If the battery in your Toshiba Dynabooki Qosmio laptop is no longer holding a charge, you probably need a new one. Lithium-ion batteries, while superior to older batteries that were nickel based, typically will show signs of deterioration after 3-5 years. Our fully compatible, brand new Toshiba PA3788U-1BRS battery replacement is built to meet the original manufacturers specifications and perform just like the factory issued battery. The only difference is the lower cost, which makes these laptop batteries a great value. Its rated at 10.8V with a capacity of 4400mAh, and is designed for the Dynabook Qosmio T851 and other Qosmio models. For a complete list, see By Laptop Models. You can also view a listing of compatible part numbers. If you need additional help finding a compatible battery for your computer system, contact us and one of our customer service representatives will be happy to help you. To get the longest lifespan from a lithium-ion battery, it is recommended that you recharge it when its at 20-30 percent of its full capacity. You should also make sure to regularly calibrate the gauge so your battery meter will display the correct amount of power remaining. If youre planning on watching DVDs or playing games on a long flight, you should bring along a spare battery, as these types of programs can be especially draining on a battery.