1. Most Dell batteries are 300 cycle rated. If this is over a year old then you want a new battery.

2. Some Dell machines have a BATTERY CALIBRATION feature or procedure. This is not an offer to find this for you. Ask dell or get to dell.com and read the docs, ask Dell, etc.

If this battery is over a few years old, there is a worse problem. As the battery ages and fails it can fry the charging circuit. How would you explain to the many folk out there than an old battery is not a good thing.
Bob