I have owned a lot of laptops, toughbooks, Dells, Gateway, HP, IBM, Sony, Acer and the list goes on.  I have to say that Toshiba tops my list of PC laptops.  They usually have plenty of USB, Firewire, SD slots, whatever you might need, its there.  They are sturdy, reliable high quality notebooks.  No matter what brand of notebook or laptop PC you buy, you will eventually need a new battery.  You can go cheap, but I recommend spending a little extra and getting some decent battery life.

Tip #1 Buy a Lithium Ion – LiON batteries are now used in most new laptops. Unlike the NiMH battery, LiON laptop batteries have no memory effect. LiON batteries are also lighter than both NiCd and NiMH notebook batteries. Both of these advantages equal out to the Lithium Ion battery being the most popular and most expensive among the various notebook power sources.

Tip #2 You can purchase a battery for around $120-$150 which will get you up to 2-3 hours of extra battery life. The better ones have the capacity to give battery life of 7 to 10 hours and cost anywhere from $300-$500.

Tip # 3 Don't limit yourself to the manufacturer, look at Amazon and eBay (I prefer Amazon) as well.  They usually offer better pricing

Tip #4 Get a laptop base with a cooling fan. High temperatures have an adverse effect on laptop batteries. Extreme heat can cause the battery to discharge prematurely and can eventually lead to battery damage.

 In the measurement of battery technology, there are four kinds common method (open-circuit voltage measurement, Coulomb calculation, impedance measurement, integrated look-up table method), usually using a combination of methods to one of the main method of supporting the rest of the way computing power.

The first one is the impedance measurement, measuring its resistance to get the remaining battery capacity value.

The second one is the open circuit voltage measurement, this method is that measuring the battery voltage under static values to calculate the remaining battery capacity, but as a result of stationary lithium-ion battery voltage and remaining capacity relation is non-linear, so this method measured valueis not accurate, the vast majority of mobile phone batteries are calculated using this method

the third is a comprehensive look-up table method, by setting up a related form, the voltage, current, temperature and other parameters, you can query the remaining battery capacity.

The fourth one is Coulomb calculation, the method is by measuring the laptop battery charge and discharge current, the current value and time value After the calculation of product integration has been carried out by filling the battery into the power and the release of electricity, Coulomb's method is a accurate method of calculating power.

Notebook batteries can be 6-cell or 4-cell, meaning that there are that number of battery cells inside the battery. The batteries cells conenect together, the battery capacity reduce reason is that: all the batteries quality and discharge rate can not be in the same level. After discharge, one battery cell capacity in substantial reduction, in order to maintain voltage stability, the battery management chip will be according protection of core power as the "bucket principle", so after the electricity charge will decrease.