Last week I posted about a dead battery, had it jumped, took it to Lexus, and they found nothing wrong. Well, it happened again yesterday. Same scenario:

Wife drove about 15 miles to school (where she works)
Turns off engine. Exits car, opens trunk with key fob. Gets her stuff and locks car with key fob.
Comes back 8 hours later. Battery completely dead.
AAA comes and it's so dead that their booster battery doesn't have enough oomph to start it. They have to join in another car battery to get it started. Drove it home (about 30 min) and it starts up fine.

Interesting that the car was unlocked when she got to it in both instances. I would have thought the locked car would stay locked and, as dead as the battery was, she would have had to use the manual key to get in. This makes me wonder if a relay is sticking in the process of locking the car (i.e. car never locks in the first place and drains the battery trying).

I drove the car for 1.5 yrs before she started driving it and nothing like that ever happened. The first incident happened less than a week after she started driving it and the second happened a week or so later. Nothing was left on to drain the battery. The only difference I can think of is that I NEVER used the key fob for anything. I always used the buttons on the doors/trunk. Again, I wonder if the key fob relay could be sticking . . .

 

Women drivers?

 

LOL - can't go there!!!

I'd love to blame it on something she's doing. But, I don't think so. I tried reproducing it with the key fob. So far, seems to work fine.

 

lol again? you going to bring it to the shop again right?

 

how do you use the manual key to get in?

 

How do you know it was a 'dead' battery? A few observations:

It takes next to no power/amps to unlock doors, turn on headlights, etc.
It takes a lot of power/amps to crank an starter/turn an engine over. Thats why batteries have amp cold cranking amp ratings. A diesel engine requires tons of power to turn it over.

So, it is quite conceivable that you could unlock doors with the remote, with a 'dead' battery but not have enough to crank the engine.

It is relatively easy to test a battery using something called a load test. Basically it puts a big draw on the battery like that required to start a car. If Lexus performed the simple test and it passed, then the battery is likely good.

That leaves a couple of things.

Is the alternator charging the battery? Again, this is a relatively simple test for a mechanic to do.

Did you do any mods to anything electrical? If so you could have a 12v draw, which is like leaving your headlights on all day.

Another thing to consider..maybe its a bad starter. I had that happen on a MR2. Wouldn't turn over, jump start or anything. It only happend when the starter motor stopped spinning on the bad spot in the motor...Had the starter replaced and voila..problem solved.

Again..any mods to anything electrical?

 

Right beside the driver door handle there is a cover that you can pop open for the manual key

 

You pop the cover off the door handle and put the mechanical key into it just like a normal door lock

 

How do you know it was a 'dead' battery? A few observations:

It takes next to no power/amps to unlock doors, turn on headlights, etc.
It takes a lot of power/amps to crank an starter/turn an engine over. Thats why batteries have amp cold cranking amp ratings. A diesel engine requires tons of power to turn it over.

So, it is quite conceivable that you could unlock doors with the remote, with a 'dead' battery but not have enough to crank the engine.

All true. We know the battery was dead because she couldn't open the trunk. When she opened the door, no dome light, not even the LED on the start button would light up.

It is relatively easy to test a battery using something called a load test. Basically it puts a big draw on the battery like that required to start a car. If Lexus performed the simple test and it passed, then the battery is likely good.

The first time it happened, I took it to Lexus. They had it all day and tested everything in the battery/charging/electrical system. They found nothing wrong. Even this time, in the amount of time it took her to drive home (about 30 min), the battery charged up enough to start it the next time.

That leaves a couple of things.

Is the alternator charging the battery? Again, this is a relatively simple test for a mechanic to do.

Lexus checked the alternator. Plus, the fact that it charged on the way home implies that the alternator is working.

Did you do any mods to anything electrical? If so you could have a 12v draw, which is like leaving your headlights on all day.

Bone stock. Nothing plugged into any of the accessory sockets.

Another thing to consider..maybe its a bad starter. I had that happen on a MR2. Wouldn't turn over, jump start or anything. It only happend when the starter motor stopped spinning on the bad spot in the motor...Had the starter replaced and voila..problem solved.

Unless the starter can drain the battery while the car is sitting, it isn't the starter. Battery was completely dead in both cases. Of that I am sure.

Again..any mods to anything electrical?

None.

 

Your battery could be coming to the end of its life. Easiest solution is to replace it, it is probably time. Doubt there is anything wrong with the electrical system.

 

Could be. I'd like Lexus to come to that conclusion - since it's still under the 4/50 warranty and the battery is covered until Jan, 2010.

 

So this is what could be happening...... If you turn off your car before you put it in Park and then put it in park, the car seems to be OFF, but the lights are still on. Even though you lock the car (it doesn't matter if with the fob or the button) the lights will stay on. So maybe ask your wife if she accidentally turns off the car before putting it in park?

 

Any decent load test should find a battery on its way out...Pretty interesting dilemma. I wonder if it as posted..perhaps the lights were left on..would def drain the battery

 

It's remotely possible there is a fan relay not shutting off until power dies. But if Lexus has checked the car, they would have found this pretty easily.

Sounds more like a shorted cell in the battery to me.

 

I have just gone through the same issues as you have.

Battery just kept on going out.

Finally had AAA guy check the charge going to the battery--that was fine.

After we let the car run for 10minutes, he tested the battery--turned out the battery cold crank amps were lower (400) than the recommenced 500+ for our car.

Went out and replaced the battery (80bucks)--Seems like it starts up fine now.

If anything else happens with the battery not being charged, there is definitely a voltage leak somewhere.

BTW... GROUP Size 24 ------- for is350