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Battery question

2009 Lexus ES350 79,500 miles

A month ago while waiting to pick up my daughter, I had the radio on for a few minutes while the engine was off. Car would not start while all the electrical worked so had to get a jump. I tested again yesterday by leaving the radio on and the battery dies. Get another jump and start, car starts and runs fine as long as I don’t do anything with the engine off.

Volt meter reads the battery at 12.9 when the engine is off. Jumps up another 2.1 when I start the engine meaning alternator is fine too. Just in case, I bought a new battery but have yet to replace it. Voltage on a new battery reads at 12.64 which is even lower than the old one!

Should I still go ahead and replace it?

If the battery has enougn power to crank the engine when fully charged, it should have enough power to run the radio for a few minutes without going flat, so the symptoms are a bit strange. Try removing and cleaning the battery cable clamps. And since you’ve already bought a new battery, you may as well install it and see if it helps. But I’m suspecting a short or drain of some kind in your radio circuit.

You can check for unusual current draw when the radio is on and the engine is not running by using an ammeter as described here:

Oh FYI, I do have almost 80K miles on this battery.

It’s not mileage, it’s age and heat that kills a battery. Usually 5 years or so is when they start to go weak.

If the original battery is still in the car I would recommend replacing it. You might check the owners manual before disconnecting the battery cables. Many late model cars will lose accumulated memory and even trip the anti theft systems resulting in the the radio and even the engine to fail to operate until reprogrammed at the dealer or a well equipped shop.

The age and the weather, specially heat kills a battery. It’s the cold weather that exposes the weakness. Remember too that a run down battery is seldom brought back to full charge under normal stop and go driving and trips with short duration. If it were mine, I would remove the battery, or disconnect it and put it on a an auto charger over night to bring it back. But, I do agree, batteries never improve with age and the first sign of trouble should be the last time you put faith in it. Unless you live in the south, batteries can last a very long time. I have never replaced a battery in the six cars each run to about 10 years up to 150k miles by trade in time. Give the recharging a shot and take it from there. Toyota puts pretty strong batteries in their cars OEM on at least the models I am familiar with. Have the charging system checked too and clean terminals as suggested.

I would have the battery load tested at an auto parts store, in the mean time take a voltage reading of the original battery with the headlights on. A battery can have good voltage but little capacity left.

Ed B.

Be careful about an auto parts store. Some will want to sell you a battery and adjust their “interpretation” to that end. If you have a place you normally have it serviced at and have confidence in their honesty, go their. Auto parts stores ? I would take a pass.

The 12.64 is normal and perfectly acceptable. Each cell on a good, fully charged battery should have a shade over 2.1 volts so 6 cells X 2.1ish gives you the 12.6 and above.
After being charged for a while (battery charger or car itself) you will likely find that voltage will be a bit higher.

Check the voltage on the old battery while cranking the engine. If it drops below 10 the old battery is likely bad.

I think its just time for a new battery. It is not holding a good charge. Let’s see, 09 to 14 is five years? Thats about it. I replaced my 09 battery a year ago.

Agree to all the above. The reason that your old battery is reading 12.9V I suspect is due to taking a reading right after shutting down the engine. Right after shutdown, the battery can store a “surface charge” that can read as high as 13.2V, but that bleeds off fairly quickly down to 12.6V. It may take a few hours.

As to draining down quickly when using the radio, do you have an optional hi powered amp in your car. Since you have a Lexus, I would not be surprised if you have the premium audio system, that might be putting out 200 watts or more and that will drain a battery quite a bit quicker than a typical 2.5 watt per channel amp in a basic OEM radio.

At 5 years old, the first time I have any trouble with a battery, I replace it immediately. The odds of getting stuck somewhere are very high if you don’t.

Car’s been off for a few hrs and when I measured again, it registered 12.7. But I agree with those of you suggesting to replace. I’m in Chicago and our winters have been brutal lately. Better safe than sorry.

Since you already have a new battery I’d use it. But if the problem continues, and all connections are clean and tight, it could be your starter solenoid contacts. Toyotas are known for that problem. Mine happened around 90k.

+1 for texases. If the battery voltage doesn’t drop when it fails to crank, the solenoid contacts aren’t letting power get to the starter motor. If the battery voltage does drop, but stays above 10V when it fails to crank, the starter motor itself is failing.

Simple voltage checks are not a reliable method to test the condition of the battery. The only way to ascertain battery condition is something called a “load test”. As an analogy, say you discovered could pedal one of those stationary exercise bicycles really fast, but only if you dialed all the pedal resistance completely off. The fact you could get the rpms up to a high rpm with no resistance (load) would be a poor way to predict how well you’d do once a steep hill (load) was dialed in. You might well find you couldn’t move the pedals at all with a load.

If this is the original battery, I concur w/the other that it is most likely time for a replacement. But no harm done taking it to you mechanic and having it load tested first. There is some possibility the battery is still ok but you have corroded contacts or grounds.

It’s unbelievable all the theories that are being floated here

To me, anyways, this has the classic symptoms of a battery that won’t hold a charge, because it’s old and needs to be replaced

In my opinion, the battery is the one and only problem

It’s good preventative maintenance to replace the battery now if it is 6 years old. If you are worried about getting stuck somewhere with a dead battery, this PM is well worthwhile whether the battery is bad or not. It will malfunction much sooner rather than later.

I’m a fleet mechanic, and the vehicles get inspected every 6 months. Certain air brake vehicles get inspected every 3 months

Anyways, I replace all batteries at 5 years, regardless of if they test good. Many of them don’t even last that long. I’m in southern california, so I assume the heat is a big factor

I figure it’s better to actually prevent a service call due to a dead battery, versus trying to get every last day out of it. And then the vehicle operator has a dead battery in the most dangerous part of town, or somewhere very inaccessible

If you think about it, it’s actually more cost effective to replace a battery at a certain age, versus paying for the battery AND the labor involved for the service call. Not to mention the lost productivity of the vehicle operator, while he’s waiting for you to show up with a fresh battery, or get a jump start

I have recently replaced two batteries, one was 11 years old and the other was 10, but I’ve had them last less than a year for me too. A battery only goes dead on me once, then it gets replaced. Been my experience that once one goes dead, it continues to fail frequently after that.


what state do you live in?

I’m in southern California . . . and nobody’s battery lasts 11 years here. 5 years is pretty typical