What? Your car's electrical system is 12V nominal. You measured 12.16V -- how is that "26%"? You need to measure cold cranking amps (CCA), not voltage, to determine the charge.

 

Actually, the nominal voltage of a fully charged battery is 12.6V. Battery testers (including the one I use) translate voltage to "state of charge".
There are many websites that explain all this. For example, see https://www.centurybatteries.com.au/...g-battery-life

 

OK. I wrote "system", meaning the voltage required by the lights, window motors, starter motor, etc., however, I take your point about the fully charged battery voltage, and the maintenance tips.

However, the fully charged battery on my riding mower will measure 12.6V, probably. But it won't start my car. Its the amperage that spins the engine, using the starter motor. I remain very skeptical that your car battery is performing as per its CCA rating, even if it is possible to charge it to 12.6V.

 

The technician at the dealer claimed that he measured the CCA and the result was around 700 (the battery is rated at 630). As I wrote earlier, the battery continued to easily start the car for a whole month despite being driven for an average of less than 10 miles per week (at least two short trips per week so the car was started at least twice per week), with no other charging. An independent mechanic I consulted also thought that there is nothing wrong indicated by the evidence I have. Hence, I don't have any objective evidence that indicates that the battery or the rest of the electrical system is faulty.

 

I have and use a Deltran "battery charger and maintainer" (AKA, a battery tender). It is not practical for me to keep it always connected. Hence, I use it to periodically recharge the battery. This is what I was referring to in my "conclusion" that it would be prudent to recharge the battery every couple of weeks. This is still a pain. I would not have had to do it with my old 1999 Explorer...

 

Hello -

my mother just bought a new 2021 RX 350 in December. After about a month the battery started dying every few days. I just assumed that she was leaving something on that was draining the battery but after boosting it a number of times I'd check and see nothing left on. It was brought to the dealer and they said that everything is fine. Just wondering if anyone else has had this problem or may know of something that's causing this to happen. Thanks!

 

Leave them the car overnight and tell them to start the car the day after.

 

How often is Mom driving the new car??

 

Not very often at all. Once or twice a day.

 

How for or long does she drive it each day. If only a few minutes each day it might be that the battery does not get enough time to recharge.

 

The following copied from a Lexus PDF:
Lexus Vehicle Battery Maintenance

Lexus Vehicle Battery Maintenance The primary battery in your Lexus vehicle needs to remain fully charged to start and drive your vehicle. If not used regularly, it may reduce its performance and life. In the worst-case scenario, it can even leave you stranded. There are conditions including how long it is stored without being driven, as well as parasitic draw that can impact the battery’s available charge. Because of these factors, battery maintenance is required to ensure proper operation and optimal battery life.

Under the current COVID-19 environment, some people may not be driving their vehicles for long periods of time. There are three methods of battery maintenance:

1. Driving the Vehicle/Starting the Engine This is the easiest method. The vehicle is used weekly after non-use. Driving the vehicle for 30 minutes with all accessories off for at least 10 miles above 30 MPH will maintain the battery’s charge. If you are unable to drive the vehicle, start and run the engine in an open-air environment for 30 minutes with all the accessories off.

2. External Battery Charging Connect an external battery charger (also known as a battery “tender” or “trickle charger”). This device hooks up to your car battery on one end and plugs into a wall outlet on the other. It delivers enough electrical power to prevent the battery from discharging. For instructions on how to safely connect a battery charger, contact your Lexus dealership. Your local Lexus dealer may have an external battery charger available for purchase at a nominal cost. Alternately, you can purchase an automotive battery charger online.

3. Disconnect the Battery Cable Parasitic draw or parasitic drain is a term for an electrical component consuming electricity when the vehicle is not used, even after the vehicle has been shut off. The average vehicle can have as many as 50 computers that all use small amounts of electricity. Over time, this can cause the vehicle's electrical system to function improperly and the vehicle may exhibit the following symptom: a persistently dead battery. To reduce parasitic drain on vehicles in storage for a week or longer, the negative (-) black colored battery cable may be disconnected to eliminate the battery discharge. Note, when the negative (-) battery cable is reconnected, you will need to check and reset electrical components such as the clock, radio settings, seat memory, etc.

 

One possibility is excessive parasitic drain. All cars today have a small amount of battery drain while they are shut off. That current should not exceed .05 amps. You need to have someone check it for you. It is also possible you have a bad battery. It happened to me some years ago I bought a brand new battery and it was junk from day one.

 

I suspect a defective battery. If your Mom is driving twice a day, even briefly, 10 minutes in each direction, that should be enough to keep a new battery charged up. If all the dealer did was attach a volt meter to the battery, then of course it would show good. Find out if they are checking the acid with a hydrometer, which would reveal a dead cell. Another test is the one that puts a load on the battery for a specific amount of time. I don't recall the name of the test. BTW, what are the symptoms of the battery dying every few days? Slow cranking? Clicking when pressing the start button? Are you parking outside in sub-zero temps? I drive my Avalon once a week on a short errand and the battery is ok. It's new. Hope this helps. Ray A.
PS By any chance, is she leaving the door ajar? Just an afterthought.

 

Could have sworn that batteries were SEALED.

 

Hi, not sure how this reply system works but hopefully you get this message. I purchased a RX450HL last June and within 3 weeks the battery started to fail. Local Lexus garage charged it to full 2 times but still same issues. Then on my final angry call they received the vehicle for overnight check and came to conclusion that it was a faulty battery. Took 3 weeks to import a new one from Japan and finally got it changed. Since then I've had no problems. Hope this helps.