My dear friend Steve is a very smart guy and he has come up with a gem of post that explains how to take good care of your batteries.

If you try to stop charging around 80% and never drop below 30%, you should be able to double the battery’s service life…..Stay away from third-party chargers.  Not only are you likely to shorten battery life, some have proven to be serious fire hazards ….. Temperature is important.  Below about 40°F capacity drops dramatically.  Heat is another matter.   Anything over about 95°F (35°C) will begin to cause permanent damage.

The whole piece is worth reading!