laptop voltage and amp question

hey everyone,
well i just started working on laptops, compaq, compusa, ibm..I know you have to have an adapter to match the voltage and amp on the laptop. If you don't have an adapter for that laptop and you just have to use any adapter you can find, what difference does it make if the voltage and/or amp on the adapter is higher/lower than the laptop. Is more/less voltage/amp better/worse for the laptop and why. or direct me to a site, thanx! oh, the reason is because i sold a compaq presario with 18V and 2.4amp with an adapter from another compaq at 19V and 3.16amp.

According to Toshiba's certification test. Its Ok to be high on Voltage, but do not exceed the amperage. Thats what Toshiba says. It might not hurt the laptop immediatley but over a longer period of time comoponents will start failing

[quote]Originally posted by cc_penguin:
<strong>According to Toshiba's certification test. Its Ok to be high on Voltage, but do not exceed the amperage. Thats what Toshiba says. It might not hurt the laptop immediatley but over a longer period of time comoponents will start failing</strong><hr></blockquote>

According to my qulaifications in electronic/electrical engineering (half a degree), I'd say you've got that the wrong way around. Never, hang on that didn't quite give the correct emphasis :eek: NEVER, EVER, WHATEVER THE EXCUSE, INCLUDING IF YOU HAVE A NOTE FROM YOUR MUM, DOCTOR AND GOD :eek: run anything you're not prepared to turn into a smoke pot about it's rated voltage. Above current could be OK, but take the battery out.

[quote] According to my qulaifications in electronic/electrical engineering (half a degree), I'd say you've got that the wrong way around. Never, hang on that didn't quite give the correct emphasis NEVER, EVER, WHATEVER THE EXCUSE, INCLUDING IF YOU HAVE A NOTE FROM YOUR MUM, DOCTOR AND GOD run anything you're not prepared to turn into a smoke pot about it's rated voltage. Above current could be OK, but take the battery out. <hr></blockquote>

I agree dont do it. Bad bad idea I've seen this happen with user thinking.....no hold on the user weren't thinking when they tried a 24v tosh power supply with a visitors 12v IBM. Whats that burning smell????? Whys my laptop not working?????

D'uh

Cheers
PapaSmurf

[quote]Originally posted by Outcoded:
<strong>

According to my qulaifications in electronic/electrical engineering (half a degree), I'd say you've got that the wrong way around. Never, hang on that didn't quite give the correct emphasis :eek: NEVER, EVER, WHATEVER THE EXCUSE, INCLUDING IF YOU HAVE A NOTE FROM YOUR MUM, DOCTOR AND GOD :eek: run anything you're not prepared to turn into a smoke pot about it's rated voltage. Above current could be OK, but take the battery out.</strong><hr></blockquote>

I dont agree myself, just stating whats on Toshibas Certification test, Ill get the info and post it directly when I go to work on monday for verification.

I went to school for electronics and worked for 4 years doing circuit board repair on monitors, printers and UPS's. I believe that if you're over slightly (~10%) on the voltage, it's ok and will function, but will generate slightly more heat, which over an extended period could burn up a component.

Voltage is constant, if it says 18V it will produce 18V at all times. The Current rating, however, is the maximum it can produce. You're laptop is going to pull as much Current as it needs, so it's not that big of a deal to have a power supply capable of supplying more than your's specifies.

It's like a car battery, they say 12V but I've seen them read as high as 13.7V.

[quote]Originally posted by imarolan:
<strong>Voltage is constant, if it says 18V it will produce 18V at all times. The Current rating, however, is the maximum it can produce. You're laptop is going to pull as much Current as it needs, so it's not that big of a deal to have a power supply capable of supplying more than your's specifies.

It's like a car battery, they say 12V but I've seen them read as high as 13.7V.</strong><hr></blockquote>

It sounded good right until that last statement. {crack open can of worms}

If the rating is 18V constant on the AC power supply, why did you use the automotive analogy to a charging (engine running) 12V DC system pushing potential of 13.7V? Did you intend to imply that the current rating of a laptop would correlate in some roundabout way to the electric potential of a car? That sounds like apples to oranges if you ask me…

hey thanks for the responses. So it sounds like a little over on the voltage is OK, but as far as amps go, you don't want to go over on that. So would it be better to go lower on amps for an adapter

[quote]Originally posted by Ya_know:
<strong>

It sounded good right until that last statement. {crack open can of worms}

If the rating is 18V constant on the AC power supply, why did you use the automotive analogy to a charging (engine running) 12V DC system pushing potential of 13.7V? Did you intend to imply that the current rating of a laptop would correlate in some roundabout way to the electric potential of a car? That sounds like apples to oranges if you ask me…</strong><hr></blockquote>

I didn't say anything about a charging car battery, nor did I mean a charging car battery. I was referring to a car battery removed from the car sitting on a bench. If you've ever bought one, you'll know that batteries come in a wide range of amp ratings, and the higher rating you're battery has, the better the battery is.

If you buy a power supply with a lower amp rating, it may not be powerful enough to power your laptop.

[quote]Originally posted by imarolan:
<strong>

I didn't say anything about a charging car battery, nor did I mean a charging car battery. I was referring to a car battery removed from the car sitting on a bench. If you've ever bought one, you'll know that batteries come in a wide range of amp ratings, and the higher rating you're battery has, the better the battery is.

If you buy a power supply with a lower amp rating, it may not be powerful enough to power your laptop.</strong><hr></blockquote>

By describing a 13.7V rating you were referring to a battery recieving a charge. The most you should see disconnected on a bench from a normal battery is 12.5v. However with the engine running you would see 13.5 to 16.5V, depending on demand and charging system. “Oh yes”, I have bought one before; I even replace my own washer fluid.

But now you refer to amps (wide range) on a car battery instead of Volts; when I referenced your analogy between the Amps of a laptop supply, to the Voltage of a car. Basically you made a mistake an electrical major shouldn't. I’d like to know where you got that comparison, or if you just slipped…

(This really isn’t a flame, just an intellectual debate, please take no offense)

I was up a little late for my brain, but really I was trying to compare it to something common that people could relate to. I'm sorry you're such a stickler, but the point is:

Having a little too much voltage is OK. Having a higher amp rating is also OK. Having a lower amp rating than what you require might lead to a problem.

Think of it this way.

Voltage is the level of power bieng applied to a specific device.

Amperage is the speed at which the device CAN supply the power.

Voltage is constant - ie. 17.2 volt power supply will ALWAYS (when functioning properly) deliver 17.2v (+/- 10%)

Amperage is variable - a 2 Amp device will deliver a MAXIMUM of 2 Amps (+/- 10%) depending on the device demand.

So. Match voltage and do not use a power adapter that cannot deliver at the MINIMUM the amperage that the target device requires.