The standard cells used in many portables these days are the batteryspace lithium polymer cells with 4700mAh. I did some looking and found these: http://www.all-battery.com/polymerli-io ... 30146.aspx . They are 6000mAh instead of 4700. This should add considerable play time to any portable. The kicker is that these are the same price as the batteryspace ones, and you can use a free shipping coupon. I ordered a pair for my n64p, and will let you know how they perform. Note: I believe these are currently out of stock, but hopefully they will get more in soon.