The battery in the LabQuest 2 can sometimes swell up. There are several possible causes of the swelling, including exposure to high temperatures (such as a hot car), defects in the battery, or natural aging of the battery cell.
The warranty on LabQuest batteries is one year. However, if a battery swells within the first two years, let us know, and we will replace it at no charge.
For batteries more than two years old, replacements are sold as LabQuest 2 and LabQuest Stream Battery, order code LQ2-BAT, $19.
To tell the age of a battery, see:
TIL 3773: How to tell the age of a LabQuest 2 battery.
When does swelling become a problem?
While the battery won't always be perfectly square, it should feel firm and should not interfere with the battery door on the LabQuest closing properly. If the casing is obviously bulged out or the battery feels soft, the battery is unlikely to hold a charge and should be replaced.
If you continue to use it, it may continue to swell and can become a safety hazard. The battery should be taken out of service and recycled. For a list of nearby battery recycling locations see:
To increase the longevity of batteries, see also:
TIL 2018: What is the best way to store LabQuest units over summer vacation?