Switching from 12V to 24V

[john61ct]

Originally Posted by ka4wja

why in the world would you want to use a voltage regulator, to get from 24vdc to 12vdc, and get 50% eff at best??? (I mean if you needed 12vdc at 5amps, etc., you'd take 24vdc at 5 amps just to get that 12vdc at 5 amps...)

You're right, that would be stupid*, if that is how that type of converter works.

But, is that **really** how this type of converter works?

http://www.ykpowersupply.com/product_show.asp?id=4659

Vendor claims over 90% efficiency!

You weren't talking about solid state switching converters right?

But old-school linear voltage regulation.

Wiki says the two main modern types are

switched capacitor /*"charge pump" converters for low ampacities, and
switch-mode converters for higher currents

______
* unless for just a few, very low-AH/day devices unavailable at reasonable cost in 24V

[noelex 77]

Originally Posted by ka4wja

But, since the argument for using 24vdc is for better [sic] energy efficiency, why in the world would you want to use a voltage regulator, to get from 24vdc to 12vdc, and get 50% eff at best???

The marine 24/12v such as Victron are around 95% effecient with an offload current of around 0.015 A so you do not need to be too worried about effeciency losses. Reducing voltage is not electronically difficult to do.

In Europe the Victron 24/12 v converters are around $24 for a 10A unit and around $100 for a 25A unit. So you don’t need to be too worried about cost, even going for a marine rated voltage convertor rather than a generic version.

Every 12v boat has a multitude of voltage conversion circuits that reside inside equipment, as well as external devices such as usb sockets (12v to 5v) laptop power supplies (12v to 19-21v) inverters (12v to 110-230v) etc so the addition of one extra is not a great deal of potential additional RF noise.

One advantage of the 24/12v converters is they supply a stable voltage supply and most units will deliver 13.2 -13.8v, which reduces the problems associated with voltage drop. So together with the reduced wiring size there are advantages as well as drawbacks.

However, I think we are in agreement that the secret is to have very little running from 12v and this is easily accomplished. Only a few devices will need 12v with modern marine equipment.

[john61ct]

Originally Posted by ka4wja

if you want a 24vdc boat....then you design and build a 24vdc boat....you do not need to use 12vdc for much of anything...

But the problem is, some very large current devices do **require** higher voltages.

And hundreds of product categories are readily available and cheap in 12V, but

**lots** more expensive or even impossible to find in the higher voltages.

So for those avoiding inverters as much as possible,

either cost effective energy efficient low-RFI converters, or

running a small 12V bank

does become necessary.

And neither is really difficult nor that expensive.

[noelex 77]

Originally Posted by john61ct

And hundreds of product categories are readily available and cheap in 12V, but

**lots** more expensive or even impossible to find in the higher voltages.

John, this was true a decade or so ago, but there is very little that is not available in 24v these days. We have a reasonably electrically sophisticated boat, but there are only two devices running from 12v.

Perhaps you could give examples of the ”**lots**” of devices that you are concerned are not available (or are significantly more expensive) in 24v versions.

[ka4wja]

John, et al,
Yes, I of course was referring to the comment about using a simple 7812 voltage reg (with some pass transistors, that will also have some eff loss)...and stating that that approach would be useless from an efficiency stand point....
Not talking about modern switch-mode voltage converters (which are DC-AC-DC inverter/converters)...

Guess I shouldn't be on here when I'm supposed to be working...

Gotta go!

John

[CatNewBee]

Originally Posted by ka4wja

John, et al,
Yes, I of course was referring to the comment about using a simple 7812 voltage reg (with some pass transistors, that will also have some eff loss)...and stating that that approach would be useless from an efficiency stand point....
Not talking about modern switch-mode voltage converters (which are DC-AC-DC inverter/converters)...

Guess I shouldn't be on here when I'm supposed to be working...

Gotta go!

John

well, it depends. Of it is about powering a n2k bus or some leds losses are not really relevant, so for small devices linear voltage regulators are just fine.

[john61ct]

Originally Posted by noelex 77

John, this was true a decade or so ago, but there is very little that is not available in 24v these days. We have a reasonably electrically sophisticated boat, but there are only two devices running from 12v.

Well I'm not talking about marine gear,

nor sophisticated, that to me implies lots of inverter based usage.

Just cheap utility / household gadgets, ICT and audio / video gear,

say an immersion blender, CPAP, vacuum, spice grinder, recharging tool batteries.

Putting in a subsidiary 12V circuit is just NBD for me, no reason to try to be a purist about a voltage level.

That is, if going to a higher voltage is even required, which so far in my use cases I have not come across,

other than maybe an ultra-efficient 48V aircon unit, currently unaffordable for me anyway.

[john61ct]

Originally Posted by ka4wja

Not talking about modern switch-mode voltage converters (which are DC-AC-DC inverter/converters)

My understanding is the device / line I linked to are not that.

[tarian]

to much over thinking for a battery system , this is not a nuclear plant , a simply 30 amp 24 v to 12 volt converter , is what I use no issues with voltage drop
, no issues with noise , no electric interference , 3 items on my 12 volt panel , one is the stereo.
if building a boat form scratch and a boat over 40 ft then it is a good consideration to go 24 volts in regards to the cost saving , voltage drop , and thickness of wires.

[coopec43]

"I LOVE READING THIS STUFF IT IS VERY FUNNY.

Reality............

All the top Aussie teams run 24v through 12v motors.

Most expect a life expectancy of somewhere around 18months to 2 years from there motors.

Tjhe difference is they service there motors regularly, blowing out the carbon dust etc...

There winching is very voilent and extremely hard. The reason they use 24 through 12 is that it is like Nitro charging your winch, it will pull like hell and never give in and at great speed.
What actually kills the motors is over revving. This usally occurs when winching cable out of load.
The Aussies have got over this by using free spool systems, however there are people that don't.
Paul Wightman has been running 12v Xp's with 24v going through them for over a year with no troubles and they are still has fit as the day he fitted them.

The only really usefull bit of info in this thread so far is the person that wrote "Flat batteries kill motors" this is correct.

Three of our Twins have just done the Rain forest challenge unfortunately all the teams had to be rescued and 50 cars left in jungle due to severe monsons and flooding, but those using 24 through 12 suffered no problems and were amazed at what they where having to pull through just to stay out of danger.

So there it is, Yes you can. But do remember to pulse the out button if you are paying out. If you want to see how quick they are i recommend watching the Alpine challenge 2007, where almost all the cars were using twin motor setups (either ours or Wazzas) resulting in 5 of the top 6 places for us and ALL including the rest of the top ten using 24 through 12.

Doing stuff that most would call impossible and almost ALL will never do.
Waiting for the fun to start :lol:
Jim

Sorry forgot to say.............
The motors do not get over hot doing this either, we have found that they stay cool to medium temp 125ft long pulls

However if the batteries get low.......The heat builds up very quickly.
I have run 24 through 12 myself many times, but i must tell you that i have destroyed motors by over revving them.
I however have NEVER destroyed one by over heating or burning out."

Jim

https://forums.lr4x4.com/topic/20463-12v-winch-24v/

[DeValency]

Originally Posted by coopec43

"I LOVE READING THIS STUFF IT IS VERY FUNNY.

Reality............

All the top Aussie teams run 24v through 12v motors.

Most expect a life expectancy of somewhere around 18months to 2 years from there motors.

Tjhe difference is they service there motors regularly, blowing out the carbon dust etc...

There winching is very voilent and extremely hard. The reason they use 24 through 12 is that it is like Nitro charging your winch, it will pull like hell and never give in and at great speed.
What actually kills the motors is over revving. This usally occurs when winching cable out of load.
The Aussies have got over this by using free spool systems, however there are people that don't.
Paul Wightman has been running 12v Xp's with 24v going through them for over a year with no troubles and they are still has fit as the day he fitted them.

The only really usefull bit of info in this thread so far is the person that wrote "Flat batteries kill motors" this is correct.

Three of our Twins have just done the Rain forest challenge unfortunately all the teams had to be rescued and 50 cars left in jungle due to severe monsons and flooding, but those using 24 through 12 suffered no problems and were amazed at what they where having to pull through just to stay out of danger.

So there it is, Yes you can. But do remember to pulse the out button if you are paying out. If you want to see how quick they are i recommend watching the Alpine challenge 2007, where almost all the cars were using twin motor setups (either ours or Wazzas) resulting in 5 of the top 6 places for us and ALL including the rest of the top ten using 24 through 12.

Doing stuff that most would call impossible and almost ALL will never do.
Waiting for the fun to start :lol:
Jim

Sorry forgot to say.............
The motors do not get over hot doing this either, we have found that they stay cool to medium temp 125ft long pulls

However if the batteries get low.......The heat builds up very quickly.
I have run 24 through 12 myself many times, but i must tell you that i have destroyed motors by over revving them.
I however have NEVER destroyed one by over heating or burning out."

Jim

https://forums.lr4x4.com/topic/20463-12v-winch-24v/

*****

Well, I guess, some of us still prefer to sail and fix the necessary things on and under board rather than burning electric motors by running at 200% of the rated voltage.

But in that other southern end of the world, maybe things are really different...

[ka4wja]

A few quick comments / clarifications / answers...


1) I'm not going to go as far as tarian here, regarding Star Trek, and nuclear plants (and I do still caution all to be aware of RFI issues with voltage converters, particularly those with HF radio, Ham, SSB, WeFax, PACTOR, Sailmail, etc.)....but he made an excellent point....
Everyone (including Clive) is "over thinking" much of this...without actually doing much...

Originally Posted by tarian

Personally I think you are all over thinking the argument to eek out some more minimal power from batteries and thinking up large scale issues that are so far fetched its from Star Trek.

Originally Posted by tarian

to much over thinking for a battery system , this is not a nuclear plant

What is worse is that none seem to be grasping the fact that "thinking" is very good, but this "thinking" should be accomplishing an energy system design not speculating and trying to piece things together...

What I'm trying to say (again), is that Clive should design an on-board energy system for his boat, that meets his needs....and this must take into account all 3 of the main parts...energy storage (batteries); energy sources (solar); energy consumption (energy budget)....

12 pages, and other than my recommendation, still no mention of designing an energy system, nor even an idea of his energy budget?
This is what I mean by not accomplishing anything...

If he wants a 24vdc boat, that's fine...he can design a 24vdc system (and hopefully never need 12vdc for anything except an occasional device)...
But, why is everyone droning on and on about this or that device, and not asking about the energy system, nor even an energy budget??





2) Sorry about the confusion John61 and Noelex..I thought quoting the posting made it clear...

Originally Posted by john61ct

You're right, that would be stupid*, if that is how that type of converter works.

But, is that **really** how this type of converter works?

http://www.ykpowersupply.com/product_show.asp?id=4659

Vendor claims over 90% efficiency!

You weren't talking about solid state switching converters right?

But old-school linear voltage regulation.

I was responding to CatNewBee's comment regarding using a simple linear voltage regulator:

Originally Posted by CatNewBee

Not necessary to do DC-AC-DC conversion for step down from 24V DC to 12V DC. Just a regulator circuit needed - for small loads e.g. 7812 plus some capacitors.

As for the Yucoo's?
I have no knowledge / experience with them....but they are small switch-mode DC-AC-DC converters / inverters, so they may have RFI issues despite saying they have "EMI filters" and are CE certified....

FYI, generically, these days a "CE" certification is fairly meaningless (even COSPAS-SARSAT is working with the ITU and the EU, to try to get so many of these cheap Asian-based manufactured goods of all sorts to actually be tested, rather than just having a test report filed...but that's a whole 'nother discussion!)

So, be aware that you may find a nice RFI clean unit, and the next one (of the same model) might be truly crappy!
As we say: "ya pays ya money, and take ur chances"





3) Also, just a quick FYI for all...
When looing at anything electrical / electronics....if it has a "heat sink" and/or a "finned casing", and/or some other way of keeping it cool, please understand this means it needs this to dissipate the heat generated by its losses (inefficiencies).....but also remember that those without such heat sinks, etc. are usually just cheaper-designed units, where they don't care how hot it gets...

This doesn't mean that all of this discussion is moot....nope..
But, it does mean that when discussing "energy efficiency", it should be noted that many times what some think will save them energy, doesn't really save 'em much, if any...

Other examples are:
--- Autopilots....simply trimming your sails better will save you much more energy than trying to improve things by going from a 12vdc unit to a 24vdc drive unit....
--- Refrigeration / Freezer....simply adding adequate (more) insulation, which is very inexpensive and very easy for any layperson to do, will also do more than looking for minor energy savings in 24dc system..
--- Fans and lighting....of course good LED lighting and higher-efficiency fans (even at 12vdc) will also save energy...
--- Using some solar water heating (whether passive or active) will save a LOT of energy!! As will making sure that you do have a cooling loop from your main engine thru your domestic hot water heater, where even in 20 - 30 minutes of engine time can get you a fair amount of hot water, especially if supplemented with solar water heating...

Gosh there are lots of other ideas / ways of improving your energy system, saving energy, better energy storage, better energy charging, etc...
But, until we have an energy budget and an (preliminary) energy system design, much of what is being discussed here isn't actually helping much...






4) As I wrote earlier, and tarian eluded to, this isn't complicated...
So, Clive, perhaps take 5 minutes and try to forget all that you've read from those other websites (Aus outback exploration, off-grid homes, etc.), just for those 5 minutes....and then just reread what I wrote earlier....just 5 minutes of your time, without bias or preconceived supposition...and see what happens??
After those 5 minutes, if what I wrote regarding you needing to design an energy system (energy storage; energy sources; and especially an energy budget), seems like drivel, well then go ahead and continue on blindly and I will wish you well....but, maybe, just maybe, you'll see some light??

The reason I'm so insistent here isn't because of ego!
No...it is because of one or two small things you yourself wrote....it was when you wrote of having two 150 A/H batteries (giving you a 150 A/H @24vdc, house battery bank)....this just doesn't make any sense to anyone who is also looking for better energy efficiencies of large appliances, etc...

I am truly interested in helping you here, but I fear that my effort is fruitless...
So, Clive I really do hope this has helped you....but, if not, at least I tried...



Fair winds and good luck....

John

[noelex 77]

Originally Posted by ka4wja

Other examples are:
--- Autopilots....simply trimming your sails better will save you much more energy than trying to improve things by going from a 12vdc unit to a 24vdc drive unit....

Good comments, John. But there is nothing to stop an owner adopting all these measures.

For example, fitting a 24v battery bank does not diminish sail trimming skills.

At least not that I have noticed, although every time I pull on those confusing bits of rope the boat goes slower .

[ka4wja]

Noelex,
Of course, you're correct that better sail trim (or for that matter, better sails) and a 24vdc system are not exclusive...

As for pulling on those ropes and going slower...
We've all done that at some point.
Kinda like running aground...you know what they say, there are 2 types of sailors, those that have run aground and those that have lied about not running aground...

My late cousin Tom was an accomplished amateur Laser sailor back in the 1960's, winning some fair amount of races in Lake Michigan and Long island Sound, I think....and even he turned into a "if it ain't luffing, it's trimmed okay" type of sailor...



Fair winds..

John

[coopec43]

I bought a 17 lpm diaphragm pump for the water supply and was going to replace the 12V blower for the toilet/shower but maybe I should just try it on 24v?

Guyrj33 post #14 said "The fans, well I'd try them on 24v and see if they're ok. Most likely they'll just spin faster".
After seeing 12V/24V oscillating fans for sale on eBay for $26.95 I presume "they'll just spin faster" on 24V?

Maybe the 12V exhaust fan in the shower/toilet will just spin faster on 24V?


Clive