My battery is draining much faster than expected, what could be wrong with it? What should I do?

My battery is draining much faster than expected, what could be wrong with it? What should I do?

Certain factors can cause a solar battery to drain much more quickly than the normal wear and tear of use would account for. These are some of the things that can cause a solar battery to drain faster than normal:
Using a battery that was manufactured more than eight months before use. Batteries that have been freshly manufactured will have a much longer lifespan.
Not charging a battery fully before using it. 
Mixing-and-matching different kinds of batteries in one bank. All batteries must be on the same voltage to be used. 
Charging the battery incorrectly (improper amps-to-capacity). 
Allowing batteries to rest unused in long-term storage. All batteries self-discharge over time, so it is important to apply charge whenever the charge level falls below the recommended levels. 
Allowing batteries to stand too long discharged between charges. 
Keeping batteries in temperatures above 35°C. High temperatures increase internal discharge and cause a standing battery drain.
Using deep cycle batteries to start engines. Deep cycle batteries are not intended for this purpose and using them to power powerful bursts of electrical energy (rather than extended duration current) can cause cumulative damage.
Short circuits. Have your accredited solar electrician check the system.

The following methods can be used to avoid a solar battery drain and extend its life: 

Not allowing batteries to stand too long discharged between charges (more than 24 hours in warm weather and more than a few days in cooler weather)
Not leaving a battery in storage without compensating for energy loss. 
Not using deep cycle batteries to start engines
Fully charging batteries instead of partially charging them 
Avoiding storage of batteries in a heat of 95F or higher, which leads to internal discharge