19 vdc powersupply question

Gunner Asch fired this volley in news: snipped-for-privacy@4ax.com:

The most intuitive solution is to buy a small inverter, and run the laptop off 120VAC.

Lloyd

I'm not sure the eBay DC/DC converters would handle 90W.

Lloyd's suggestion of an inverter sounds reasonable. You probably already have one. They go on sale at HFT for $20ish often, if not. The 200w models 61478 and 66967 are on sale for $23 now, and 400w models are $26. They've gone up.

Hey, Mr. Electrician/Electronic tech, way to show your ability!

LOL Ok, this being such a complicated problem, how about 12V -> inverter-> wireless cell phone charger -> 4X magnifying glass -> laptop.

Get an inverter and connect it up. Ran one for years in the van. Also handy to run a small microwave or ???

This also gives the benefit of filtering the power much better than a direct converter.

In my experience they generally RUN fine on the 13.75 +/= volts, but don't charge the battery.

autmotive laptop charger, like this, but check connector sizes first

I made up an adapter cable that fed 14.x V straight from the car's electrical system to the 19 V input of a Dell. It actually worked, but I got nasty messages about a low battery.

I eventually bought one of the eBay 19 V converters, and it works great.

Jon

Hmm ... that it 4.74 Amps at your 19 V. I would aim for 5V as a minimum, just to handle starting surges.

6.55 A from your 13.75 Volts from the car, assuming 100% efficiency, which you won't get.

You *could* use one of the inverters to go to 120 VAC, and then plug the power supply which belongs to the laptop into that. But that is electrically inefficient. And -- make *sure* that the output waveform is clean enough so the laptop's power supply won't barf.

Looking through Mouser's DC-DC power supplies, I find it difficult to match what you need there, so you may be stuck with the kluge.

Now, this looks intersting on eBay (281797179064), though I would like to be able to download a data-sheet/manual to read about it in detail. However, it appears to accept any input voltage from 10V to

60V so it would cover your 13.75, plus the variations when the car is running or stopped), and output from 12V to 60V. I see two pots on it, one for adjusting the output voltage, and the other for adjusting a current limit on the output.

It is $13.84 (plus possible import fees). :-)

My thoughts, and a quick look at eBay to see what you are talking about.

Good Luck, DoN.

The reason you want to keep the unit using it's own supply is reliability.

It was designed for 120v and it is designed to power the pc.

Supply the 120v and the pc will see the same signal. Maintain itself. Just have a sine wave 120v so harmonics are not generated that might do bad in a supply expecting a wall plug 120v 60Hz supply.

Martin

Unless I missed something, this thread is about laptops, which are designed for ~20V DC input. You can get that from AC or DC adaptors approved for the job.

I've had a good laugh reading this thread. The average 12 year old needing a vehicle power supply for a laptop would probably google "car laptop adaptor" and within an hour order one of a zillion available adaptors for peanuts. But master electrician/electronics tech Wieber plots yet another longest road to a corrupt solution. Soon he'll be asking what size wire to use for his new inverter, and why his van won't start after he cooked some road kill for a half hour in his microwave.

SMPS units are pretty tolerant of dirty power and virtually all laptop power bricks are SMPS.

iI don't think you understand Martin, it is a LAPT OP and it runs on DC. The AC ppower supply converts anything from 80 to 240 volts, 50 to 60 hz to DC to run the laptop

Get a life.

I know what I'm taking about - you don't.

I know the PC is a box. I know a supply powers the box. The supply is trying to be replaced.

I say keep the supply as the impedance.... matches the box. Simply have a supply that provides the input power of the supply.

e.g. 12V to 120 to 120 to 19v to box. The 12VDC (boat/car/truck) delivers 120 V AC to the standard power supply that came with the PC and that power supply powers the PC.

It makes a 12V to 19V supply with a 120vAC cable between...

Mart> >

Works fine, as long as you have an essentially unlimited supply of electricity from the alternator on the running engine to cover the losses in kicking the power up from 12VDC to 120VAC, then the additional losses of going back down from 120VAC to 19VDC.

Unless you have other gear that also can use the 120VAC from the same inverter, it's rather silly to convert it twice...

Now the kicker - If you are running off a battery or a current-restricted power port, all of a sudden going straight from

12VDC to 19VDC at very low overall conversion loss starts looking a whole lot better.

What pisses me off is that 19V changes with every generation of computers, next year it will be 17V or 21V and a slightly different connector, like the new Triaxial ones with a third communications pin to allow battery charging control on Laptops - just so they can sell you a new converter every time.

I have a stack of obsolete Auto-Air-Travel100-120-240 converters that promised interchangeable connectors and variable voltage output so it would be forward adaptable forever. And all of them were thwarted by the Laptop industry making bigger changes than the vendors could accommodate, like that third pin comm-port.

-->--

Since virtually all laptops today run on 10.7 volt batteries, they run just fine on a "12 volt" power outlet but the batteries won't charge fully (if at all)

The upconverter listed by someone earlier from e-bay works well for the currents involved to make charging the battery possible.

All the cheapies are modified sine wave and I've heard that power tool battery chargers don't like them much. I haven't tried my chargers on either the old 400w or new 2000w HF inverters yet. The only test I gave the big inverter was to see if it would power the chainsaw so I could cut wood when the grid goes t*ts-up, and it did. I may need a better inverter to power my furnace, too.

Being a big buyer of cheap Chinese gizmos, all I can say is: If it needs 100w to run, buy at least a 300w converter, if not 400. They are very competitive and not very honest with their figures. Kinda like Searz horsepower, y'know? None of the vendors know -anything- about power or tech specs, so if you ask them a question, make sure they ask their engineer for the actual answer. Figure a week for a reply in most cases.

I can check tonight, but my guess is it has no name or other ID on the thing. I bought it at least a year ago, and have used it on a Dell laptop. I use that as a great big GPS when traveling, so the computer can stay on for quite a few hours off the car's power.

I got the adapter off eBay, I'm pretty sure.

Jon

If you check your old email from eBay, you should see the model number or listing title. Either usually works.