Which battery for T420s?

[siLc]

Recently bought myself my very own ThinkPad - a T420s. It came with a broken screen and was parted out. Having been a laptop repair tech in the past, I sourced all the missing parts and put it back together again, all except for the battery.

AFAIK the original T420s battery was the "66+": http://support.lenovo.com/en_US/product ... MIGR-76760
But it seems it has been replaced with what is known as "81+": http://support.lenovo.com/en_US/product ... D=PD024288

Are there tangible differences in longevity if I go for the 81+ ? My previous Dell D630 original battery lasted for 5 years and lost only a half of its capacity.

[EOMtp]

No difference in longevity. The new 81+ batteries have a DRM chip required for charging in 2012 and newer machines. See below:
http://forum.notebookreview.com/lenovo/ ... eries.html

[FunkyRes]

I've been swapping batteries between my T520 and T410 no problem. I guess the battery in the T410 must have the chip my T520 needs?

[siLc]

No difference in longevity. The new 81+ batteries have a DRM chip required for charging in 2012 and newer machines. See below:
http://forum.notebookreview.com/lenovo/ ... eries.html

Oh, I see. So 66+ it is.

I've been swapping batteries between my T520 and T410 no problem. I guess the battery in the T410 must have the chip my T520 needs?

Its because batteries at that time didn't have such restrictions.

[FunkyRes]

My T520 though was bought in 2012.

[siLc]

My T520 though was bought in 2012.

But its still a 2011 model. EOMtp said the restrictions apply to 2012 models eg. T530 and beyond.

[siLc]

Thought I write a little bit how the battery purchase went.

Found a new 66+ on eBay, shipped from Singapore and cost about 1/3 to 1/2 the price of a genuine battery bought locally. Expectations were high, free shipping took 3 weeks but it finally arrived. As thought, it wasn't genuine but now having tested it - in Power Manager it shows as genuine and with an estimated minimum-brightness runtime of 4-4.5 hours. Funny thing, though - it says first use date is somewhere in July 2011 and it has 43 cycles on it. Hoping it lasts...

Now I'm looking at getting a Ultrabay battery. Any words of wisdom?