If you're going to get another battery then try to get the official Nintendo one.|
The official battery is at 1300mAH (milliampere-hour) and you may see a replacement battery listed at a higher say 1500mAh. Do not be fooled and go for the higher one, always try to get the official Nintendo replacement, a higher mAh does not neccesarily mean more usage time.
This comes from personal experience when buying replacement batteries for my DS Lite.
#7451382, By Phishfood Battery Life
Phishfood 53 posts
Seen 7 hours ago
Registered 8 years ago