Batteries can do a lot of things while we’re not looking. The most common way a battery will drain overnight is by leaving a light on or a power adapter plugged in, zapping all your battery power while you’re fast asleep.
Slow engine crank:
When you attempt to start the vehicle, the cranking of the engine is sluggish and takes longer than normal to start.
Check engine light:
The check engine light on the dashboard panel sometimes appears when your battery power is weak.
Low battery fluid level:
Car batteries typically have a part of the casing that’s translucent so you can always keep an eye on your battery’s fluid level. If the fluid level is below the lead plates : (energy conductor:) inside, it’s time to have the battery and charging system tested.(non maintenance free battery only)
The swelling, bloating battery case, check it visually:
If your battery casing looks like this you can blame excessive heat for causing your battery case to swell, decreasing your battery life.
Leaking also causes the corrosion around the posts : (where the + and – cable connections are located.: ) The gunk may need to be removed; otherwise, your car may not start.
Old age/Lifetime first buy date:
Your battery can last well beyond three years but, at the very least, have its current condition inspected on a yearly basis when it reaches the three year mark.
so that is all folks, hope can be helpfull.