Makes me wonder if they fixed the issue on later vehicles.

 

Given Lexus, I'm not holding my breath they did anything at all. Not having the battery dying during summer doesn't prove anything whatsoever. My car had survived 26 days of parked state when I was on vacation during winter, and died 1 week later (a week full of driving) when the temperature dipped to 4 C.

Only the voltage data from the battery monitor (such as I did in post #70 and others have done more directly), actually showing the charging voltage during driving would convince me if any changes were even attempted.

 

I changed my trickle charging method to a OEM direct connect plug, I now leave it plugged in when ever I am parked in my garage. Cheers

 

Did the same thing. Even with light driving I find my RX350 battery almost always accepts additional power from my battery maintainer. It makes me wonder if the charging system designed-in is sufficient for the power needs of this vehicle.

 

Assuming you are in the US, how did you manage to get the "OEM direct connect plug" ? And given you don't have a hybrid of PHEV, are you just trying to play it safe, or did you actually have a dead battery situation ?

 

I am in the US, and just trying to increase the life of my battery, and avoid unpleasant surprises. We are often gone a month at a time and sitting un-driven and uncharged for that long is a known killer for batteries. So I hook up a Battery Tender maintainer if not using the car for a few days or more. Do the same thing with our other cars, and been using Battery Tender brand for decades. The other forum member mentioned OEM direct connect plug - as far as I can tell that is just a different brand maintainer - don't think it is OEM. I do hook the removable cable directly to my battery. When I want to use it, a 3 minute job to plug in the maintainer. It's probably all a waste of time. .

 

I agree that only voltage monitor data would convince me of a fix. It's just that our vehicle will fall below 90% unless I proactively charge via an external charger or use remote start or stay in park extensively.

Lexus is known to quietly make changes then only provide the fix to existing owners if one complains about the issue. Exmple being the door open button that freezes in cold weather.

 

Update to my post: Today, my battery monitor showed 78% when I checked it before heading out...so, definitely no fix. Honestly, I don't expect any fix to come for the issue. My limited internet research indicated that poor 12V battery charging is certainly not limited to Lexus, and none of the other manufacturers seem to be too concerned about fixing it either...at least not so far.

 

I'm wondering if the State-of-Charge value provided by the usually found battery monitor is assuming its measuring a run-of-the-mill lead-acid battery, while the Panasonic OEM battery is actually having a lower resting voltage as "normal" - and therefore the SoC values and alarms by the battery monitors is actually more pessimistic than should be appropriate for the Panasonic deep-cycle/lower-voltage battery that comes from the factory.

So the real proof of a fix has to be voltage read-outs during driving, which if showing a higher than currently known charging voltage, would have to be the only credible evidence of a fix.

If Lexus were to indeed send out fixes surreptitiously only to specific users who complain, then it would be like the "secret" menu of In-and-Out Burgers - where one would have to first find out that secret TSB/Fix reference from this forum, and then go beg the dealer giving that secret code for the fix (?)

I found that Tesla (not that I'd buy one) has actually started shipping Lithium-Ion 12 V batteries. Wonder if that has to do with this issue ?

Yes, while the 12 V battery issues is pretty prevalent across the spectrum, others have reported in this forum how Hyundai (and I've read, BMW) mitigate the problem almost completely by having an automatic Battery-Management-System that charges the 12 V battery proactively from the traction battery whenever necessary. It seems Lexus doesn't have any BMS for the 12 V at all, and of course, would rather cruise on its reliability reputation rather than live up to it by fixing this issue.

 

Based on the fact that the charging system puts out standard flooded-lead-acid charging voltage, when it is actually charging, I feel that the battery voltage is standard as well. I also base that on the fact that the charging times, on an external charger, correlate to the rated capacity of the battery, from a given voltage.

 

Was done to save space, weight and increase reliability.
Fixing this issue would require every vehicle have a dealer visit to get one or more modules firmware flashed that's never going to happen.

 

Well, assuming that’s what it takes technically, then a safety-mandated recall or class-action is what it would take to certainly make things happen.

(A lot happened to/by VW after diesel-gate, relative to which such a legal mandate would be peanuts)

 

A maintainer always goes into charge mode when you first hook it up, even if the battery is fully charged. Remember that its goal is to float the cell, and that's a stepwise process.

If you get a charger (not a maintainer) like a Schumacher brand, it will come with a charge level meter on it so you can actually numerically see what its doing, how the battery charge level is advancing while being charged.

 

That's the game auto makers play (all of them) they weight the legal costs and decide, or until they are forced to recall.

 

I realize that the 12V battery issue on both the hybrids and plug-in hybrids has been discussed here ad nauseam but, I have a new observation which I have just found. My wife and I just returned Friday evening following an eleven day trip to DC, VA and NC. I decided to do an experiment on both of our 450h+ vehicles prior to our departure. I left one vehicle plugged into one of my float chargers for the entire duration and the other with no charger attached. Upon our return, my RX450h+, which was on float, showed 100% SOC, as expected. My wife's NX450h+ was showing an 88% SOC after the eleven days! This was far higher than I had expected. Even when we are home, I have seen the SOC drop as much as 25-35% or more in a day or two. As is the norm, I had deactivated all of our fobs and/or placed them in a Faraday box for the entire duration of our trip. I suppose that the 12% loss was most likely due to the daily cycling of the leak detection pump in the EVAP system. Obviously, with neither of our two iPhones close by, there was no data communication with either vehicle and/or the Lexus mothership.