Upgraded the twins today. T420 got 16gb ram and a sled battery. 9cell + sled = 17hrs battery life. T480 got an extra 16gb of ram, up to 32gb. Happy with the
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HB PLUS Battery for Lenovo Thinkpad T420 T520 T430 T430I T530 T530I W530 L530 L430 6 Cell Laptop Battery - HB PLUS : Flipkart.com