Cigarette Lighter Plug VS Direct connection to the battery, What is the difference?

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WarDemon666

Platinum Member
Nov 28, 2000
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I just bought a 120watt power adapter for my laptop, i plan on using it in the car and I want to mount it permanently in the car...

heres the product:

http://reviews.pricegrabber.co...es-adapters/m/8129785/

The problem is when it is plugged directly to the battery, the light powers on but my laptop shows that it is not plugged in.

Ive tried many solutions but the only way to get it working is to plug it into my cigarette lighter plug, and to start the car.

when the car is off (but ignition on) the light shows that it is receiving power but the laptop doesnt show as charging.

As soon as I start the car the laptop shows that it is charging, and when i turn the car off but leave ignition on, it still shows that it is charging until I remove the key..

This is the weirdest problem ive seen in years, I have no idea what could be causing this..

Any ideas what could be causing this problem?

Thanks everyone
 
Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
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The inverter is undersized and needs the additional voltage from the auto's charging system in order to put out sufficient AC voltage to the notebook adapter. Cheaper inverters do not put out true sinewave power and are frequently unregulated. The SMPS used by the notebook expects to see sine wave power between 90~250VAC - 50-60Hz typically. Stepped approximation to sinewave power will require higher peak values to satisfy the input requirements of the SMPS.

Solution? Purchase a larger inverter or a true sine wave regulated inverter. The latter is much more expensive but your SMPS in the adapter will perform as designed.
 
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WarDemon666

Platinum Member
Nov 28, 2000
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Originally posted by: Rubycon
The inverter is undersized and needs the additional voltage from the auto's charging system in order to put out sufficient AC voltage to the notebook adapter. Cheaper inverters do not put out true sinewave power and are frequently unregulated. The SMPS used by the notebook expects to see sine wave power between 90~250VAC - 50-60Hz typically. Stepped approximation to sinewave power will require higher peak values to satisfy the input requirements of the SMPS.

Solution? Purchase a larger inverter or a true sine wave regulated inverter. The latter is much more expensive but your SMPS in the adapter will perform as designed.
Click to expand...

I am not using an inverter!

It is a 120watt power adapter that you plug either into a 120v adapter, or a lighter plug, and its supposed to power your device.

The wires I used to connect the adapter to the battery were connected directly to the battery (2awg too!) so it was getting the maximum power possible. Could it possibly be getting too much power?


From what I know the lighter plug will have a greater resistance than the direct cable and will allow for much less power than if connected directly..

I'm really confused as to why it only works with the lighter plug,,, if its connected directly to the battery it does not work.... Very weird.

If anyone has any ideas please don't hesitate to post, im confused!

Thanks & take care
 
LTC8K6

LTC8K6

Lifer
Mar 10, 2004
28,520
1,575
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Sounds like it doesn't work unless the voltage is high enough. Starting the car brings the voltage up and charges the battery, so it turns on and stays on when you turn off the key.

Maybe your battery is a little dodgy and the voltage drops too low unless the car is running?

That wouldn't explain the direct connection problem though.

Maybe check your battery voltage with the engine off and the headlights on?
 
Rubycon

Rubycon

Madame President
Aug 10, 2005
17,768
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Originally posted by: WarDemon666

I am not using an inverter!

It is a 120watt power adapter that you plug either into a 120v adapter, or a lighter plug, and its supposed to power your device.

The wires I used to connect the adapter to the battery were connected directly to the battery (2awg too!) so it was getting the maximum power possible. Could it possibly be getting too much power?


From what I know the lighter plug will have a greater resistance than the direct cable and will allow for much less power than if connected directly..

I'm really confused as to why it only works with the lighter plug,,, if its connected directly to the battery it does not work.... Very weird.

If anyone has any ideas please don't hesitate to post, im confused!

Thanks & take care
Click to expand...

Ok forget the inverter part. But most likely it still has an inverter - DC to DC type as many devices - particularly portable PC's - require more than 12VDC.

If it's a straight tracking DC-DC inverter then your input voltage dipping will directly affect your output voltage. For the most reliable operation in a vehicle it's best to use an inverter that will produce power for the original manufacturer's power supply to avoid these issues.

 
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WarDemon666

Platinum Member
Nov 28, 2000
2,224
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maybe its just a defective unit? I'll try checking the voltages from the cig. lighter vs direct connection, but, i dont understand!! could there be some kind of component that 'detects' the resistance of the connection making sure its connected to the cig. lighter and not a direct connection? (its a long shot but it may be possible??)

Thanks all
 
J

jsbush

Diamond Member
Nov 13, 2000
3,871
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Originally posted by: WarDemon666
maybe its just a defective unit? I'll try checking the voltages from the cig. lighter vs direct connection, but, i dont understand!! could there be some kind of component that 'detects' the resistance of the connection making sure its connected to the cig. lighter and not a direct connection? (its a long shot but it may be possible??)

Thanks all
Click to expand...


It's very simple. The device needs more then the regular 12volts from a car battery to power on. When you start your car, your alternator probably puts out somewhere along the lines for 14.4volts.

Once the adapter is powered on, it sounds like the voltage from the battery is able to keep it alive, since the device is already on.

Most eletrical devices require more power at start up, then actual running power. You should know that :p. lol.







 
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