Troubleshoot Laptop power supply question

[uninfected1]

Briefly explain your current issue(s)

Replacement power supply required

Steps taken to resolve, but have been unsuccessful

Looked at the charger/adaptors stated below

I've got an ageing Acer Aspire 6930G laptop and the charger/adaptor needs replacing. The output of the original is 90 watts, 19 volts, and 4.74 amps, but these are quite expensive. Would it be possible to use a charger with the same voltage, 19W, but with lower wattage and amperage, 65W and 3.42 amp, as these are much cheaper? Any help really appreciated.

 

[Digerati]

No. Don't do it. You can always go higher but not lower. If we were only talking about a battery charger it would not be a problem. It would just mean it would take longer to reach a full charge.

But these devices are also power supplies. And a power supply must always be able to support the load of the device it is powering. And in the case of a power supply/charger, it must support charging the battery while also powering the computer.

One thing you might consider is a universal power adapter. I keep one in my tool bag for house calls. So far, I have not had a notebook it did not work with. Some are only 65W so avoid them. Make sure it is at least 90W with 14V.

 

[BoraMurdar]

In a nutshell:

• The following will cause damage to your device:
  • Reverse polarity
  • Higher voltage adapter than device rating
• The following will cause harm to your power cord or adapter:
  • Reverse polarity
  • Lower current adapter than device rating
• The following might not cause damage, but the device will not work properly:
  • Lower voltage adapter than device rating
  • Higher current adapter than device rating

Again, this happens 50:50
So, try getting the adapter with similar wattage/amperage/voltage. In the end, the laptop's safety is the most important.

 

[Digerati]

Higher current adapter than device rating

No, higher current will not cause damage as long as the voltage, connector, and polarity remain the same. The battery and computer will only pull the power (voltage x current = watts) they need, not what the supply can deliver. This is why you can use a 1000W power supply in a PC that only needs 300W.

 

[uninfected1]

Great replies guys. Let me just check that I've got this right. As long as the voltage is the same as the original, it doesn't matter if current and wattage are higher, but they mustn't be lower. If I've got that right then that's quite useful because I've seen a 120W universal adaptor at a fairly reasonable price.

Also what do people think of non OEM adaptors? I saw this one (I'm in the UK). Would this be OK or would you advise against it?
https://www.amazon.co.uk/dp/B008WMP...colid=ES2OSIKQER4J&psc=0&ref_=lv_ov_lig_dp_it

 

[BoraMurdar]

No, higher current will not cause damage as long as the voltage, connector, and polarity remain the same. The battery and computer will only pull the power (voltage x current = watts) they need, not what the supply can deliver. This is why you can use a 1000W power supply in a PC that only needs 300W.

Yes, you're right. Correction.

 

[Digerati]

Yes, you're right. Correction.

No problem.

Let me just check that I've got this right. As long as the voltage is the same as the original, it doesn't matter if current and wattage are higher, but they mustn't be lower.

Not just the voltage, but the polarity on the connector too. That is, the positive and negative must be in the same orientation.

Also what do people think of non OEM adaptors?

IF they are of the same or better quality, and all other specs are the same (or more for current) then no problem.

 

[uninfected1]

Not just the voltage, but the polarity on the connector too. That is, the positive and negative must be in the same orientation.

How do I know that before buying?

EDIT: the 120W power supply I mentioned earlier states on the packaging that polarity cannot be reversed so seems fine for me.

 

[tim one]

Fully agree, even when I use my laptop connected to electrical line, then with its (original) power supply, it heats enough, if I were to use a depowered PS, it probably would overheat and melt due to the power required by the laptop.

 

[Digerati]

How do I know that before buying?

Good question. You really just have to take the published specs at their word.

if I were to use a depowered PS, it probably would overheat and melt due to the power required by the laptop.

Some thermal protection device should trip or blow before anything melted. You likely could charge the battery as long as the notebook was not turned on and drawing power too. But if the supply was underpowered and tried to boot the computer, it likely would not boot at all. But this assumes all thermal and overload circuits and devices are working properly and not faulty.

 

[uninfected1]

Excellent thread and it's pretty much answered all the questions I had about buying a suitable power supply. Thanks a lot for all the detailed information @Digerati.

So to summarise, the golden rule is that voltage must always match what is stated for the machine, and if in doubt about amperage and wattage, go higher but never lower. In fact, my original power supply ran quite hot so going higher might be better. And polarity should never be reversed.

EDIT: After I started this thread I found this article which sums things up pretty well. I should have done a bit more googling before posting
Can I Use a Power Supply with a Higher Wattage Rating on my Laptop? - Ask Leo!

 

[Digerati]

Just to clarify something. When it comes to amperage and wattage, when the voltage remains the same, amperage (current) and wattage (power) are directly proportional.

This is because the formula for power is straight forward and dictated by the Laws of Physic. Watts = Voltage X Amps. So with the voltage remaining constant, if amps change, the watts will change proportionally - every time.

So when researching power supplies you don't have to look at both watts and current and worry that both are correct. One or the other will do.

 

[uninfected1]

Just an update. I got a 120W universal power supply and it is working very nicely and not getting hot like my previous one. I have also noticed an improvement in performance. CPU is not maxing out as it had been quite often and there are fewer freezes.

Why would this be the case? I should add that the previous power supply was fairly badly damaged and the wiring was frayed and exposed in a couple of places.

 

[Digerati]

There is no reason the new power supply would affect performance. So I suspect it just seems like it. With the old or new supply, it is the notebook's internal voltage regulator circuits supplying and regulating the power to the systems components. So they would not know what supply is connected.