I found a fool proof solution to reset battery wear to zero.

I have a XPS 9550 and a XPS 9350 and have reset the battery wear to zero on both using the same simple method:

Let the laptop battery run down until it turns itself off (do not reboot into windows or boot into BIOS to drain the battery completely as this can actually increase battery wear), then leave laptop off for several hours - overnight even. Reconnect power cable and fully charge until white charging light goes off before powering on.

That's all there is to it, job done!

BTW some say you need to have the battery set to charge in Standard mode but I didn't. The 9550 was set to AC Primary and the 9350 set to Adaptive. Using the method above both successfully reset to zero battery wear regardless of the charge settings.

 

What is the purpose of resetting the battery wear data?

 

Resetting battery wear to zero allows the battery to be charged to its full capacity.

 

My 2016 XPS 9550 tuned up from John Lewis with 10% battery wear from new. I tried booting into BIOS running the battery down to completely empty and recharging and ended up with 14% battery wear.

About 6 months after owning it I took my laptop to my parents house one weekend and used it it until it turned itself off. The following morning I put it to charge without turning it on. Sometime later after it was fully charged I turned it on and noticed the battery wear was magically zero.

I didn't understand what I did to reset it back then, but accidentally doing the same thing again and noticing, then repeating the very same method on a second device surely conforms it?

 

There is a default battery wear of 10% set in Dell bios, so a new laptop/battery will always have 10% minimum wear. Charging a battery to 100% is bad. Charging it to 80% instead of 100% makes it live about 30-40% longer.

 

Are you sure we are talking about the same thing? I am referring to battery 'wear', not the battery 'reserve' set in the BIOS.

My first battery came with 10% wear out of the box however the second one fitted under warranty by a Dell technician in my home had zero wear from new.

 

Yes? Because both are the same. The bios reverse will be shown as battery wear in the OS.

 

My 9550 sits on my desk plugged in almost permanently and so is set as Primarily AC power. This setting lowers the charge threshold (sets a reserve in the BIOS) to extend the life of the battery.

But regardless of that setting, some weeks the battery wear is reported as 14%. Other weeks it shows 2% or 8%. Re-calibrating the battery as I have sets the wear to zero even though I have not changed the 10% reserve set in the BIOS.

 

Surely leaving my laptop shut down when it hits its reserve, leaving it off for several hours, then recharging until the white light goes off does not and can not alter the reserve setting in the BIOS?

Plus, if the battery wear showing in the OS is actually the reserve set in the BIOS why does it change its % value from week to week, rather than stick to 10% permanently?

 

Once it is properly detected though, the OS and BIOS will both not show as wear