How to check the mAh or Voltage for the laptop battery

OK. After some digging, a typical mobile PC (from 2006) can handle 18V to 7.5V at the input either from an AC Adapter or a Battery. Also, the typical voltage for a battery is 11.1V or 14.8V depending upon the numbers of cells. The risk that 14.8V won't work on your laptop is extremely small.

Your laptop supports:

• 71 Wh, 4800 mAh (8-cell) Li-ion battery pack
• 44.4 Wh, 4000 mAh (6-cell) Li-ion battery
• 29.6 Wh, 2000 mAH (4-cell) Li-ion battery

Typically, laptops can work over a pretty wide range of input voltages. 14.8V doesn't sound too high to me. I can't find any specs from their website to confirm that 14.8V is OK, though.

Going from 6 to 8 cells will increase the voltage proportionally. Think of going from 6 to 8 AA batteries.

Here is an article on Notebook Battery Cells that presents an 8-cell battery being 14.4V as pretty common.

As far as battery technology for a laptop, what you've got is what you're stuck with for the most part as the charging electronics to different battery technologies are internal to the laptop itself.

That said, you've asked good questions about the terms used to identify batteries - mAh (yes, milliamp hours) and W (watts).

Watts are a standard way to measure power output of any electrical device. The best measure for a battery would be in Watt-hours, measuring actual energy capacity of the battery. (Watts = Volts * Amps)

A second-best measure would be the mAh measure which would indicate how much current the battery can supply over time at the specified voltage. (I used this figure frequently when selecting AA rechargeable batteries.)

I've not heard about voltage variations between batteries. Essentially the most efficient battery will be the one with the voltage that best matches what the computer's internal electronics were designed around. Any excess will be frequently lost as heat as the internal electronics convert the voltage to the proper level (which is probably not a figure specified by the manufacturer - they're more likely to supply a figure denoting the range of voltages the laptop will accept).

Bottom line for most batteries is that shelf-life is still a factor, so look for a reputable dealer with an indication of when the battery was manufactured since an older better specified battery may not have the capacity of a new battery with poorer specifications.