Running a lap top efficiently?

Originally Posted by whoosh

thats what I said CDK, twice as many amps 110 as 230

Well, that was definetively NOT what you said..............quite the contrary..

........but who cares.

Cornelis

especially in Germany I cannot imagine how burdensome it would be to avoid the Autobahn.

Being a biker I always choose the more enjoyable Landstraße, but for a trip of the length you made? No, there will be at least half the way on the "Gas, Gas Gas auf der Autobahn"

Regards
Richard

[DennisRB]

Cheers. Yeah something must be wrong in that inverter. Thing is it also struggles on a 300W inverter I tried with several laptops. I guess that this could be because the inverters are both pretty old and cant handle electronic switching circuits as loads. The sharp shapes of the power curve of the electronic power supply might cause a few probs. I am going to measure the current draw on the 240v side at home to see if there is any difference when its plugged in the inverter. That link on power usage was great too, thanks.

[DennisRB]

I am trying the 300w inverter. Its square wave. This is the first time I have used my new laptop on this inverter.

I have actually measured current draw from the 12V battery supplying the inverter this time.

With no laptop battery it draws on average about 3A or 35W from the house battery. Thats a small load!

However when I plug the lap top battery in (its 96% charged) its using 5A and this is enough to trouble the inverter. Any current spikes over 6A will bring the overload buzzer on the inverter on. I have seen 8A and it would have shut off it had not only been for a second. Once the battery was 100% charged it didn't seem to draw anymore than with no battery in. I expect that with a 100% flat battery the current would go off the scale. That is probably why the laptop power supply is rated for many more watts than the laptop and I expect charging it would overload many small inverters.

So the question is why does a 300W or 500W inverter start crying enough when clearly there is never more than 100W going through it? I wrongly assumed the inverters were actually overloading because the loads were high, but they are not.

I guess its because the inverters are old square wave? Or just crap? And cant really handle switch mode power supplies?

[CDK]

If the inverter draws 3A at idle, throw it in the dumpster. It should be around 1/10 of that.
With long or too light 12 V leads, the inverter complains about the input voltage, not about the load.

For any inverter a switch mode supply is just a rectifier and a capacitor: it cannot "see" beyond that, so that is not the cause of your problem.

[DennisRB]

3A is running a laptop with no battery installed. The inverter was hooked straight to the battery terminals with short leads.

[TerryKing]

Originally Posted by DennisRB

3A is running a laptop with no battery installed. The inverter was hooked straight to the battery terminals with short leads.

Dennis, maybe the variable is not the Laptop (Runs at low power with the 12V - Laptop charger).

Maybe it's the original AC Mains to Laptop Charger you have. That's the common factor connected to the inverters that seems to draw excessive power. Maybe it's Power Factor (Peak VS Average power per cycle) is poor (some of these are notoriously bad)..

The Ebay type charger is apparently a modern design switching power supply and does the voltage conversion in one step, so higher efficiency.

The only concern I would have is possible problems from the voltage surge that happens when an engine starter motor is cycled to start the main engine. Early versions of 12V laptop chargers had problems with this. I would consider putting some bypass capacitor(s) and possibly a 20 V or so Zener diode surge suppressor at the 12v connection to that Ebay charger. Just for insurance..

The Car-Computer and 500W Car-Stereo guys have been thru all this. Take a look at http://www.mp3car.com/ and follow some of those links.

And have fun on the water!

[DennisRB]

Thanks for the tips. I have tried both inverters with different laptops with the same probs.

I just got my DC/DC unit and out of all the connectors that came with it none fit! Where am I going to get the right plug for this thing?

[DennisRB]

I just got my DC/DC unit and out of all the connectors that came with it none fit! Where am I going to get the right plug for this thing?

[CDK]

Dennis, the answer is in post #11.

[DennisRB]

I really don't want to damage my original power supply given I will be using it more often that the DC/DC converter. I could solder an adapter plug to the original power supply lead so I can swap it over. But my laptop is fairly new and still under warranty.

I would love to find a plug. But I guess this can be very difficult? Its samsung laptop if this helps.