Laptop power supplies, does current matter?

I have two laptops (same manufacture), with the same type of power connector.

However, the power supplies/transformers are slightly different.

The output on the first laptop's power supply is 15.6 V at 8.0 A. The output on the second laptop's power supply is 15.6 V at 5 A.

Clearly the voltages are the same, but the currents are different. I assume the second laptop's power supply can not be used on the first, because it can't supply enough power to the laptop.

However, can the first laptop's power supply be safely used on the second laptop?

Answer

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


• Working laptop, with little to no charging of the battery (or charging the battery, but no working laptop) as 5 A is enough for one, but not the other


• Perfectly working laptop, as even though the brick is rated at 8 A, your laptop only draws 5 A (or the 5 A is perfectly capable of pumping 8 A)

Using a higher current rated brick (the 8 A on the 5 A laptop) should be fine - the laptop will only draw a theoretical maximum of 5 A, so that's the maximum that will be put out by the power supply.

This, of course, assumes that the polarity is correct - otherwise you'll likely just go poof (or unlikely catch fire). Sometimes there's a diagram, sometimes you have to check, sometimes you just cross your fingers and pray (the latter is not recommended for expensive toys like laptops).