$219.00 plus tax

 

Mordin, if you said that one day all is fine and the next day not enough current to unlock the doors? There is a bad electrical connection somewhere. Batteries don't drain that fast.

 

I am looking for the experience of others with their RX350 batteries that discharge too quickly when the car is not driven for multiple days. I have asked about this before but I have some more information and perhaps there are new people and/or new experiences by others.

I have a 2020 RX350 with a battery that was replaced by the dealer in June 2020. If I *fully* charge the battery and then measure the voltage every 24 hours, I get the following:

day 0; 12.66V; 100%

day 1; 12.46V; 80%

day 2; 12.40V; 75%

day 3; 12.35V; 70%

day 4; 12.31V; 65%

day 5; 12.27V; 60%

day 6; 12.24V; 55%

The right column is the percent charge left in the battery based on charts that show the relationship between voltage and charge for a normal lead-acid car battery. Note that at 12.24V there is still plenty of charge to start the car. However, the battery continues to discharge at the same rate beyond the sixth day and you don't want to allow a lead-acid battery to discharge below 50% too often.

Has anyone else done measurements similar to the above? What did you get? Any information would be greatly appreciated.

Based on the battery specs, it's storage capacity is approximately 50 amp-hours (Ah). Over six days, 45% of the charge is gone, i.e., 22Ah. Six days is 144 hours. Hence, the average parasitic current draw was 22/144 = 152mA. This is three times higher than what it should be (up to 50mA).

The first day is clearly an outlier. If it's ignored, 25% of the charge is lost in five days (day 1 to day 6). This translates to an average parasitic current draw of 12.5/120 = 104mA. This is still two times higher than what it should be.

The average current draw of the car was measured to be 32mA. Hence, something weird is going on.

 

Interesting that the dealer replaced the factory battery in June, 2020. I think that's your red flag -- it looks like the battery was believed to be a problem, but was not the problem after all. I think I would get Lexus USA on the phone, and in a very pleasant and polite manner, explain to them that all indicators are that there is a problem with the car, that was first thought to be a defective battery, but upon detailed examination and the passage of some time, appears to be something more subtle, where the car is pulling excessive current while parked. Maybe they can find (or send) a more experienced technician who can perform diagnostic testing and figure out where the electrons are going.

 

You definitely have a parasitic drain from something. Basically they have to attach an ammeter to measure the current draw and disconnect or pull fuses until the drain disappears. Might be more involved than that, but basically that's what has to be done.

 

I have already gone through Lexus on this and a factory rep (Lexus technical specialist) has looked at the car. He confirmed my measurements over a two day period. However, he claims that this is normal. I talked with the guy in person. He would not engage regarding the specifics of the analysis I have done, He just kept saying "there is nothing wrong with the car", "the car needs to be driven more" and "use a battery tender". All this sounds to me like well-rehearsed, lawyer-trained responses.

This is the reason I am looking for similar measurements by others. I want to know whether this is indeed what can be expected from an RX,

 

The parasitic draw has been measured by a "Lexus technical specialist" to be 32mA (which is under 50mA and thus perfectly fine). The problem is that he would not engage regarding the analysis and claims that "there is nothing wrong with the car".

This is why I am looking for what other people have observed with their cars.

 

My wife has been working from home for 10yrs, and had a 2016 & now a 2020 RX350. Both cars has stayed in the garage not driven sometimes up to 2 weeks. No battery tender and never had to replace the battery in either.
Very disappointing to hear that some Lexus service locations make excuses instead of finding solutions to repair a problem. When you said Fully charged the battery was that by using a charger or just driving. Also I've heard having the keyfob close by could cause a slight drain while parked. I'm just throwing stuff out there....

 

At the rate of my battery discharge (5% per day after the 20% on the first day), two weeks gets you to 15%. The threshold for being able to start the car is supposedly 20%. Thus, it is possible that my car would also start after two weeks. The key question is how much your battery is discharged in those two weeks? What is the voltage at the end of the period? With a lead-acid battery, too many discharges below 50% supposedly kills the battery.
The fact that you didn't have to replace the battery is definitely an indication that the battery in your car was probably not discharging as fast as mine.

I tried fully charging with a charger, driving on the freeway for 30min, as well as both -- the battery really is fully charged and the results are consistent. The keyfob comment is correct -- I am very careful to keep the keyfobs very far away from the car.

It's actually worse than just the "Lexus service locations" (the dealership). I caused enough noise that I got a "factory rep" (Lexus technical specialist) to look at the car. Unfortunately, he gave me the same BS as the dealership.

 

Quote:

Originally Posted by rx20info

At the rate of my battery discharge (5% per day after the 20% on the first day), two weeks gets you to 15%. The threshold for being able to start the car is supposedly 20%. Thus, it is possible that my car would also start after two weeks. The key question is how much your battery is discharged in those two weeks? What is the voltage at the end of the period? With a lead-acid battery, too many discharges below 50% supposedly kills the battery.
The fact that you didn't have to replace the battery is definitely an indication that the battery in your car was probably not discharging as fast as mine.

I tried fully charging with a charger, driving on the freeway for 30min, as well as both -- the battery really is fully charged and the results are consistent. The keyfob comment is correct -- I am very careful to keep the keyfobs very far away from the car.

It's actually worse than just the "Lexus service locations" (the dealership). I caused enough noise that I got a "factory rep" (Lexus technical specialist) to look at the car. Unfortunately, he gave me the same BS as the dealership.

Something definitely isn't right with your RX. I would figure a diagnostic test via OB2 port should display voltage drop after monitoring a few hours. The car manufactures has proprietary software to access more setting and run more extensive tests. Then they can share and compare with your results. I have a pretty good scanning tool, and some of these tests are grayed out that I use on my other cars. I just don't understand the unwilling to come up with a solution unless they already know especially with your helpful data.

Somebody else here has posted to start unplugging fuses and do your measurements. At least you can narrow down the area of the drain Since you my be on your own with this issue not sure if our batteries are AGM's or not, but they hold charges longer. That's what I have in one of my cars.
Keep us posted...

 

The RX350 battery is definitely not AGM. It is a conventional lead-acid battery. Based on the specs written on the battery (reserve capacity of 133), the storage capacity is approximately 50Ah. I was told that Lexus does not use AGM batteries of the form factor needed for the RX350 (24f). Obviously, if I purchase a third-party battery, Lexus would just say that the problem is with the battery.

At this point I cannot "fight" Lexus without additional clear evidence. They claim that what I am observing is normal. They don't have any real argument to refute my analysis so they just say all kinds of random nonsense.
The problem is that I have so far not been able to come up with even one person who says something concrete like "I have a 2019 RX350. I measured the voltage after 20 days and it was 12.3V" or "I have a 2020 RX350 and I was able to start it after it sat for 23 days" or ...

The other possibility is to consult a true expert who does not work for Lexus. I am in Los Angeles so it should be possible to find such a person reasonably close. I just need to figure out how.

 

My two cents: first, all batteries self-discharge. Normally in a healthy battery this would take months before the battery is depleted, but I think it’s possible to have a defective battery that passes the CCA test and cell specific gravity tests, yet self-discharges significantly faster than normal. I also don’t think there is an easy way for this self-discharge to be accurately measured, so the dealer or repair shop is just going to measure the stuff they can measure and pronounce the battery “good”. The parasitic drain that was measured is the load that the car is putting on the battery and does not include the battery’s internal current drain.

Second, today’s alternators don’t really put out a lot of juice, especially when idling. This was one step manufacturers took to try to eek out every bit of MPG gains they could. Meanwhile, cars have ever-increasing current demands. So someone that drives in city traffic may not really be recharging the battery much at all. My own experience here: about a decade ago I did a short stint in the engineering offices at another auto manufacturer here in the US. One of my colleagues was tasked with investigating battery warranty issues, specifically customers were complaining that brand new cars were getting dead batteries almost immediately. His conclusion was that the down-sized alternator, coupled with short stints of city driving, never charged the battery up and that in fact the car would wind up with less energy in the battery than before the owner started up the car to drive to work.

So my take: rather than spending a ton of money with experts and other shops, just buy a new battery. Whether from Lexus or some other reputable place, even Autozone. That rules out any battery issues. Then get a battery tender and once every few days plug it in. Sure it’s a brute-force solution but I periodically put my truck, which is driven infrequently, on the battery tender and it’s not too much of an inconvenience.

 

I agree with almost everything. I also thought about the possibility that the battery is bad despite passing the CCA test. However, Lexus will not replace it unless it fails their test and the car is still under warranty. One reason to think that it's not the battery is that the dealer replaced the battery six months after I purchased the car. I believe that the previous battery died due to the excessive discharge problem.
I also agree about the charging system. However, it is not relevant in this case since I charge the battery with a 4A charger/tender for 24 hours -- the battery is fully charged before my measurements.

If the problem is inherent in all modern RX350s (perhaps even in all/most modern cars in general), I'll live with it and charge the battery with a charger/tender once per week. However, if other modern RX350s maintain their charge longer, I would like to bring my car up to that level.

Presumably, an experienced unbiased expert would be able to tell me whether what I am observing is normal. If it is, the story ends there. If it's not, there is a point to investigate further. The question is how to find such an expert...

 

We have a 2021 RX350 AWD. We don't drive to work (retired). We only drive to shop nearby once in a while. The car sits in the garage a lot. We've driven 4,000 miles in 9 months. We never have had a problem with the battery. I know this is of no help to you because you are looking for others with your same problem. We wish you success with your troubleshooting. Please let us know your solution.

 

Thanks! Actually, I am not looking for people with the the same problem. I am looking for people who do *not* have the problem. 4,000 miles in 9 months is actually quite a bit of driving (100 miles per week). If I was driving that much consistently, I would definitely not have the problem either. What is the longest time you have let the car sit without driving it at all?