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My friend gave me 3 Lenovo Thinkpads and 3 PSU cables and I'm trying to match them up. In particular, the most powerful laptop is a Thinkpad X1 Carbon. On the back it says it requires 20V,4.5A. However, the most powerful of the PSUs says its output is 20V,3.25A.

All of the three laptops and PSUs are physically compatible with each other, ie have the same shaped power plug/socket.

Is it generally ok to use a 3.25A PSU with a 4.5A laptop, if the voltage is the same?

Does the 4.5 mean that is the maximum current it might need?

Will it tend to run slowly as a result of using less current?

thanks,

EDIT - in the comments below this question is referred to: Laptop power supplies, does current matter?

That's kind of different to my situation because in that other question the current difference is larger (8A v 5A, compared to 4.5A v 3.25A in my case).

EDIT 2 - what's pushing me towards thinking it's ok is that this item on amazon https://www.amazon.co.uk/Lenovo-ThinkPad-Genuine-Adapter-Charger/dp/B00HW05MK4, which claims to be a Thinkpad X1 Carbon Charger, seems to be identical to the 3.25A charger that I have.

Max Williams
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  • @KamilMaciorowski not really to be honest, there's quite a lot of differing opinion, with some people saying it might melt the PSU (which I don't want to do). – Max Williams Aug 12 '20 at 14:10
  • @KamilMaciorowski also in that question the voltage differs too. In mine the voltage matches. – Max Williams Aug 12 '20 at 14:11
  • The other question explicitly says `Clearly the voltages are the same, but the currents are different`. Frankly, it looks like you're rejecting it because there's an answer that you don't want to hear. – Kamil Maciorowski Aug 12 '20 at 14:15
  • @KamilMaciorowski you're right, sorry, the voltages are the same. I'm not *rejecting* anything, but that answer makes me nervous about using the adapter because literally the first two lines on the marked-correct answer are: "Using a lower current rated brick (the 5 A on the 8 A laptop) would result in one of the following: Melted power supply or cord, as the laptop starts drawing too much current". That kind of makes me not want to just mark it as a duplicate, and get a more informed opinion. – Max Williams Aug 12 '20 at 14:19
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    In general, do not use a power supply that is rated lower than the device to be powered by it. You can use a power supply that is rated higher than 4.5A at 20V (90W), but not lower. If the device tries to pull more power than the power supply can provide, bad things result, like fires. Find the recommended power supply from manufacturer, and ensure that the power supply you use meets or exceeds the manufacturer adapter. You will need to include the exact model numbers of your devices in order to provide more detailed answer. – Jim Diroff II Aug 12 '20 at 15:02
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    IRS worth checking with Lenovo - often if the brand is the same, the plug is the same and the equipment is OEM/branded and not fake, a smaller charger will work but charge at a slower rate. I've not used Lenovi much, but this is true of at least the older dells, which could detect and slow charge off a 35 watt charger or use a 65 watt one. – davidgo Aug 12 '20 at 20:28

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