I bought one of these - http://www.justlaptopbattery.com/solar-gorilla-portable-solar-charger-for-your-laptop/ Went solar instead of extra batteries because batteries will always have to be replaced quickly if used a lot (which is costly) and they lose capacity from day one.
It all depends on the laptop model and the battery (many laptops can use batteries of different capacity). I wouldn't concentrate on the brand.
The SU7300 series chips will suffice the msi ones come with 8 cell batterys http://www.newegg.com/Product/Produ..._mmc=OTC-Froogle-_-Notebooks-_-MSI-_-34152236 turn the settings low and you get just about 7 hrs of life.
I traded 4 monitors and a gaming rig for a MacBook Pro and one dell U2410 monitor. The mac can easily go 5+ hours with a trading application open.
That's misleading, battery life is dependent on the technology, quality and the user. First and foremost, a lot of laptop users are complete idiots when it comes to the battery inside their laptop. If there's one section that every laptop owner should read in the user's manual it's the one on the battery. Second, most of the better business laptops out there come with the more expensive "smart" Li-Ion battery technologies, mostly because of the fact that the owners are idiots. Sure, these types of batteries can cost close to $200. But, with proper care, which is documented in the user manual, you can get well over 1,000 complete charge/discharge cycles out of them with minimal capacity degradation over the life of the battery. That works out to about $0.20/charge, pretty trivial cost, IMHO.