The standard battery is a 6-cell Lithium Ion battery (56WHr). An optional 9-Cell battery (85WHr) adds weight and sticks out from the XPS M1530’s sleek silouhete, but will last 31% longer. I recommend getting at least one extra battery if you’re highly mobile, such as doing cross country flights, the 9-cell is what you’ll want. If you’re just bopping around town or campus then the 6-cell should suffice. If you’re at a desk all day then the 6-cell is best since you won’t need battery life anyway. One good option is to order one 6-cell and one 9-cell battery.
I got a 6-cell dell xps m1530 battery and the optional extended life 85 whr 9-cell replacement dell xps m1530 laptop battery. Using the 6-cell battery under normal usage (office work and screen brightness at half) I got around 2.5 hours of battery life, which isn’t bad. With the 9-cell it was an hour longer at 3.5 hours.