Choosing the Correct Laptop AC Adapter

[LJC003]

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]

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]

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.

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.