Suggestions for a DC to DC converter (/charger) ?

e9999

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I'm intrigued by DC-DC converters but I don't have one. I'm thinking of getting one to play with and have around in case, not that I need it specifically for battery charging, but may use it for that possibly too.
Ideally I'd want something with a wide range of input voltages, say from a few (5?) volts to at least 24V and I would like to have full control over the output, like maintaining a constant voltage of my choosing over a wide range, and possibly choose from some battery charging schemes, ideally with full control of parameters.

Any suggestion as to some specific models that would do all that? TIA
 

sdnative

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What is the foreseen application? Does it have to be DC/DC? What about AC/DC?

I bought a bench power supply on ebay for under $50 that is capable of 0-18V DC and 5A (90W total). It can do constant current / constant voltage (CC/CV) which is suitable to charge batteries. Really handy to have around.

This is the model I bought, but there are lots of other brands and capacities. Cant go wrong with HP / Agilent if you can get one at a good price.
GW Instek GPS-1850D
 

e9999

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thanks, but I already have power supplies like that. And they are great to have around but this time I'm looking at DC-DC units specifically. The technology seems interesting so I want to learn a bit more about it. I did look a bit around but it seems like the ranges of voltage I was thinking about may be harder and more expensive to come by than I was expecting. Maybe I'm just unrealistic about that. I don't have a particular need for one although I can think of some applications of course, like charging a house battery or dealing with recalcitrant DC fridges, so mostly just hoping somebody may have one they are pleased with and that is versatile enough that I can try various things with.
 
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I would strongly recommend the product from Victron ( Orion Tr Smart DC-DC ), I must say that it is a very good and high-quality DC-DC charger. My current setup is
the following:
Orion Tr Smart DC-DC 12/12-30 ( Orion-Tr Smart DC-DC Charger Isolated - Victron Energy - https://www.victronenergy.com/dc-dc-converters/orion-tr-smart )
Liontron 100mAh smart battery ( Amazon product )

What I like about the Orion DC-DC is that it is possible to configure every aspect of it, for example, if you have a smart alternator then you could configure it to start charging at a certain voltage, the same goes for the engine shutdown detection. It supports charging to all types of batteries lifepo4 included. The battery I got is a bit overkill but I hope it will last a long time.

You could even configure different custom charging profiles if needed.


 

sdnative

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What kind of current do you need? May be hard to find something reasonably priced with a large voltage range capable of more than a few amps. The automotive converters like the Victron are great, but they can only accept a fairly narrow voltage range.
 

e9999

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yes, I had looked at the Victron Orion and it seems very nice. Main drawback for me is that the voltage ranges are narrow. I remember 8-17 on input and 10-15 out. I was hoping for wider, especially on the input side. They do have a unit with wider ranges, the Buck-Boost converter (IIRC) but that one is like 3x the price of the Orion.
I would definitely want several amps, maybe up to 10, say, so I can run a fridge comfortably with it.
 
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What you want will cost a lot - it's a niche requirement and will be priced appropriately. The moment you go buck-boost you're looking at a more complicated topology.

Then you want voltage from here to there on the input and here to there on the output and a lot of current at the output.

So, as a design it has to run from 'a few volts at the input' and then what? Boost to 12V or more and 10A? The input current can be very high - big inductors, big fets, big everything. The design spec is not realistic. You're trying to build a constant voltage, constant current power supply, but instead of a nice high 110VAC feeding it (bench use) you want it to run from down to 5V...

I design DC:DC converters for LED lighting applications and nailing down a realistic input voltage range and output voltage is the first step. Then agreeing to what the maximum output current will be and if it needs to be adjustable. You end up with combinations that can't be achieve without lots of expensive components (and size) for cases that may never be used. Then you need to worry about protecting the circuitry from situations that go beyond the power handling. i.e., the DC:DC converter may run from 8V to 50V input and output 10V to 80V and up to 4A, but no way can you run it from 8V and 80V output and 4A output... 320W output from only 8V input... super inefficient and you have 40A (more due to efficiency losses) at the input.

So, as much as you want it all, figure out what you actually need. If you can't figure it out, neither can a manufacturer...

Not sure what is 'intriguing' about a DC:DC converter, they just use an inductor or two or a transformer and take DC input and switch/pulse through the magnetics and then take the output and filter it back to DC. Even a little car USB outlet will use a DC:DC converter to more efficiently take 12V down to 5V.

cheers,
george.
 

e9999

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Good points, and yes, I'm trying to find out what is realistic to look for given what I'm prepared to pay for just having fun with some hardware. And I may need to narrow things down. But one can hope...

As to why it's intriguing, heck, anything that goes from a lower voltage DC to a higher voltage DC is magic...!
 
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^ no, it's not magic at all...

The DC gets pulsed (variable frequency/pulse width) into an inductor (magnetics), that can step up with one topology or down in another or with an H-bridge like switching structure to buck-boost and then filtered back to DC. Most DC : DC converters are running at hundreds of kHz or more. With high frequency the inductor size gets reduced as do the needed capacitors. Increase switching frequency causes increased losses in the switching elements (FETs), so there's tradeoff dealing with reduced size, but reduced efficiency. The fun of electronic design.

cheers,
george.
 

e9999

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o_O

Geez... Thanks, but I'll stick with Magic!
 
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Amazon has all kinds of buck and boost converters. Plenty good enough to play around with
 

e9999

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yes, and inexpensive too. Although most appear to be generic chinese stuff, and no charging algorithms. But so cheap that I may just get a good Victron for actual use and also one of the cheapos to play with and put a scope on and maybe take apart. Best of both worlds then.
 

e9999

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anybody knows if the Victron Orions allow you to limit the amps out? IOW, if I have the 12/12 30, say, will it always give 30A if the load calls for it or can I limit it to say 10A in the menus?
 
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anybody knows if the Victron Orions allow you to limit the amps out? IOW, if I have the 12/12 30, say, will it always give 30A if the load calls for it or can I limit it to say 10A in the menus?
I don’t see an option to limit the current on the Orions.

Go download the Victron Connect app. In the app they have a “Demo Library” where you can click though the settings on any device they make.
DF62D12D-1B4B-4E78-B7B4-D97E8F24DC70.png
 

e9999

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yes, I too don't see any settings in the demo for current limitation, but then again, I don't quite fully trust it to show all the actual app features either.

That said, some more googling seems to confirm so far that there is indeed no such feature.

Which is a bummer cuz I would like to limit the charging current unless I am really in a hurry. Better for the battery and less potential issues with cable sizes.

Maybe I should go with the 12/12 18 to limit the current to 18A which a typical 10AWG cable should handle easily. Can always add another one in parallel if I need more current.
 
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yes, I too don't see any settings in the demo for current limitation, but then again, I don't quite fully trust it to show all the actual app features either.

That said, some more googling seems to confirm so far that there is indeed no such feature.

Which is a bummer cuz I would like to limit the charging current unless I am really in a hurry. Better for the battery and less potential issues with cable sizes.

Maybe I should go with the 12/12 18 to limit the current to 18A which a typical 10AWG cable should handle easily. Can always add another one in parallel if I need more current.
It’s odd because almost all of their other devices have some way to adjust the maximum current.

I think even if you went with the 30amp version it’s still going to back down on the current the closer the battery gets to full.
 

e9999

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yes, of course, the current goes down close to full charge, but it looks like it will go full blast during the bulk phase, so that's not helping me if I would like a smaller max current.
 

e9999

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well, I ended up getting a Victron Orion for some battery tests I want to do. High quality build, as usual for Victron. Feels very solid.

One disappointment is that the V Connect app does not show the currents in or out. Maybe there is no current sensor in there. And no data logged either that I can see.

If anybody knows about those, is it OK to connect it to an ignition controlled input as in zero Volts when the ignition is off and full battery voltage when on? There is an input voltage lockout setting but that is probably intended for bad batteries and it's not clear what happens if the voltage goes below that. Or IOW, is the unit intended to be always connected to a hot battery on the input line, or will it not matter if the input goes to zero when ignition is off?
 

FrazzledHunter

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well, I ended up getting a Victron Orion for some battery tests I want to do. High quality build, as usual for Victron. Feels very solid.

One disappointment is that the V Connect app does not show the currents in or out. Maybe there is no current sensor in there. And no data logged either that I can see.

If anybody knows about those, is it OK to connect it to an ignition controlled input as in zero Volts when the ignition is off and full battery voltage when on? There is an input voltage lockout setting but that is probably intended for bad batteries and it's not clear what happens if the voltage goes below that. Or IOW, is the unit intended to be always connected to a hot battery on the input line, or will it not matter if the input goes to zero when ignition is off?
This is the exact scenario I have been doing for a couple of years now. I have a Victron Orion 12/24-15 to charge my Goal Zero Yeti 1500X right from the starter battery. I have not seen any problem connecting and disconnecting the Orion to the battery source which we often do when camping. I try and remember to turn the unit off before doing so, however.

We have our Orion set to Power Supply and leave it connected for the duration of our trip while driving letting the Orion stop and restart on its own as we stop and restart the engine. I might not be reading your post as you intended but it sounds like you’re also asking about how to set the lock-out and restart voltages.

These settings are for the safe use with your battery – they’re not necessary related to “bad” batteries. What you want is the Orion to turn on when the vehicle is running and to shut off immediately or within seconds after you turn the vehicle off. So I take a few measurements before we head out on a trip.

The charging and at-rest battery voltages are a bit interesting as they will vary by season (temperature), whether the engine is running and YOUR battery. I have the stock Toyota OEM battery as the starter and an AGM charged by a Redarc BCDC as my 2nd battery. The voltages are very different between the 2 batteries. Speaking specifically about the starter battery, voltages will be higher initially from the alternator when you first start and more so when it’s cold and lower on the battery when the engine is off, again more so when it’s cold. The alternator is a temperature sensing unit.

So I do the following seasonally:
  1. Let the vehicle sit overnight and measure the battery voltage with the engine off. This is your floor voltage. It will be lower in colder weather. You never want to draw you battery down below this voltage.
  2. Connect the voltage leads to the battery and start the vehicle noting the highest voltage immediately after starting. The alternator is at its peak voltage as it tries to top off the battery. As I mentioned, it will be higher in colder temperatures but will drop off as the battery charges. This is your ceiling voltage. This is mainly for info only and gives you a value to never exceed in your Victron settings.
  3. Measure the battery voltage with the engine running after running 10-20 minutes. I try to run an errand and measure the voltage in the parking lot of wherever I’m at LOL. This voltage will certainly be in-between your floor and your ceiling. I call this the running voltage. It always has been for me.
There is a 4th voltage you can get if you’re over-analytical like me and that’s the battery voltage immediately after you turn off the engine. It will be above the floor voltage but not my much, in my experience.

By now you should have a nice warm fuzzy feeling as to how your electrical system is performing. So I set my Victron voltages at or just above the floor voltage (#1) and just below the running voltage (#3).

The actual voltages I have right now in my Orion with an OEM Toyota Lead Acid battery and alternator are as follows:
  • Lock-out value: 12.3V
  • Restart value: 13.2V.
The Orion turns off literally within seconds after I stop the engine. It’s what I want, it works really great.
 

e9999

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thanks for the detailed information. Sorry, I wasn't clear, and also used the wrong terminology, my mistake. When I said "bad" battery I meant to say a battery that was very much discharged, like 7V (the default for the undervoltage protection). I also used the term "lock out" wrongly, I meant to say *undervoltage*. "Lock out" is for engine detection I think. Dang, too many parameters... (or good...)

Anyway, what I'm wondering is what happens if the Orion sees an input of zero volts without it being turned off first. That is possibly very different from it going to sleep so to speak (as in output deactivated), because of the lock out threshold or the engine detection threshold while there still being some voltage seen at the input and the Orion keeping an eye on things. More specifically, I'm wondering what would happen if the Orion is in the back with a house battery and connected to a bus that goes to zero volts when the ignition is turned off, and then suddenly sees over 12V again when I start the engine. Any chance that would damage it? The reason I brought up the undervoltage feature is that it seems (a guess) like the unit will actually completely turn off below that threshold (the 7V default) so I'm hoping that if it does that it won't hurt anything at a full zero input either. And if it's fine with zero input, will it reactivate when the voltage goes back up? I'd try it on my bench, but I'd rather not zap a brand new costly unit without a bit of research first.

Unfortunately, I think Victron has now gone more mainstream in that they did not respond to my last technical inquiry besides "contact the distributor". I had been telling folks earlier that they were great at answering questions. Not so much any more maybe, sadly.
 

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