How is the best way to use Battery? Nintendo DS ...

Li-Ion batteries don't have the "memory effect" Ni-Cd batteries had. That means that you can charge them no matter how charged they are, however, a battery has a limited number of charge cycles. I'm waiting for the battery to be almost fully drained before I recharge it.

As for the MAC vs PC issue, There are some Windows laptop which can get to approx. 5 hours of use, it depends on the battery, specifications of the laptop and the power configuration of the OS, and of course if your running a DVD movie don't expect to get more than approx. 1.5 hours.

You must fully charge and discharge every now and then for all batteries to get the best from them, if you want a nitendo DS battery try here

nintendo DS battery

does it depends on battery type?

Of course, Expensive batteries will usually protect your widgets better  no matter what you did.

and why do Apple computers can survive on battery near 5 hours while PC/Windows computer can hardly survive 90 minutes?

The LCD ,Hard Disks and CPU will cost less energy, and battery itself may be different.

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