gets rare/expensive.
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Old 08-17-2022, 08:39 AM   #5
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i bought at least 3 little 12v power converters that i recall, there may be a 4th.

only 1 is still working in the bus.

these were small 1" x 1" x 1.5" converters, sealed with some wires coming out.

i have a 12v to 19v that failed in 5 or 6 hours of use for my laptop.
i have a 12v to 6v that failed for an led strip, after a couple of months of use.
and i have a 12v to 24v thats still working, for a powered tv antenna i don't ever use.

i may have had more, but thats all i recall at the moment. 30% success rate as a long term solution.
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Old 08-17-2022, 01:42 PM   #6
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I can definitely see the potential for less loss assuming you use quality products sized appropriately. The question is how much, and at what cost in terms of money and trouble. Like Turf points out... There's plenty of junk out there. Think if it was me I'd start by using the included wall worts only when needed (switched to avoid always-on standby loads, or just manually unplugged), and see if you're so close to the wire in actual use to necessitate such measures.

That said, if its stuff that has to be on all the time, causing your inverter to stay up all the time too instead of spending some significant fraction of time in a reduced power sleep / monitor mode, that alone might make it worth the trouble. That's the very reason we went with both a 12v native modem/router, as well as Poe switch for our security cams. Taking those off AC allows our inverter to go into standby mostly all night long, and a good chunk of the day as well, where otherwise it would never have. Inverter self consumption can be a pretty big deal.
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Old 08-17-2022, 02:12 PM   #7
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Originally Posted by TheHubbardBus View Post
Inverter self consumption can be a pretty big deal.
This cannot be stressed or emphasized enough.

Especially your larger inverters, like most people like to get, as they can consume a noticeable chunk of your batteries--more than just about anything you plug in with a wall-wart power supply.
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Old 08-17-2022, 02:17 PM   #8
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Originally Posted by David from Ontario View Post
Question: is this a good approach?
If you're looking to to a DC-DC power box, I would highly suggest only using 12 VDC devices for this kind of thing, because otherwise you'll still be pulling the typical 10-20% xformer losses, but with a straight 1:1 xformer and maybe a power conditioning circuit, you shouldn't really have much of a loss at all.

I built a single power conditioner off my battery bank, and basically ran DC circuits all the way around and used the cigarette lighter plugs for everything that I can power off DC.
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Old 08-17-2022, 02:23 PM   #9
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Quote:
Originally Posted by turf View Post
i bought at least 3 little 12v power converters that i recall, there may be a 4th.

only 1 is still working in the bus.

these were small 1" x 1" x 1.5" converters, sealed with some wires coming out.

i have a 12v to 19v that failed in 5 or 6 hours of use for my laptop.
i have a 12v to 6v that failed for an led strip, after a couple of months of use.
and i have a 12v to 24v thats still working, for a powered tv antenna i don't ever use.

i may have had more, but thats all i recall at the moment. 30% success rate as a long term solution.
Yeah, reliability is a super important factor. These things rely on capacitors, and cheap versions are going to have cheap components like capacitors. If the device is relatively cheap and easy to find, buy scads of them as spares, and make sure they are readily swapped out.
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Old 08-17-2022, 02:25 PM   #10
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It's the Chinesium used in the manufacture of these.

I've still got some old "Made in the USA" 12V adapters from probably the late '90s that still work... though I doubt you could buy anything like that these days.
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Old 08-17-2022, 03:18 PM   #11
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Originally Posted by Albatross View Post
It's the [expression meant as a humorous reference to foreign manufactured products that some may take as an ethnic slur, intended or not] used in the manufacture of these.

I've still got some old "Made in the USA" 12V adapters from probably the late '90s that still work... though I doubt you could buy anything like that these days.
It's the consumer that drives quality. If people didn't buy the cheapest thing on the market but looked at quality as well we'd have fewer cheap, junky options on Amazon, Ebay and Alibaba.

People LOVE cheap.
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Old 08-17-2022, 03:42 PM   #12
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It's the consumer that drives quality. If people didn't buy the cheapest thing on the market but looked at quality as well we'd have fewer cheap, junky options on Amazon, Ebay and Alibaba.

People LOVE cheap.
Keep your non-ethnic-slur nonsense to yourself, man.

Pointing out that garbage made by effectively-slaves in other places has nothing to do with any kind of racism or -ist or anything else the SJW ree-rees like to get their panties in a twist over.

It is simply observed engineering prowess, over time.

The "Squarebody" GM/Chevy pickups were some of the greatest vehicles ever made, because every single part and component was over-engineered, and it was built simply and well. Likewise with your '90s Civics, even though most of the parts on them were relative crap, the Japanese put their best engineers into designing production and process instead of parts, so even though any individual component was made of cheap plastic, and would wear out, the cars themselves were notorious for hitting well over 300K miles if properly maintained.

Ze Germans are renown for being among the world's best engineers, but good luck working on anything they've designed, as it's generally quite the PITA to do (although I personally blame a bunch of bean-counters for the more recent developments).

There is nothing wrong, mean, or racist by stating that crap from China is less-well-designed and/or of poorer quality than things made elsewhere when it is a provable fact, with close to a century's worth of data points.

I'd still rather buy from China than Indonesia.
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Old 08-17-2022, 04:18 PM   #13
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lol

i am dating my self here but the 12v to 19v was the last thing i ever got from radio shack
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Old 08-17-2022, 04:47 PM   #14
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<snip>
There is nothing wrong, mean, or racist by stating that crap from China is less-well-designed and/or of poorer quality than things made elsewhere when it is a provable fact, with close to a century's worth of data points.

I'd still rather buy from China than Indonesia.
I don't want to make a big deal about it. It was a terrible expression, and thank God you didn't follow up with a similar one about Indonesians.

Like you, I call it as I see it. Good luck going forward.
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Old 08-17-2022, 04:50 PM   #15
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I don't want to make a big deal about it. It was a terrible expression, and thank God you didn't follow up with a similar one about Indonesians.

Like you, I call it as I see it. Good luck going forward.
But you are.

And I completely disagree--it's a fabulous expression that encompasses so much memetic magic in such a tiny little thing.

And Indonesian production quality is so bad, it has become very rare, and is thus not worthy of the time to craft such a clever and witty remark.
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Old 08-17-2022, 09:15 PM   #16
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Not worth the drama
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Old 08-18-2022, 05:26 PM   #17
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We will be running ALL our DC loads from a higher DC volt main though DC-DC converters. We'll be stepping down but the mechanisms are the same.
DC-DC converters use a transformer (probably have a chip these days as well). A pure transformer converter simply has two coils of wire sized appropriately for the job.
If there is no chip or circuit board (these days everything has one) then the converter can work in either direction. So lets say I want to change 24 volts to 12 volts. I build a transformer with half as many turns (plus a few for loss mitigation) on the output side. If I want to make 12 into 24 I put twice as many turns on the 12 volt side.....which means I can also simply switch the input and output of the 24 to 12 converter.
I teach this stuff to HAM radio students and operators.
So look up the specs for the device you're looking at (amazon won't likely have the specs you need).

Also, buy a unit larger than your needs because there will be less strain on the unit and so you can expect longer lifespan.
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Old 08-19-2022, 06:32 AM   #18
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How many watts to you need? Or amps at a given load voltage? All 12V loads? What DC mains voltage will you have straight from solar? 12, 24, 48vdc?
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Old 08-19-2022, 03:00 PM   #19
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Okay ignore everything in my last post about how DC to DC works. I must have been tired and I screwed it up badly. DO NOT pay attention to that part.
We will be doing higher voltage DC mains for purposes of voltage drop mitigation.
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Old 08-20-2022, 10:17 AM   #20
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Quote:
Originally Posted by Booyah45828 View Post
Most dc-dc transformers, that increase the voltage, convert your DC into AC voltage to do so. So IMO you really won't gain much by installing these instead of using an inverter and then a power brick. The little you might gain I don't think would be worth the complexity. You can buy 12v-110v inverters at a large number of places. If you really want to be efficient, use an appropriately sized inverter to individually power each device you're installing.

I bought such a device (different than this one).. and it did exactly that... had an inverter which converted 12 VDC into 12 VAC.. and the 1:3 transformer to take it to 36 VAC.. then that got rectified to 36 VDC and regulated down to 24 VDC... it seemed like a klougey china mess to me and a big waste...

there are a **LOT** better ways to do it .. using an amplifier IC and some smoothing caps you can get more efficient.. which some of the better devices uses.. but these are all pretty low current.. to do High current you are almost always going to have to have some drivers (power transistors of some sort)...which inherently make quite a bit of heat.. if I had the choice id use a higher voltage battery bank... esp if you are chatging it via solar or shore power.. charging by engine would obviously require much more work.
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