Inverter problem

Most inverters don't produce a true sine wave. While this doesn't matter much for most mains loads it may well for a switch mode power supply.

"Golf" schreef in bericht news: snipped-for-privacy@d55g2000hsg.googlegroups.com...

What happens if you connect other loads like lightbulbs? When 100W or even

Unless you have a high quality (and expensive) inverter, it will not produce sinewaves but so called modified sinewaves. The shape of the load performed by the laptops powersupply may cause the problem in this case. Try a choke between the inverter and the power supply to smooth that modified sinewaves. I suppose a 1H/1A/60Hz type will do. The choke should not go into saturation as it may make things worse.

petrus bitbyter

I have a 400 watt inverter (peak 800). I have an old PII laptop with no battery. In the interest of science, I hooked them up. No problems. The laptop power supply says DC Output 19V 2.6A.

Forgot to add that I am in the US. That I don't use the cigarette lighter, just a direct to the battery connection using cables. If overloaded, my inverter doesn't say much. It just shuts down, but if the connection is hot, that indicates something is overloaded.

What kind of power does the hole in the back of the laptop want? I'll bet good money it's a DC voltage with relatively low current. What I'm getting at is that rather than convering DC to AC and back to DC to use your existing AC adaptor, you'd be better off using a true DC-DC converter... I think my Toshiba runs at about 15VDC, so you'd need to actually increase the voltage which rules out most Radio Shack cig lighter power adaptors.

You could build something cheap using a 12V regulator and a couple of diodes to bring up the voltage, or buy one of the many commercially available dc-dc converters. I've seen them as cheap as about $10 as surplus, you'll have to poke around a bit to find one with the right specs.

Or, as another poster has suggested, try placing a 1H choke on the output of the inverter to smooth out the power a bit. If the inverter is squealing, it's working very hard and soon the magic smoke will escape.

Dave

If the cigarette lighter plug is becoming too hot to handle it sounds like the socket could be dodgy and therefore may be incapable of supplying sufficient current to the inverter, is there any way you can try connecting the inverter with a pair of croc clips directly to the battery?

Also although the output from the inverter may not be a true sine wave it will usually be fed straight into a bridge rectifier and reservoir capacitor arrangement and then as circa 320V DC onto the switch mode power supply circuit, so will probably not be that critical anyway.

A better solution for powering a laptop is a mobile DC power supply, which is a DC-DC converter with 12 volts in and your choise of volts out (typically 15-19).

It's more efficient than the DC-AC inverter > AC-DC power supply combination and draws less current than the DC-AC inverter does.

It's also a lot cheaper, starting under $20US:

John

How heavy are the wires? The wattage on the input will be a bit more than the wattage drawn from the output, but given the voltage is lower by a factor of 10, the current draw will be 10X what it would be at 120V so you need some pretty heavy wiring for anything over a few tens of watts.

Most inverters come with a fitted lead and plug to fit the cigar lighter - and one for clipping direct to the battery if they can exceed the 10 amps or so allowed by most cigar lighter sockets. So saying not all cigar lighter sockets are identical and mate well with these plugs at higher current.

I'm actually surprised a new standard for a car power take off hasn't evolved given just how unsuitable the cigar lighter idea is since it uses steel contacts.

The leads are about 2 feet long and are made from 12 gauge wire. They came with the unit. I didn't think the cigarette lighter business was a very good idea, so I've never used it.

Golf you have a real curiousity there. I have been doing this for years.

Just some questions\\

Does your HP work fine when it is plugged into a normal socket? Can your inverter power a 100 watt light bulb? Is your PS cable unmodified and in good shape

If all above is OK then your problem must be "fm.".

yours jim

The answer is yes, yes, and yes. I have since found a DC/DC converter made for auto cig lighter plug made by HP. It is about $75.00. Had found another brand that had higher power limits for about $100.00, but figured the HP would be fine. I should state that I listed all this info on behalf of a friend. I probably would have looked for a DC/ DC converter before I bought an inverter soley to run my laptop in my auto. Kinda strange going DC/AC/DC. Thanks for the reply.