Bad battery or a parasitic drain
Yes. More so if it is connected. Most vehicles today put a parasitic draw on the battery that will drain it down over time. Parasitic draw should be under .050 mA.
If the defect is causing a parasitic drain, yes.
Dead cell in the battery, or parasitic drain from a light that is on or a relay that is stuck.
Bad battery, Parasitic drain.
There's a parasitic drain somewhere.
This is caused by one of two reasons. Either the battery has a dead cell and needs replacing or there is a parasitic drain on the battery. The drain can be any light that is constantly on or a relay that is stuck.
A PARASITIC LOAD IS A SHORTED POSITIVE WIRE GOUNDING TO THE NUETRAL ON YOUR AUTOMOBILE BATTERY. A RAW WIRE IS DRAINING YOUR BATTERY. GOOD LUCK TRYING TO FIND IT.
The battery can be brought to many shops for a free test. Otherwise, you can test the voltage and parasitic drain amperage with proper usage of a multimeter, available at most hardware and electronics stores. To test the battery beyond voltage and parasitic drain, a very expensive piece of machinery is required to test it further. Most shops have such equipment.
You either have a bad battery, or a parasitic drain in your system. With your vehicle and all systems shut off, measure the amperage draw from your battery with a multimeter. The absolute most it should be drawing in this state is about .5 amps, and that's for the clock radio memory. If you're drawing more amperage than that, you have a parasitic drain in your system, and will need to trace and isolate it.
They wear out over time, there could be a parasitic drain on the electrical system, something might have been left on.
A battery drain on a 1993 Lexus SC300 can be identified by inability for your car to start.