24 Volt DC to 12 Volt DC Converter Question

[scootertrs]

Hello:
I have 24V to 12V converters that put out 13.5 amps continuously. I would like to know if these converters can be run in parallel to increase the output capacity. Maybe 2 or 3 of the units side by side powering a high amp draw such as a light bar or maybe even an electrical winch. I have done "some" testing with OK results, but I sure as Heck do not want to recommend someone to do this and have it do a smoke test or worse. Anybody else try this? The converters I posted have the following terminals: +24, common -, +12 . My plan was to hook up the +24's together, then the Commons together and finally the +12's together, hopefully multiplying the +12 amperage by doing so. Any ideas?

I have also considered adding a 12Volt battery as a power source and use the 24V-12V converter as a battery charger/maintainer.

Thank you for the help

 

[cranetruck]

In parallel, the power supplies may not respond at the same time to changing load conditions and will overload (burn out) one at a time unless designed to operate in this manner.

Using another power supply for a battery maintainer is normal (120VAC power), but with another lead-acid battery in the circuit, it will also need a maintainer.

A good battery maintainer restores charge to the batteries also and it may represent quite a load on the new battery in the circuit.

 

[Carl_in_NH]

Concur with cranetruck - most DC-DC converters were not designed to load share - and won't work properly in parallel. Converters that are designed to do so will advertise that fact, and must only be parallel with another such converter that can load share.

Buy a bigger one to power your loads - or another small one, and split your 12V loads between them.

Electric winch on a DC-DC converter? No, don't even think about it. Most converters are designed to protect themselves against an output short circuit and will "fold back" the output voltage in that event. A DC motor undel heavy load looks more and more like a short as the load increases to the converter - so when you load the winch with weight the converter will start limiting the output and make the winch stop pulling.

If you must have an electric winch, get a 24V one and be done with it. Smaller copper to run to the battery, too.

Keep the DC-DC converters for radios and such and you'll be a happy camper. 12V lights? Re-wire them for 24V by disconnecting the ground internal in the light housing and running the wire out so you can connect two of the same type light in series and run them off 24V.

 

[mikew]

These DC-DC converters will load share:

NEW Vicor VI-200 Module Vi-211-EU DC-DC Converter - eBay (item 360097433333 end time Oct-07-09 17:22:28 PDT)

They are actually converters for computer equipment. They are 200W, so about 15 amp each. And, completely waterproof.

And this guy is selling them WAY cheap, I just bought 11 of them for less than $100.

Mike W

 

[cranetruck]

Mike, you may want to check the specifications to make sure they can handle the automotive electrical environment. Some input protection may be required and, at least, wire them so they are not on when the engine is started.

 

[mikew]

I will also add that I will be using 3 or 4 of those DC-DC converters in parallel as a battery charger. The output voltage on these converters is adjustable and you can use a battery charger "chip" to control that voltage for use as a multi-stage charger. Vicor, the converter's manufacturer, has a technical document with schematic that shows how to do it.

I need new batteries in my bobbed deuce, so I'm going to buy three group 31 batteries. They should all fit in the battery box. Two of them will be hooked up normally, the third battery will be charged by the converters when the deuce is running.

I will be using the third battery as a power source for a rear mounted 12v winch, not to mention other 12v accessories.

I know, why not just buy a 24v winch... they are too darned expensive! I just need a winch for stuff like pulling a car onto a trailer pulled behind the deuce, not recovering a tank stuck in the mud, so a $300 "chinese" winch will do.

Mike W

 

[mikew]

The modules in the link above are 21v to 36v input (they also make a 10v to 36v input version) and shutdown if the voltage goes too low.

And yes, an inductor with a capacitor (basic low pass noise filter), not to mention a fuse, will be on the input side.

Mike W

 

[scootertrs]

INteresting... I specially like the "waterproof" part. I am concerned about heat dissipation in their web page Vicor displays heat sinks and fins... I also could not see anything about load sharing... Mike I would like to see a basic diagram of what you have in mind... my electronics knowledge is based around 6L6 and 12AX7 tubes ... any help would be greatly appreciated, specially in your design of the circuitry that will be charging the battery. BTW, I agree that with the limited use I will be giving my rear winch, I see no need to go the pricey 24V route if I can get away with a basic 12V model... since I am going to need my 12V for my beacon lights and strobes... (fire truck -you know... gotta have them)

 

[Carl_in_NH]

my electronics knowledge is based around 6L6 and 12AX7 tubes

Then we must chat sometime, as I'm a lover of hollow-state electrical devices as well. Radios that glow in the dark are a source of true enjoyment. Military tube radios? Even better.

I'd also like more information on your fire truck. Is that a 530? Have you seen the cover of the latest issue of Supply Line?

 

[shootiniron]

Stupid question from the electronicaly challenged.Can you use the above mentioned converters for say,cell chargers etc. and how would you wire it in?

 

[cranetruck]

Carl, if you know what a "filament transformer" is, then you are probably in my age group.
...I'm not much for chatting, though.

 

[Carl_in_NH]

Indeed I do know, Bjorn. I come from an interesting time - when both tubes and transistors saw service at the same time.

 

[mikew]

OK: Power Sharing, figure 2 on page 2 shows how to connect the converters from the previous e-bay link. Easy.

http://cdn.vicorpower.com/documents/industry_articles/ia_1999_pwrarrays.pdf

These two articles show how to do a multi level charger, but not for non-electronic type folks:

http://cdn.vicorpower.com/documents/application_notes/an_ConstantCurrent.pdf
http://cdn.vicorpower.com/documents/design_articles/pb_battery-charger.pdf

Setting the output on the converter to 14.1 volts would approximate how a generator charges, adding a thermistor for temperature compensation would be even better. Once again, stuff for electronic type folks!

The converters have a flat aluminum plate for mounting. Bolting that to a piece of sheet metal would be a fine heat sink unless you are looking to pull maximum power most of the time, then a finned heat sink would be a good choice.

Cell phone charging: You could use one of these converters to supply 12v to an accessory outlet (cigarette lighter outlet) and lust plug in a car charger for your favorite electronic device.

Mike W

 

[scootertrs]

Hi Mike and thank you for your help and patience. I have downloaded their manuals and specs but I cannot see if the neg of the input can be physically linked to the negative of the output. Since most of the items I want to power 12 v or 24 share the ground, I don't know if the Vitors allow it. They are definitely a great deal if we can get them to work. Also, I have not cleared up the question of heat dissipation.

 

[mikew]

I'm using one in my deuce to power a radio, and yes common ground.

Mike W

 

[fireman9]

Hi Mike and thank you for your help and patience. I have downloaded their manuals and specs but I cannot see if the neg of the input can be physically linked to the negative of the output. Since most of the items I want to power 12 v or 24 share the ground, I don't know if the Vitors allow it. They are definitely a great deal if we can get them to work. Also, I have not cleared up the question of heat dissipation.

I'm going to go the easy route and add a GM one wire 12 volt altenator and additional 12 volt battery, run everything thru a constant duty solenoid and wire that off the main switch. Same thing here tow-way radio, light bar, scanner, steamlight charger, portable radio charger, etc. ( I do HAVE a 24v federal "Q" too)
I was looking at the voltage converters but there to rich for my taste and limited output just don't add up with the seprate systems battery maintainers are easy to install too.

 

[Engine5]

Scootertrs,
Not to change the subject, but did you see the cover of "Supply Line" magazine? I think you will like it.