2

I've got a Fujitsu Siemens AMLO pro v3515 notebook with a dead power adapter.

I don't know much about voltage and current differences but I have a couple of other adapters from different vendors in my junk stuff, there's one that's close which I am wondering whether I can use with this notebook? Here are the specs for comparison:

Charger Power Input Output
Original 65W 20V 3.25A
Replacement 100-240V AC 19V 3.42A

When I connected it for a while, the notebook powered on normally and the computer booted, but I unplugged it for now. I just want to make sure if it's a suitable one and it will not damage the internal electronics or peripherals of the notebook in the long run.

Improve this question

3 Answers 3

Reset to default
-1

As it's a laptop the battery provides the power (when not connected to the adaptor) and it is an 11V. The external power supply output will be regulated by the battery charging circuitry in the computer to charge the battery and provide 11V to the computer power rails. I'd have thought 19V would do that as well as the 20V. This site has a replacement charger with the following spec 19V 3.42A (65W) Laptop Charger for Fujitsu Siemens Amilo Pro V3515 . If it was mine I'd use it without a worry!

Improve this answer
5
  • The battery does NOT provide power to a laptop running on an adapter power source. This is incorrect. When a laptop battery in removed from a powered on laptop, nothing happens. The charging circuits stop charging the battery altogether when it is full. The computer does not RUN from the battery when plugged in. It reverts to battery when DC current is removed. A battery cannot be charged and discharged at the same time. The chemical reactions in the battery don't work that way.
    – Paperlantern
    Commented Jan 21, 2012 at 23:52
  • Thanks Brian for the information share and the specific link where my similar adapter is being sold for this notebook series formally. Appreciated :)
    – Insaf
    Commented Jan 22, 2012 at 7:50
  • Something needs to be reviewed here. This answer has misinformation in it, it should not be marked as the answer.
    – Paperlantern
    Commented Jan 22, 2012 at 17:53
  • @Paperlantern : I did not say that the battery ran the PC whilst on charge but that the 20V input would be regulated to provide the same voltage to the computer supply rails as the battery. I'd modify the answer but it seems clear enough to me already.
    – BrianA
    Commented Jan 25, 2012 at 11:38
  • 2
    @BrianA "As it's a laptop the battery provides the power". That says to me you are saying the laptop runs off the battery all of the time. Even if you didn't MEAN that, that is what it says. Even less that, this answer is still incorrect as suggesting an improperly volted power adapter "would do it as well" as the properly volted power adapter is BAD advice. The unit needs 20V, otherwise the engineers would have provided a 19V adapter. Yes the Watts are similar, but most Adapters have close wattage (45W,65W,90W). Running it long term in this fashion will not prolong the life of the unit.
    – Paperlantern
    Commented Jan 25, 2012 at 13:52
2

You want to match voltages. It probably won't be good for it to undervolt it for a long time. I don't think it will damage it though but I still wouldn't use an unmatched voltage for too long. Amps are fine though, if it were a 20v 3.42a you could run it as long as you want, the device will only pull what it needs. I think you just happened to stumble across a perfect storm of adapters and voltages that the 19v provides just enough for the 20v computer to boot.

As a laptop tech of 10+ years I wouldn't ever recommend it, but it would be up to you to continue to use it. Adapters are cheap though, personally I would order a new one and MAYBE USE the wrong one for a short time if I HAD to use the laptop in the meantime, but would avoid it if I could.

Improve this answer
2
  • it will probably work, I would do it, temporarily, but I wouldn't recommend it either.
    – Psycogeek
    Commented Jan 21, 2012 at 15:35
  • Thanks Paperlantern for the detailed information share. Appreciated :)
    – Insaf
    Commented Jan 22, 2012 at 7:52
2

Let's calculate the difference between supplies to see how much power they both deliver:

The formula for power is: Power (Watts) = Current (Amperes) * Voltage (Volts) or P = I * V

Original power supply: P = 3.25 A * 20 V = 65 W (as indicated)

The new power supply: P = 3.42 A * 19 V = 64.98 W (with significant digits this rounds to 65 W)

So both power supplies deliver the same power.

The issue is around whether there is enough voltage delivered or too much current delivered. Each electrical component in the computer needs a certain voltage. When you add these all up, your total voltage should be less than the voltage delivered by the power supply. In your case you're providing the laptop with less voltage than it used to receive from its old adapter (and more current).

When the engineer originally designed this laptop they would have selected a power supply that provided more voltage than the laptop needed to provide some tolerance and depending on how easy they wanted to make it for the consumer to modify or expand the devices in the laptop, they may have selected a power supply that delivers even more voltage than the stock laptop needs (this is common with desktop power supplies).

The question you have to ask is how much tolerance was built into this solution -- can you get away with providing 1 volt less (keep in mind at this scale we're talking about a 5% difference which can be significant)? Maybe. Maybe not. I don't know and I can't tell you. The engineer could have selected a power supply that delivers exactly the voltage needed. You won't know for sure unless you can measure it.

Depending on the laptop model you have you can likely pick up a replacement power supply. And here's the kicker, you'll find that the replacement may be a different part and in some cases it is also shared with other models from the same manufacturer. It is possible that it provides different voltage and amperes than your original (I have seen this several times with Dell). In this case the manufacturer knows the device and the power it needs and can make the decision as to whether the power supply is suitable for your model. It might be worth looking into what the replacement supply's specs are and seeing how they compare to your "junk" adapter.

Improve this answer
1
  • Thanks shufler for the detailed information share regarding volts and AMPS. Appreciated :)
    – Insaf
    Commented Jan 22, 2012 at 7:51

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .