dead car : battery / something else ?
 

Hi All,
Faced a dead battery and below are the steps I followed

Car did not start in evening as if battery was dead.
Called road side for a jump start.
They tried to jump start but no use.
So, instead of giving the possitive of external battery to possitive of car battery, he gave it to possitive terminal sitting in the fuse box of the car.
Car came to life now.
Drove around a bit so that alternator can charge the car battery
Got home; turned off the car and tried to turn it back on.
No internal lights; nothing;car dead again

Any help on where to start trouble shooting or what could be wrong will be really helpful.

Thanks in advance

Most likely a defective battery. I am surprised the road side assist didn't test the battery. Have the battery tested under load. Most auto part stores will do this for free.

Usual process with any vehicle is to test the battery first. If it checks out test the alternator.

Most like your battery is too old or defective that it won't charge anymore.
Go to Costco and buy a new battery and drive it for a day. If it is OK, then it is just the battery.
If after a day of driving the car won't start with the next battery, then it is most likely the alternator.

It is probably the battery. I doubt it is the alternator....if the alternator was bad your electronics probably would have acted funny when you drove it.

thanks all for your replies to my naive question.

Yes, the road side did not test the battery.

1 more question regarding the above quote -
so, when I started driving my car, for the first 2 mins or so, the brake light, the vsc, the maint reqd light were coming on .... once I revved up the engine, the lights went off, things started looking normal again....would this rule out alternator problem ?

I will, of course, go get the battery tested and update what corrects my issue.

Thanks again to everyone

A Lexus will light up a million warning lights for you, if the alternator is going south. I would've dashed out long ago to buy a new battery. If they get long in the tooth, batteries develop internal shorts and start behaving in a way which will baffle a magician. On the other hand, I've never heard of a Lexus which you have to rev to get warning lights to go out. So one cannot rule out that you have a negative earth cable that's not making the good connection it is supposed to do or for that matter any other relevant wire that is not making good contact.

I've never had an alternator go out, it's always the battery, or maybe a cable in some cases. I replace my batteries every 3 years. I've never been stranded when I stick to that schedule.

If the battery has a shorted cell, it can load the alternator down causing a low voltage condition, hence the lights.
After replacing the battery the terminal voltage should read 13.5 to 14.5 volts with engine running. With engine off the battery should read 12.6 volts. If the voltage while running is less than 13.5 with new battery the alternator is probably toast.

If a battery fails, replace it. I don't understand trying to squeeze more time out of a battery that has let you down even once. If it's under warranty get another one, if it's old spring the hundred bucks and replace it

I am having the same problem with a brand new battery. Has anyone actually solved the problem? What did you do? JC

Check for power "leaking" when car is turned OFF and locked. Something is killing the 12v battery.

inded i concur with others; its most likely the battery; but if u see the battery light come on while the vehicle is running then thats a sign that the charging system is failing which is time to have the alternator looked at.

You could also have a badly corroded battery cable where the wire going into the terminal clamp is corroded.

Battery going dead
 

Dear iMSQ, matts6887,and DennisMik, I have checked all those things. It is a brand new battery, there is no corrosion, and I have had the car checked by 2 different auto electric shops.

It still goes dead if I let it sit for a few days. I will check the 'seat set' buttons again, but I looked at them and they appear OK. JC