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12V DC to Variable DC, Off-the-shelf solutions?
#11
I have tested (and destroyed) several of those DC-DC converters from ebay.  Most of them get destroyed when ever I try to use them to charge 12V batteries . Or because they are not properly short circuit protected (shorts will easily happen when testing without standard sockets/plugs, but mostly just wires and crocodile clips). 
 
So my conclusion is, that most are not designed to be used in what could be referred to as "the automotive industry".

I have however been quite fond of the boards based on the LTC3780 chip. These boards have (so far) proved to be quite rugged. https://www.ebay.com/sch/i.html?&_nkw=LTC3780
They are automatic buck/straight/boost DC converters - and Julian Ilett has been inspired by the double H-bridge (around a coil) design concept, so he is (very slowly) working on making his own arduino controlled unit, as a super advanced buck/boost/mppt/pwm DC/DC manager/converter - but that is an entirely different story. 

Note: that LTC3780 boards come in two design variations, one with a slab of aluminium underneath, the other is just with some alu-wings glued on top of the mosfets.
Example  https://www.ebay.com/itm/253332046911  and  https://www.ebay.com/itm/192247767615

The boards keep very cool when only used as high as 2A, they get warm to the touch at 4A and they need more cooling if used above 4A. 

I have ordered some extra mosfets, as I intend to test to see if parallel soldering an extra set of mosfets might make the boards operate cooler, as I would like to be able to do 6-8A without extra cooling. And mosfets used in parallel greatly reduces the heat loss over the mosfet. 


So I think that the LTC3780 boards might be just what you are looking for, as they can be used at 12V battery voltages in, and produce any voltage out in the range of DC 1V-30V


Also note: That I have however noticed a largely varying degree of efficiency when used either as a buck or boost converter. But is a well known fact that boost converters are typically much less efficient than buck converters. 


I have also found that even though these Chinese boards appear to be similar, they might in fact be different board layouts/different production runs, as 1 in 3 of the boards I have, has not worked as intended out of the box/bag.  But the boards that do work, I am very happy with.
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#12
(12-28-2017, 08:30 PM)MrAlvinDude Wrote: I have tested (and destroyed) several of those DC-DC converters from ebay. (snip) So my conclusion is, that most are not designed to be used in what could be referred to as "the automotive industry".

I have however been quite fond of the boards based on the LTC3780 chip.
(snip)

Thanks for the wonderfully detailed suggestion.  I'll add this to my collection of possible solutions.
What doesn't kill me makes me smarter
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#13
The EXperts on this forum tell me I am doing it all wrong. I use a small sine wave inverter for my lap top and rechargeable tools. My battery bank is mostly happy with my small solar system. And I did not have to buy extra stuff for each device.
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#14
For down converting of DC voltages, I have moved to only using these MP1584 boards.
https://www.ebay.com/sch/i.html?_nkw=MP1584+3A

And because I use them in almost all of my experiments I usually order 10 boards at a time
https://www.ebay.com/sch/i.html?_nkw=MP1584+3A+10pcs


They are very efficient (typically  >95%) and the idle current is measured in uA.
They can manage 3 amp without getting hot.  It seems that the thermal monitor/shut down system only wants temperatures less than 50*C (122*F).

They are shout circuit protected.
But reverse polarity will let the blue magic smoke out instantly, so I often add an input diode, when used in systems/designs where reverse polarity input voltages might potentially happen.
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#15
Those LTC3780 boards look interesting...I had not seen them before. 

It looks like they might do what the OP is looking for, at least for lower power levels. 

Still, you might want to have a few of them around, in case of the occasional failure (smoke) mode. 

Most switching devices like this generate a large amount of RFI in the near field across a range of low, mid, and high frequencies...

Meaning they can interfere with a variety of receiving devices, like AM/FM radios, satellite radio, TV's, and of course, my personal favorite, ham radios. 

Still, I might want to do some experimenting with them....
Never trust a camp cook with lots of shiny new pans...
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#16
Don't you ever sleep? 
Huh
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#17
Definitely a fun science project!

Feel silly asking but you've seen these "universal" ones right?

https://www.amazon.com/dp/B01CFJH2U4

The DC5521 style plug with center positive is IMO best to use as "generic rosetta stone", can even get them with screw terminals.

Personally I think buying or making up a couple each for each device makes better sense.

Always start by asking the device mfg for a car adapter, especially when charging their batteries.
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#18
(12-28-2017, 10:06 PM)John61CT Wrote: Definitely a fun science project!

Feel silly asking but you've seen these "universal" ones right?

https://www.amazon.com/dp/B01CFJH2U4

Yeah those universal wall-warts have been out for 50 years or more, but its not a DC-DC converter.
Never trust a camp cook with lots of shiny new pans...
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#19
Sorry brain fart, can't find the receipt for the 12V ones I bought

https://www.amazon.com/gp/aw/d/B01BTR02DM
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#20
(12-28-2017, 11:18 PM)John61CT Wrote: Sorry brain fart, can't find the receipt for the 12V ones I bought

https://www.amazon.com/gp/aw/d/B01BTR02DM

lol..


Yeah 20 years or so on those...well ever since laptops and mobile internet anyway....

Wouldn't it be easier for them to just standardize the laptop plugs? I mean c'mon....imagine if all AC appliances had different plugs and all cities had different format AC sockets required in houses? 

What a mess that would be.
Never trust a camp cook with lots of shiny new pans...
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