When you first log in, you might see a message that says:
Battery may be broken. Your battery has a very low capacity which means that it may be old or broken.
This message is displayed when the computer detects that your battery is not capable of storing much charge. The most likely reason for this is that your battery is old; it's probably not broken, so there's no need to worry.
Over time, all laptop batteries lose their ability to store charge. After a while (normally a year or more), the battery will only be able to store a fraction of the charge that it could when it was new. The message above is shown when this happens.
If your computer/battery is relatively new, it should be capable of holding a high percentage of its design charge. If it can't, then your battery may be broken and you might need to seek a replacement.
See for instructions on how to check your battery's capacity.