Battery issue- 9 cell XPS1647

I have been using my 6 cell most of the time. Its about 9 months old and was showing 16% wear level on HWM, So since at 16% the life was about 1 hour 30 min, I switched to the 9cell- First Charge up last weekend ( it was still in the XPS box from when the machine was new back in May. 0% wear. in 1 week its down to 9% - in one week the battery has lost 9% of its useable charge?

What is the deal here?

 

That happened to me a few years back. I opened a brand new battery that was sitting on the shelf for a year and I saw 9% wear from day one. I think it's natural(if they aren't used as time goes by), but please correct me if I'm wrong.

 

right- but its only 4 months old.. Not a year....

c

 

9% isn't such a big deal! You can't expect it to stay at 100% forever. It should stay around those levels of wear for a while. Remember that heat kills batteries! So keep 'em cool!

 

It's totally ymmv. There are so many variables related, not just time............

 

It's perfectly normal. My 1645 came with the 9-cell. When I first booted the machine it said 0% wear, then after a few days I checked it it was at 10%. It has stayed here for 2 months.

My thoughts are the Windows shows the 0% figure until it has time to calculate what it's actuall wear percentage is.

Li-ion batteries lose capacity from the second they are manufactured.

Interesting reading on Li-ion batteries here.

Namely:

 

Batteries are considered consumables. i.e. They do degrade with time and thus the warranty is only for 12 months from date of purchase.

Its the reason why I am not buying a spare battery just yet. I know it may sit in the bag for 12 months waiting to be used as a back-up. And I know that when I want to use it, odds are it will be stuffed.

I recently purchased a battery for a Lenovo Thinkpad, and its already stuffed ... its less than 9 months old.

EDIT:
I take this back. I just checked the invoice and the battery has lasted nearly 2 years (22 months to be exact).