coppens1

Lexus Forum 291023 Draining Battery

Dear Forum Members, I am having trouble with my 2001 Lexus ES300 with a draining battery. I have had the trouble before and replaced the battery. The service center said the charging system is OK.
Now with a NEW BATTERY, it went dead a few days ago. So I put my trickle charger on it, and charged it up. This time I decided to keep track of the voltage.

Here's the data:

10.26.23 Voltage 12.49
10.27.23 Voltage 12.23 car not started 26-27 Oct
10.28.23 Voltage 10.17 car not started 27-28 Oct
10.28.23 Voltage 12.49 (after short drive)

From 10.26.23 to 10.27.23 the car lost only .26 Volts.
From 10.27.23 to 10.28.23 the car lost 2.06 Volts!
What could be discharging the battery down 2.06 volts, when sitting 10.27.23 to 10.28.23, with a NEW BATTERY!

Has anyone else had this problem?

LeX2K

Need to know battery voltage with a running engine.

coppens1

Dear LeX2K, at 3 PM 11.08.23 with engine running, the voltmeter showed 13.65 volts at the battery terminals

LeX2K

Next step is measure current draw when the car is off. Do you have an amp clamp like this?

13.65 volts is fine but was that with no accessories on like headlights, rear defroster, blower motor ect?

coppens1

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No accessories were on when I took the measurement. I took the measurement with a standard electrician's voltmeter. I can take it again with headlights and air cond on. That would be the only accessories used most of the time, this time of year in Florida.

Oro

While you are at it, use the multimeter to look for ac voltage across the battery terminals when running.

If you see more than a few mV, the Alternator has bad diodes. They can drain a good battery overnight. If the shop just looked at the charging voltage and not a full diagnostic of the alternator, they would have missed it.

This trips up people all the time and helps sell a lot of unnecessary batteries. Not that I’m sure it’s your problem, but it’s worth checking when good batteries go flat..

coppens1

Dear LeX2K, I tried pulling the 2 fuses for the music system, but it had no effect. I have currently pulled the fuse for the air cond and driver's seat to see if that has some effect.

Dear Oro, I will try your suggestion about looking for ac voltage across the battery terminals when running. I assume the procedure is to have the engine running, set the voltmeter for alternating current, put the terminal probes as usual, and measure the mV. I will let you know. JC

coppens1

Dear LeX2K and Oro, the car had a brand new battery from Walmart. Last week the new battery went dead while the car was parked at the library, about an hour after driving, and 3 hours after charging with a 3 amp charger! So I took it to Advanced Auto Parts for testing battery and alternator. Alternator tested fine, but battery no good.

I bought the new battery 3 months ago, and it went bad after 45 days so was replaced again. Now another 45 days later and the brand new battery failed again. Now I am on the 3rd new battery.

Moral of this story is to keep trying and don't rule out ANY ANOMALY. So next time it happens, I will have Walmart check their battery before I do anything else.

LeX2K

What brand of battery? First rule of diagnostics is never assume.

Oro

What did this test show (value range)?

dirac1254

Did you have any 3rd party accessories added by either yourself or a previous owner? For my ES300 the previous owner installed some fancy speaker system that was slowly draining my battery. So if not driven a decent amount after a couple days my battery would be dead. I disconnected the speaker after I discovered the issue if you're wondering.

coppens1

Dear Forum Members, I have found an interim solution to my problem of a draining battery, that has plagued me since July of 2023. I left my car with an Auto Electric shop with multitudes of diagnostic equipment for several days and they could not find the problem.

I went online and bought a Battery Isolator for $4, which disconnects the battery from the electrical system, when the car is parked. You only have to turn a **** on the device, installed on your battery, to disconnect.

I have used it for 2 weeks, with NO DEAD BATTERY. Eventually, when whatever is causing the problem fails, I will get it fixed. JC

Catanzaro

Where did you install it? Do you have a part #? Thanks!

coppens1

Dear Catanzaro.
It installs right on the battery terminal. I bought it online at TEMU.
Battery Circuit Breaker Switch $3.48
Battery Circuit Breaker Switch Battery Main Switch Isolator Green **** For Car Truck Boat Vehicle Battery Power Cut Off Quick DisconnectGreen×1$3.48By
I can send you a photo if you want.
Disadvantage is you have to open the hood to turn it on or off. JC

Arsenii

To be honest I would really be concerned with what a fire hazard one of those is, considering the current that would go through it, especially when the starter is engaged. There is a reason why proper termination switches are as expensive as they are, it should be something to consider.

Hope this helps and best of luck!