Thinkpads Forum

I need a second power cable to leave at the office and have got one which I thought was correct but now am not to sure,

My original is thr 65w 20v (which came with the X201) states output - 20v ~ 3.25A

The new one is 90w 20v (from an T400 i think) states 20v ~ 4.5A


Is the new one safe to use or will it kill the battery? I didn't check at first plugged it in for 2 mins and charged as expected but now im not 100% its ok. On the lenovo website it does offer a 90w charger from the X201 but it doesnt state if it is 3.25A or 4.5A.

Thanks,

You can always use a higher wattage AC adapter with no ill effects as long as the voltage output is the same.

Harryc wrote:You can always use a higher wattage AC adapter with no ill effects as long as the voltage output is the same.

excellent thanks,

so tyring to think back to my electronics lessons at school....the amps being different is irrelevent to the charge as long as the volts are the same?

Generally correct. The voltage of the power supply must always match what the laptop was designed for (within a volt or so). The relationship of voltage, amps and power is: Voltage x Amps = Power 20V x 3.25A = 65W; 20V x 4.5A = 90W

The amperage does matter if you were using a power supply that is rated lower than what the laptop consumes. Since the x201 is spec'ed for 65W, connecting a 90W power supply only means that the supply doesn't have to work as hard (hot) to provide the 65W that the laptop may consume. There's also a possibility that the battery will charge faster when used with the 90W power supply since there is more current available, however I haven't actually measured the time differential.

Connecting a 20V supply that's only rated for 40W is bad because you would be exceeding its design capability. That could result in reduced voltage, intermittent operation or a smoking power supply if the laptop is working hard enough to demand the full 3.25A.