Help me understand Li-ion laptop batteries.

February 16, 2009 2:13 PM

I'm about to purchase an aftermarket Li-ion laptop battery on eBay. However, I'm quite confused about the differences in specs for mAh and number of battery cells. Which is more important and how are they related?

This is for a Lenovo 3000 V100 laptop, which from what I gather has a notoriously bad factory battery. At the moment the factory battery won't hold any charge whatsoever.

On eBay, there's a couple of pages worth of third-party replacement batteries. However, I'm really confused by the differences between them.

There are batteries listed that are both 6-cell and 8-cell, as well as some that don't mention the number of cells. On the Lenovo site, they sell a 6-cell and a 3-cell. To my way of thinking, the more cells, the longer the battery life. And that's always the case, right?

However, the mAh rating is what really throws me off. Some of the 6-cell batteries are listed as 4400 mAh, while other 6-cells are 4600 mAh. But the 8-cell batteries also show 4600 mAh.

So is the mAh rating as important as the number of cells? How exactly are the two specs related?

I've googled this a bit, but can't find an adequate explanation.

posted by iamisaid to computers & internet (7 comments total)

(I'm simplifying a bunch here)

A "Cell" can be of just about any size, and the total capacity of the battery is the sum of its cells. What matters is the total mAh rating of the battery. Yes, the more cells the longer the battery life, for a given size cell, but not all cells are created equal.
posted by Tomorrowful at 2:22 PM on February 16

You want the battery with the higher milliamp-hours. The higher the mAh, the longer your device will run between charges.

Number of cells is a red herring.
posted by dunkadunc at 2:22 PM on February 16

The one reason to worry about cells is that for a given battery, the higher cell-count battery may actually be physically larger. Like on Lenovo T-series laptops, the "main" battery (under the screen) can be upgraded to a model with like like 50% more cells (and correspondingly higher mAh and runtime) but it juts out the back of the computer like another inch or something. Other than that, yeah, only the mAh matters.
posted by jeb at 2:42 PM on February 16

could i say "like" more please? I'll try harder next time.
posted by jeb at 2:43 PM on February 16

Which contains more water, a gallon jug or five pint bottles? The latter is "five cells".
posted by Chocolate Pickle at 4:10 PM on February 16

A gallon jug contains eight pints.
posted by dunkadunc at 4:12 PM on February 16

Exactly. The point was that capacity is more important than the number of containers.

The rating in milliamp-hours is the capacity. The number of cells is the number of containers.
posted by Chocolate Pickle at 5:50 PM on February 16