Choosing the Correct Laptop AC Adapter

LJC003

Estimable
Feb 18, 2015
2
0
4,510
0
Hi everyone,

First time posting here; I'm hoping you fine people might be able to help me get my head around the mysteries of voltages for laptop AC adapters?

I recently inherited an old Dell XPS 15 (L501x) from a colleague which was reported to have issues with overheating/shutting itself off when plugged into AC power. I had a look at the battery (original Dell JWPHF) and power cable (not an OEM power supply) and noticed the following:

  • Battery
    Voltage 11.1V, Amperage 5200mAh.

    Charger
    Voltage 19.5V, Amperage 4620mAh.
I figured that this was probably the root of the issue as it was my (possibly misguided) understanding that the voltage of a laptop battery charger should match the rating stated on the laptop battery itself, and that the amperage of the charger should match or exceed the stated amperage on the battery.

I began looking for replacement chargers but was a little bemused to find that Dell's recommended replacement (spec at this link) seems to state an output voltage of 19.5V.

This leads me to believe that I was misguided in my above assertions relating to voltage and amperage. Can anyone set me right? Any help in getting my head around it all would be hugely appreciated.

Thanks!
 

Someone Somewhere

Dignified
Moderator
The laptop has a built-in charging circuit, so no, you don't need the same voltage on the battery as the charger. Fun fact: Li-ion cells vary from ~3.1V to ~4.1V per cell depending on how charged they are - an '11.1V' battery will vary between about 9.3V and 12.3V.

Batteries are rated in amp-hours, which is a measure of capacity, not current.

I doubt it's a charger issue. Most likely it's full of dust at that age.
 

LJC003

Estimable
Feb 18, 2015
2
0
4,510
0


Thank you for the information! Very useful indeed, although I'm very embarrassed to have confused Ah and A. I really appreciate you taking time out to enlighten me.
 
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