how many volts is too many ?

Submitted: Tuesday, Aug 21, 2012 at 10:01
ThreadID: 97551 Views:2301 Replies:6 FollowUps:7
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I bought a 12v car charger the other day and after using it for a couple of hours the laptop gave up the ghost turns out the main board is fried.
The laptop has a nominal input of 12 volts and when I check the output of my ac adapter it has an out put of 12.25 volts. On checking the output of this new unit it has an out put of 13.7 volts even though it says it is 12v.

So my question is ...........is the 13.7v enough to damage the laptop ie fry the main board?

cheers
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Reply By: Member Andys Adventures - Tuesday, Aug 21, 2012 at 10:21

Tuesday, Aug 21, 2012 at 10:21
Most laptops are 19v. Are you shore the laptop is only 12v
AnswerID: 493312

Follow Up By: Member - wicket - Tuesday, Aug 21, 2012 at 10:30

Tuesday, Aug 21, 2012 at 10:30
Definitely sure, is an eee pc and input is clearly shown on specs.
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Reply By: TerraFirma - Tuesday, Aug 21, 2012 at 10:32

Tuesday, Aug 21, 2012 at 10:32
Not sure what you mean by new unit? The 13.7 volts is common, the voltage is stepped down by internal rectifiers and regulators etc. Laptop motherboards fail every now and then just like a normal PC mainboard. What brand laptop is it? My recommendations when buying laptops is stick to brand names, stay clear of no-name stuff due to quality and inability to buy parts. So no is the answer.
AnswerID: 493315

Follow Up By: Witi Repartee - Tuesday, Aug 21, 2012 at 10:56

Tuesday, Aug 21, 2012 at 10:56
I think ASUS qualifies as a well known brand. Also many motherboards and components in other brands of computers are manufactured by ASUS. While I have not owned an EEEE ...we have caravanned extensively around Australia with his and hers ASUS laptops and had no problems.
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Follow Up By: TerraFirma - Tuesday, Aug 21, 2012 at 11:22

Tuesday, Aug 21, 2012 at 11:22
yes agreed, big fan of Asus products.
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Follow Up By: get outmore - Tuesday, Aug 21, 2012 at 21:12

Tuesday, Aug 21, 2012 at 21:12
last I checked asus were very much at the cheaper end of laptops - not saying thats the issue, ive always run laptops off of 240v inverters with no issues
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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Aug 21, 2012 at 21:21

Tuesday, Aug 21, 2012 at 21:21
After ruining a mobile phone with a 'cheap' car charger I have since been careful to only use car chargers supplied by the appliance manufacturer or use the supplied 230v charger from my pure sine wave inverter. Also 'no issues'.

Cheers
Allan

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Reply By: Andrew - Tuesday, Aug 21, 2012 at 12:28

Tuesday, Aug 21, 2012 at 12:28
Hi Wicket

Supplying a voltage higher than the system is rated to receive can definitely do damage. Depending on how the laptop is set up internally it could have cooked a battery or blown the internal power circuitry, both of which I have seen before. Seems strange to do the motherboard as I thought the other things would get in the way first, however have no specific knowledge of your product and some of the tech experts on site might have a better idea.

It is also worth checking that the charger is actually limited to 13.7 as if that's only averaged you may be seeing peaks much higher than that.

I would assume that the original unit output is pretty well controlled and matched to the laptop.

regards

A
AnswerID: 493324

Reply By: Honky - Tuesday, Aug 21, 2012 at 15:46

Tuesday, Aug 21, 2012 at 15:46
I am sure i have read that even to little voltage will damage a computer.
If it is meant to take 19 and you supply say 14 volts it can do damage.
Someone else may be able to confirm or denie this.

Honky
AnswerID: 493341

Follow Up By: olcoolone - Tuesday, Aug 21, 2012 at 17:42

Tuesday, Aug 21, 2012 at 17:42
I'm sure you meant the other way around.... the laptop requires a 14v input but you ran it on 19v.

If it was the you said the laptop would not power up.
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Follow Up By: Allan B (Member, SunCoast) - Tuesday, Aug 21, 2012 at 21:04

Tuesday, Aug 21, 2012 at 21:04
Honky, I read your expression as questioning the risk of supplying under voltage (too little).

I would expect that a computer requiring 19v would not run on 14v but I have never seen damage caused by under voltage.

Cheers
Allan

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Reply By: Allan B (Member, SunCoast) - Tuesday, Aug 21, 2012 at 21:15

Tuesday, Aug 21, 2012 at 21:15
Hi Wicket,

If you measured the new charger without the computer connected (no load) then I would expect that its output could be 13.7 volts, or even more. This would drop to around 12 volts when loaded. So there may be no voltage problem with the new charger.

There could be other than voltage problems with it however. It may have a high 'ripple' in the DC output or it may be producing spikes. This is especially so if it is a cheaply-priced unit.

Whoever told you that the "main board" is fried should be capable of testing the car charger and advising if it is suitable or not.

Cheers
Allan

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AnswerID: 493361

Reply By: Member - wicket - Wednesday, Aug 22, 2012 at 10:16

Wednesday, Aug 22, 2012 at 10:16
I rang my local laptop repairer and he felt that new car charger at 13.7v would be ok and probably did not cause the damage , the fact that it happened the first time I used it was more than likely just a coincidence. The repairer though thought it would probably be cheaper to buy a new one rather than attempt a repair ( he doesn't sell them though just repairs them )
He did test the ac adapter and it was 12.25 whereas I tested the new car charger and it was 13.7, as mentioned above there was no load on either so the new (cheap) charger may well come down to around 12v when on load.
I have always used a pure inverter with the ac adapter in the past with no issues I just bought the car charger for convenience more than any thing else.

Anyway it's a moot point now as I've bought a new one, a much lighter Acer netbook from OW for $308. ( love the way they do business ! )
I will not be using a car charger in the future though ( coincidence or not ) but will continue to use the inverter.

thanks to all those who replied.
AnswerID: 493382

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