Feb. 20, 2016 Ben Carson greets people at the Beacon Drive-In restaurant in Spartanburg on the day of the South Carolina Republican presidential primary. Jabin Botsford/The Washington Post Buy Photo
If your battery is unhealthy after less than 6 months you should try to get a replacement from dell. You have posted to a forum that requires a moderator to approve posts before they are publicly available. A 9 cell battery usaully last around 4-6 hours.
I don't know how long the batteries will last in your outdoor solar light units. However, I have been using rechargeable NiCad batteries for bicycle lighting for many years. Based on my experience, you can expect the batteries to last 2 years at a minimum.