Laptop in Car: Tips & Tricks

edit: split from https://community.dieselschrauber.org/en/viewtopic.php?t=4590
gremlin


Hi,

Gremlin is absolutely right. The IBM device requires 16.8 volts, so a simple charging cable won't do the job.

There is a car power adapter for it, but it costs over 200 euros.

Since I received the 12->230V inverter as a gift, that's the much simpler solution. However, I don't understand why VAG-COM no longer works, because I'm quite sure that the inverter provides galvanic isolation, and I know that's the case with the laptop power supply.

Einziger Grund kann sein, dass der Schutzleiter des Netzteils (dieses Notebook hat ein Netzteil mit dreipoligem Stecker) beim Betrieb am Inverter nicht "geerdet" ist, wobei ich auch da keinen wirklichen Zusammenhang sehe. You?


Jan.

Einziger Grund kann sein, dass der Schutzleiter des Netzteils (dieses Notebook hat ein Netzteil mit dreipoligem Stecker) beim Betrieb am Inverter nicht 'geerdet' ist, wobei ich auch da keinen wirklichen Zusammenhang sehe. You?
Jan

yepp...

It is called mass entanglement and scattering.

You now have two switching power supplies in series. On one hand, you have the DC/AC converter, and then the laptop power supply, which is an AC/DC converter. http://www.handykult.de/plaudersmilies.de/party/ylsuper.gif

Switching power supplies always leak somewhere. If your laptop power adapter even has a ground connection, that's a good sign of this kind of issue.

Normally, the ground and the enclosure are connected via capacitors, which allows high-frequency interference to flow to ground. However, this is no longer working.
It's quite possible that they could fail between the converters.

DC/AC converters are designed for resistive and inductive loads. However, a switching power supply represents a capacitive load. Consequently, most simple DC/AC converters will start to oscillate uncontrollably. My old 500VA UPS does this (when only the computer is connected) in approximately 2 seconds. Then, the power outlet switch starts flickering as if it were possessed.
Try connecting a larger AC/DC power supply with a transformer.

Furthermore, your laptop is completely potential-free compared to a car... or is it?
It depends on the adapters being used.
In this case, you shouldn't encounter any problems (aside from the ones mentioned above). However, some of the adapters have a connection through ground. While these adapters always include 100 ohms, that might still be enough to cause interference. Just for fun, try using a high-impedance voltmeter and connect it to the vehicle's ground and pin 5 of the COM port. You might see anything from 0 to over 100 volts.

Okay, and also, try connecting the ground pin of the laptop power adapter to the vehicle's chassis ground.

CU Gremlin.

Hi,

'Inverters can be a significant source of interference; it's difficult to make phone calls or listen to the radio near a cheap inverter. Since VAGCOM interfaces are already quite sensitive and their performance can fluctuate, I would consider this as a possible cause.'

If your interface provides galvanic isolation (AND ONLY THEN!), then buy three single-cell batteries for testing (alkaline batteries typically have around 16Ah).

Connect them in series and to the car's 12-volt power supply, then connect that to the laptop. It should then charge and work. (12/13.8 V & 4.5 V = 15-18 Volts)


Since the monochrome printers are not very expensive at stores like Aldi, Lidl, and Penny, they could be a solution if you don't need to print very often.

Sure, I'll let you know when it's done.

Hello everyone,

Let's see if this works; I'm sending this via mobile. I'm accessing dieselschrauber.de and using Wi-Fi from my Sharp Zaurus while I'm sitting in a presentation...

Regarding the battery solution: It seems too risky to me, because the voltage is not stable (13.8...14.4), and it's also not really regulated. Furthermore, and this is the crucial point, my adapter is not galvanically isolated.

The issue with the interference caused by the inverter makes sense to me, although it seems to be an electrical problem, since the computer is still running.

It seems like Gremlin's idea of connecting the power supply's ground wire to ground is a good one. The only question is whether the ground wire is connected to the secondary side (which I need to check), because otherwise, there would be problems with the adapter.

Do you foresee any other dangers if the cable isn't routed through the power supply?

Best regards,

Jan.

Connecting the ground wire of the power supply to ground seems like a good idea. The only question is whether the ground wire is connected to the secondary side (which I need to check), because otherwise there would be problems with the adapter.

Do you foresee any other dangers if the cable isn't routed through the power supply?


Okay... I have Jeff's interface, which provides galvanic isolation, but the laptop is connected directly to the ship's power supply via a cigarette lighter adapter. So, there's no potential separation.
The protective conductor is definitely not connected as a secondary ground. That would be quite extreme...


CU Gremlin.

edit: split from https://community.dieselschrauber.org/en/viewtopic.php?t=4590
gremlin


Hi,

Gremlin is absolutely right. The IBM device requires 16.8 volts, so a simple charging cable won't do the job.

There is still a car power adapter for it, but it costs over 200 euros.


Jan

Hi,

Take a look at www.reichelt.de. They have universal switching power supplies for laptops with 70 watts and an 11-14 volt input. The output voltage can be adjusted between 15 and 24 volts. This should be ideal for the purpose and costs only 34.70 EUR.

Greetings.

Eike.

Hi,

@Eike: That should also work, and you're right.

@Gremlin: I'll try testing the grounding next, maybe that will be enough. It's not so bad that it doesn't work at all, it's just that the connection breaks very quickly when the engine is running.

Best regards,

Jan.

Try putting an isolation transformer between the laptop and the inverter.
I think it will work, but I'm not sure. Maybe you could try it and post the results.


Regards,
Bubu.

eike wrote:

Take a look at www.reichelt.de. They have universal switching power supplies for notebooks with 70 watts and an 11-14 volt input. The output voltage can be adjusted between 15 and 24 volts. This should be ideal for that purpose and only costs 34.70 EUR.

"I use a part exactly like this for my IBM laptop, and it works perfectly. I paid 25 euros for it at the online retailer E-..Y."

I also have the one from reichelt.de, but I didn't buy it from e---y (I should have checked!). It works perfectly on my old, somewhat demanding, and generic laptop. You can buy it and don't have to do any modifications.

Hi,

Do these devices have galvanic isolation between the primary and secondary sides? My car adapter doesn't have optocouplers, so this could be a problem.

Best regards,

Jan.

Hi,

Do these things have galvanic isolation between the primary and secondary sides?
Not necessarily. A small voltage increase can be achieved using choke coils.

btw: I can't find the power supply listed above on the Reichelt website... either I'm too stupid to search, or the wonderfully certified company Reichelt doesn't want to sell it to me.
I'm already over them. They're riding on their high horse and packaging semiconductors as bulk material in plastic bags!

CU Gremlin.

Jan6K wrote:

...do these things have galvanic isolation between the primary and secondary sides?

Mine would, because I would consider 4.9 MΩ to be a level of galvanic isolation.
This device still draws 2.9A even at 24V!

http://www.vanson.com.hk/details/vansonnel2024a.html

http://www.vanson.com.hk/cgi-bin/ngen_details.pl?UCODE=238971&LANG=&LOOP=PROD

Hi Bertil,

That sounds very good! I need to check if I should buy something like this instead of trying to use mass cables, because the prices sound absolutely reasonable, and it would save me from having to carry around another device.

Best regards,

Jan.

Hi Jan,

The fluctuating voltage isn't a problem as long as you stay within certain limits, because there's another (step-down) switching regulator located at the power input of the laptop. It can certainly handle up to 19 volts; how low you can go would need to be tested. You could also use one more cell and stabilize it at 16.8 volts with a low-dropout regulator, but I don't think it's necessary.

Since you're not using galvanic isolation, that will only help you charge the battery.

'Using an isolation transformer is not a good idea because the (cheap) inverter essentially produces a square wave voltage, and transformers react to this due to the extremely high harmonic content, generating a lot of heat. Furthermore, the transformer is very inductive when idle, which can damage the inverter. This doesn't apply to pure sine wave inverters, but they also don't have the interference problem.'

Hi,

and that's exactly why it's very ineffective. Because it's usually full after about an hour, and then it only lasts for 5 minutes .

Therefore, I will first test the variants that use galvanic isolation.

Best regards,

Jan.