help help help, my battery seems to be screwed but im not sure it could be causing me all this problems. one cell is totally dead but the battery is still putting out 12.5 volts when the engine is off and 13.5 when the engine is on. the thing is that i can start the car. the problem is that if i hit my brakes, turn on the lights or use any kind of accessory, the car shuts it self off, help! is this some kind of security system or something? has anyone else had this problem?

 

That sounds like a loose connection somewhere and not a bad battery. A loose connection will cause a spark and shuitting everything off.

Check your alternator and batter connections to make sure they are clean and tight